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Electrode Receptacles and Enclosures

Posted By Paul R. Davis, Saturday, January 01, 2000
Updated: Monday, February 11, 2013

There are other factors that complicate the situation. Some components are UL Recognized Components while others are UL Listed. UL recognized components are suitable for use only in an overall listed end use product. These recognized components are not suitable for use as field-installed units. Other products may carry a CSA Certification which may differ in some cases from a UL Listing. CSA and UL are both standards writing bodies. Verify the components that are allowable in your jurisdiction to be sure they are suitable for the intended use and acceptable to the AHJ. The rules here are not clearly black and white. There are some gray areas that require investigation.

Electrode Receptacle Terminology

There are housings, P-K housings, housings sold under the P-K name, which are standard #100, #200 and #300 borosilicate receptacle housings. There are electrode enclosures G Cups, GG Cups, G-2s, D-2s, 2UPs (a D-2 like housing) and myriad of boots, cups, and caps, which are referred to by the Code as electrode enclosures.

A commonly used term for the non-glass and ceramic electrode enclosures referred to as boots, cups and caps is "rubber-like.” Some prefer "polymeric” instead of rubber-like. Webster defines "polymeric” as "of or relating to a polymer.” The definition of "polymer” is "a naturally occurring or synthetic substance consisting of giant molecules formed from polymerization.” Rubber-like tells a better story.

Most rubber used today is synthetic. Most everyone understands rubber-like to indicate a flexible and pliable material. That’s the type material (a flexible and pliable material) referred to in this story.

Article 600—Electric Signs and Outline Lighting of the National Electrical Code underwent major changes in 1996. The most significant involved field installed outline lighting (commonly called border tubing). The requirements for border tubing fall under Part B of Article 600 (Field-Installed Skeleton Tubing). Misapplication of the requirements of Part B has caused numerous problems with border tubing, including fires caused by poorly installed neon, and the use of combustible electrode enclosures. Many of these rubber-like boots, cups, and caps were not UL Listed or Recognized.

The earliest edition of the Underwriters Laboratories Standard for Electric Signs that can be referenced for the story is March 1930.

The following was part of the UL Requirement before 1930, the exact date is uncertain:

Electrode Receptacles—129.It is strongly recommended that electrode receptacles be used.

130. Electrode receptacles for gas tubes shall, if used, be of a noncombustible, nonabsorptive insulating material.

131. Fiber, rubber, hot moulded shellac, or phenolic compositions are not considered suitable materials for electrode receptacles for ounting of high potential parts.

132. A rubber gasket may be used in connection with the mounting of an electrode receptacle.

133. A rubber gasket may be used around a gas tube in an electrode holder to prevent the entrance of dust, moisture, etc., provided the gasket is not depended upon for the insulation of the tubing and is not in contact with grounded metal such as the sign face.

134. An electrode receptacle shall not permit water to accumulate therein and thereby form a conducting path to grounded metal such as the sign face.

135. Each electrode receptacle shall be of substantial construction and shall provide means for reliability securing it to the sign face. Electrode receptacles shall not be secured to sign faces by means of sheet metal screws.

136. Each electrode receptacle shall be constructed so that, when installed, the spacing mentioned elsewhere in these requirements will be maintained.

This may seem like ancient history to some, but if every sign and neon installer followed these eight basic rules for neon installations, the amount of fires would be minimized and the reliability of the average neon system would be greatly improved. The removal from the 1999 NEC of "Electrode receptacles for the tubing shall be of noncombustible, nonabsorbent insulating material” for wet location situations, created a whole new set of problems.

Now back to the main subject at hand. There are a dozen varieties of glass electrode receptacles and enclosures available. Most of these are available from more than one manufacturer, and the others are available through at least three master distributors, and dozens of sign supply distributors.

The glass electrode receptacles (#100, #200 and #300 housings) are generic and are available from at least three manufacturers. The rubber-like electrode enclosures, polymeric boots, cups, and caps are not so generic. They are all different in configuration to some extent. They have different conditions of acceptability, and the conditions are not readily available in the exact form stated in the listing and/or recognition.

There are presently no polymeric or plastic boots, cups or caps to cover an electrode, straight or double-back that are UL Listed for wet locations. Be sure to note, this is UL Listed and, as indicated earlier, some of these products have CSA Component Acceptance for certain uses in wet locations. The conditions of acceptability with the CSA Component Acceptance are not absolute, so each product should be verified for specific uses with CSA. Contact CSA directly. As always, acceptability to the AHJ should also be verified. If in doubt, contact the local inspector or authority having jurisdiction and communicate.

CSA Component Acceptance Information

The old CSA Component Acceptance Mark is a CA connected like script. From Appendix E—CSA Marks, E.3: "The ‘old’ Component Acceptance Mark which indicates that a component has been accepted by CSA International on the condition that the use in an end-product is subject to further investigation.

"The mark is being phased out and replaced by the Component Marking, item E.9.15.”

The new mark is the standard CSA circular mark with an equilateral triangle at the lower right. From Appendix E—CSA Marks, E.15: "Component Acceptance Marking, intended primarily for factory-installed components, indicates that a component has been evaluated and accepted for specific applications and/or requirements, as stated in the accompanying literature.

Photo 1. In the early days, many housings were made of porcelain glazed ceramic.

In the early days, many housings were made of porcelain glazed ceramic. (See Photo 1.)

Photo 2 shows the manufacturer (KOLUX), Model No. 112, manufactured in U.S.A. and the voltage rating of 7500V. TRANSCO now has a porcelain glazed ceramic insert for the "P-K Type” Metal Clad Housing.

Photo 3 is another unusual housing made from borosilicate glass. The brass honeycomb component at the bottom of the housing is the contact for the electrode. The honeycomb replaces the spring contact in the #100, 200, and 300 styles. The electrodes used with this system had the equivalent of a nail about 1/2-inch long sticking out the end of the electrode where the wire is on current electrodes. This nail established the contact with the honeycomb brass device. The high-voltage power was connected to the wire projecting from the right side of the housing. This was covered by a separate piece of heat resistant glass (not shown) to insulate the connection from objects near the terminal point. The housing was held in place with a friction fit metal ring in most cases.

Photo 2. The manufacturer (KOLUX), Model No. 112, manufactured in U.S.A. and the voltage rating of 7500V.

Photo 4 is looking directly into the housing from the top. The honeycomb brass contact, and the nail in the electrode, provided a foolproof method of connection. You can see the electrode at the left of Photo 5. This housing and electrode are from the mid to late 1920s.

You have all heard of Pyrex glass. All Pyrex is borosilicate, but not all borosilicate is Pyrex. One blend of Pyrex, No. 7740 has a softening temperature of 820º C, while common borosilicate has a softening temperature of only 593ºC.

This of course is compared to most of the rubber-like materials, which are rated at a maximum of 105º C. The borosilicate will not burn, and the polymeric materials do melt and/or burn.

Photo 3. Another unusual housing made from borosilicate glass.

There is another major factor in the rubber-like electrode enclosures vs. glass electrode receptacle debate. All glass housings, including all the G Cup series must be securely attached to the background (sign or building) to meet UL Requirements. None of the rubber-like boots and cups presently has to meet this same requirement. This attachment to the background is critical to both safety and reliability.

All of the glass electrode enclosures are UL Listed for dry, damp and wet locations, except for the casino bushing, and it is UL Recognized. D-2 housings are not UL Listed for wet locations either. The 2UP is the only "D-2 Type” which is UL Listed for wet locations.

Photo 4. Looking directly into the housing from the top. The honeycomb brass contact, and the nail in the electrode, provided a foolproof method of connection.

The G Cup is the only UL Listed housing for double backs which has a wet location listing when installed with proper orientation. See Drawing – 19R and Drawing – 23a to see how they must be installed to meet the conditions of the listing. The GG Cup shown in Drawing – 50 is also the only receptacle available for this type installation which is UL Listed for wet location. The 45º angular positioning on both of these devices is part of the listing requirement.

The G-2 Cup in Drawing – 47 is to be used in a channel letter with a housing type transformer. This is required in 600-23(b)(2). Field wiring as required for boots and caps is not allowed with housing type transformers. A D-2 [see Drawing – 52] or the 2UP [Drawing – 52(b)] can also be used for this.

The glass housings are numbered as follows, and you will find drawings of each in this story.

Photo 5. You can see the electrode at the left of Photo 5. This housing and electrode are from the mid to late 1920s.

The most common housings, prior to the advent of the rubber-like products, were the #100, #200 and #300 borosilicate housings. In the early days, they were all Pyrex.

The #100 is the largest diameter [Drawing – 55 (d)] and requires a panel opening of 1-3/4 inches. The #100 has a spring contact to connect the electrode to the secondary wiring system. This housing, allows water to wash the bugs and dirt out of the housing, the best of all the glass panel mounted housings except for the #300.

Drawing 19R. The G Cup is the only UL Listed housing for double backs which has a wet location listing when installed with proper orientation. See Drawing 19R and Drawing 23a to see how they must be installed to meet the conditions of the listing.

The #200 housing comes in two lengths. It is identical in basic configuration to the #100, but is smaller in diameter, and requires only a 1 5/16-inch panel opening. The #200P is 3.125-inches in overall, compared to 4.563-inches for the #200. The length is the only difference between the #200 and #200P.

The casino bushing (Drawing – 54) is the smallest glass housing available and, as pointed out earlier, is UL Recognized, not UL Listed. The panel opening is only 1-inch in diameter. The electrode connection to the secondary is made with a twisted wire connection, or better yet the connection can be made with a open end crimped type splice cap. This type of crimped connection is much more reliable than a twisted wire connection.

Drawing 23a. The G Cup is the only UL Listed housing for double backs which has a wet location listing when installed with proper orientation. See Drawing 19R and Drawing 23a to see how they must be installed to meet the conditions of the listing

The #300 and #300P probably cause the least problems of all the housings from #100 to #300 series of glass housings. They are open back as you can see in Drawing – 55(b). The #300 makes the secondary connection with a spring contact, and the #300P uses a spring clip. The positive connection of the spring clip to the electrode wire is by far the best way to go. With this method there is no room for error. It’s connected securely and misalignment doesn’t matter. With spring connections, misalignment is always possible, and can cause problems.

Drawing 50. The GG Cup shown in Drawing 50 is also the only receptacle available for this type installation which is UL Listed for wet location. The 45º angular positioning on both of these devices is part of the listing requirement.

Using electrode caps is a good approach. This provides a much larger surface area for contact between the spring and the electrode. The electrode button can easily slip by the spring, and cause an arc. The arc is contained in the glass housing, and rarely, if ever, will cause a major problem like a fire but, simply put, the electrode button is just not as reliable as the electrode cap. (Arrow 2 points to the electrode cap on the neon tube in photos 1 and 5.)

Last, but not least, is the P-K Type metal clad housing [Drawing – 55(c)]. This is probably the most maligned electrode receptacle in the neon industry. It has been wrongly blamed for more problems associated with neon installations. The improper installation and connection of the device is, and has always been, one of the major problems.

Drawing 47. The G-2 Cup in Drawing 47 is to be used in a channel letter with a housing type transformer. This is required in 600-23(b)(2). Field wiring as required for boots and caps is not allowed with housing type transformers.

Here’s a little bit of history about the P-K. The original patent application was filed March 12, 1947. Patent 2,488,065 was issued to C. M. Peterson on November 15, 1949.

From the Patent: "The invention relates to high tension terminal housings and has particular reference to insulator thereof.

"The principal object of this invention is to produce a housing and an insulator for high tension use, which will prevent the corona effect between the high tension cable and its conduit at a point adjacent the terminal.

"A further object is to produce a device which may be used with ordinary equipment now in use without materially altering its construction.

"A still further object is to produce a device which is economical to manufacture, easy to use and one which complies with all standard insulating requirements.”


Drawing 52. This is required in 600-23(b)(2). Field wiring as required for boots and caps is not allowed with housing type transformers. A D-2 [see Drawing 52

One improvement on the original patent was the introduction of a metal clad housing with a one-piece flange to fasten the shell to the channel building, letter body, or sign cabinet. This provides a positive bonding connection between the shell and the letter or cabinet. The flange will also hold the housing tightly to the building. Other metal clad housings have a two-piece flange device which clamps around the basic metal shell of the housing, but are somewhat more difficult to install.


There are many opinions about what’s best when it comes to neon installations, and especially neon receptacles. The facts outlined here are based on field experience with the various components. Safety and reliability should always be priority one even though, today, too many times it is not a priority.


Drawing 52(b). This is required in 600-23(b)(2). Field wiring as required for boots and caps is not allowed with housing type transformers. A D-2 [see Drawing 52

The lack of proper bonding and grounding of the high-voltage part of a neon system, is most often the primary cause of poor reliability and fires. If all metal conduit is used, the bond is hard to lose. When PVC and other nonmetallic materials are used in the conduit system, it’s necessary to run a separate bonding conductor. This part of the equation becomes very difficult, especially with the changes to the Code in 1999.


The 1999 NEC added the following requirement for nonmetallic conduit.

"600-7. Grounding. Signs and metal equipment of outline lighting systems shall be grounded. Listed flexible metal conduit or listed liquidtight flexible metal conduit that encloses the secondary wiring of a transformer or power supply for use with electric discharge tubing shall be permitted as a bonding means in lengths not exceeding 100 ft (30.5 m). Small metal parts not exceeding 2 in. (50.8 mm) in any dimension, not likely to be energized, and spaced at least 3/4 in. (19 mm) from neon tubing shall not require bonding. Where listed nonmetallic conduit is used to enclose the secondary wiring of a transformer or power supply and a bonding conductor is required, the bonding conductor shall be installed separate and remote from the nonmetallic conduit and be spaced at least 1 1/2 in. (38 mm) from the conduit when the circuit is operated at 100 Hz or 1 3/4 in. (44.45 mm) when the circuit is operated at over 100 Hz. Bonding conductors shall be copper and not smaller than No. 14. Metal parts of a building shall not be permitted as a grounded or equipment grounding conductor.

Drawing 54. The casino bushing (Drawing 54) is the smallest glass housing available and, as pointed out earlier, is UL Recognized, not UL Listed. The panel opening is only 1-inch in diameter.

"FPN: Refer to Section 600-32(j) for additional restrictions on length of high-voltage secondary conductors.”

Accomplishing the feat of stringing a bonding wire "1–1/2 in. (38 mm) from the conduit when the circuit is operated at 100 Hz or 1 3/4 in. (44.45 mm) when the circuit is operated at over 100 Hz” is not a simple operation. The bonding wire is exposed and susceptible to physical damage.

One other critical part of this situation here is the fact that the most important part of the high-voltage system (the bonding wire, the path to a safe ground.) is 1 1/2 to 1 3/4 -inches away from the components that can start the fires.

Neon systems are not all that difficult to install. Good planning and following the rules of the game are the two obvious keys to a safe and reliable installation.

Well made and correctly installed neon will last for 30,000 plus hours. It will be virtually free from fire hazards. If getting someone’s attention is important, brightly illuminated neon at night is one of the best answers.

Read more by Paul R. Davis

Tags:  Featured  January-February 2000 

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Determining Proper Loading for Neon Sign Transformers

Posted By Telford Dorr, Saturday, January 01, 2000
Updated: Monday, February 11, 2013

Neon sign transformers differ from most other types of transformers one is likely to encounter. Unlike a more conventional transformer, for normal operation a neon sign transformer is specified to operate a minimum, as well as a maximum load. Why is this? To understand this requirement, we must look at what makes a neon sign transformer different from other types.


Figure 1. This regulation is accomplished by inserting a ferrous magnetic shunt (fig. 1) into the transformer core, such that the magnetic flux from the primary winding has an alternate (although high impedance) path around the secondary winding.

Neon tubes require a high voltage at a low current to operate. This power is supplied by a specialized transformer. Secondary voltages typically range from 1,000 to 15,000 volts, and secondary currents range from 20 to 60 milliamps (and higher, for large diameter "cold cathode” tubing). The current passing through a neon tube needs to be limited by some means, otherwise once the tube lights, the current will rise to an excessively high value. This regulation is accomplished by inserting a ferrous magnetic shunt (fig. 1) into the transformer core, such that the magnetic flux from the primary winding has an alternate (although high impedance) path around the secondary winding. As the current draw on the transformer secondary winding increases, more primary magnetic flux diverts1 through the magnetic shunt. While this gives the transformer a poor voltage regulation characteristic, it also tends to keep the neon tube operating current reasonably constant. We may electrically model this type of transformer as a conventional transformer which has an inductor in series with each of its high voltage secondary leads2 (fig. 2).

Figure 2. We may electrically model this type of transformer as a conventional transformer which has an inductor in series with each of its high voltage secondary leads

Note that some transformers may have more than one secondary winding and more than one secondary shunt. If a transformer has two secondary windings, the midpoint connection between the secondaries may be grounded to the transformer case. Depending on the exact configuration of shunts and secondary windings, a transformer may be referred to as having either a "balanced” (fig. 3) or an "unbalanced” (fig. 4) design, and this in turn determines what types of secondary wiring methods may be used. Refer to the transformer manufacturer’s literature for more details on this.

This constant current nature of neon sign transformers allows one to greatly vary the tube loading on a transformer. Unfortunately, one can radically misload a transformer and it will still appear to work, in the short term. Long term, transformer failure will usually result. For any given transformer, the tube load should fall within specified limits. It must not be too high or too low3. The question is, how does one determine the proper loading?

Methods of Determining Proper Loading

Figure 3. Depending on the exact configuration of shunts and secondary windings, a transformer may be referred to as having either a "balanced" or an "unbalanced" design, and this in turn determines what types of secondary wiring methods may be used.

There are several answers to this question. The most commonly used method is by reference to manufacturer supplied loading charts. These charts indicate the minimum and maximum total length of neon tubing that may be used on a given transformer, as a function of the tube diameter, gas fill pressure and type of gas used (typically either straight neon or an argon/neon/mercury vapor mix). When using a chart, one deducts some amount of tube length for each pair of electrodes used (which occurs when multiple tubes are wired in series.) Other rules-of-thumb allow compensation for connecting tubes of varying diameters and gas fills in series. While this loading method seems straightforward and simple enough, and is certainly a good place to start in determining proper transformer loading, it does not always produce the desired results. This is because neon tubes may not exhibit the standard characteristics the loading charts are based on, due to processing variations and other factors. Therefore, we need to understand a little more about transformer characteristics, and look at some alternate loading techniques.

Checking Transformers

In the USA, neon sign transformers are rated primarily in terms of their open circuit secondary voltage and their short-circuit secondary current. While these ratings are specifically intended for use in calculating proper loading, they are also useful in determining if a neon sign transformer is functioning properly. The open circuit voltage may be measured with a good voltmeter, equipped with a high voltage probe. Typically, the higher voltage transformers (6000 volts and above) have their secondary winding midpoints grounded to the transformer case. The voltmeter common lead is connected to the case and a voltage measurement is made at either secondary terminal. The sum of these readings should equal the secondary rating. Be sure to measure the primary voltage, as the open circuit secondary voltage will vary proportionally with the primary voltage.

Secondary current may be measured by connecting an AC milliamp meter directly across the secondary terminals. The transformer will withstand this short circuit for a reasonable amount of time, because the magnetic shunts previously described allow what would otherwise be seen as abuse to be tolerated by the transformer primary winding. Again, the current reading should be reasonably close to the secondary short circuit value on the transformer rating plate.

Figure 4. Depending on the exact configuration of shunts and secondary windings, a transformer may be referred to as having either a "balanced" or an "unbalanced" design, and this in turn determines what types of secondary wiring methods may be used.

Be sure to check the manufacturer’s literature for their specific recommendations on testing SGFP type transformers, as the above general test methods may not work properly.

This brings us to a second method of determining proper transformer loading. For US made transformers, the typical transformer secondary operating current is approximately 80 percent of the rated short circuit current. For a transformer rated at 30 mA, this would be approximately 24 mA. We can connect a milliamp meter in series with a transformer’s tube load and measure this current. Various manufacturers make high voltage milliamp meters specifically for this task.

European Methods

I am told that in some areas of Europe, transformers are specified somewhat differently than in the USA. Typically, a transformer is rated in terms of its open circuit secondary voltage, its operating secondary current, and its "G” factor. The "G” factor is the desired ratio of loaded to open circuit secondary voltage. Typically, the "G” factor is around 0.5 (although this may vary), meaning for example that a transformer rated at 9000 volt open circuit should operate with a tube load connected at around 4500 volts. This may be measured conveniently with a voltmeter equipped with a high voltage probe. This is the preferred method of checking the loading on a European transformer, and in practice is somewhat easier and more sensitive than measuring the tube operating current. This method is starting to catch on in the USA as well. Unfortunately, US manufacturers don’t specify the "G” factor, but typically a value of 0.5 may be assumed.

One quick note here: when replacing a European transformer, the "G” factor must be taken into account. A replacement transformer with a different "G” factor will not operate a given tube load properly, even though its rated open circuit secondary voltage and operating current may be the same as the that of the original transformer.

Choosing a Loading Check Method

One would think that by using a loading chart in combination with measuring the secondary operating current and voltage that correct tube loading may always be determined. Unfortunately this is not always the case. There is one more variable in the mix: stray capacitance. This capacitance results from the close proximity of high voltage secondary wiring to its enclosing conduit (or other grounded metal objects), and between the neon tubing and the sign sheet metal. It is desirable to minimize this capacitance as much as possible. This means that any secondary wiring operating at high voltage relative to ground should be kept as short as practical, as capacitance varies directly with wire length. Various standardized wiring techniques, such as "mid-point return” and "virtual mid-point” have been devised to accomplish this goal. Both of these techniques involve keeping the wiring between the transformer and the electrodes on the first tube as short and direct as possible. Needless to say, the wiring techniques used must comply both with those methods allowed by the transformer manufacturer and with methods allowed by the NEC (for US installations), or with the appropriate European regulations for installations done there.

So what happens when capacitance intrudes in a neon installation? Two things, both bad. First, capacitance tends to counteract the current regulation of the neon sign transformer. Specifically, it tends to cancel the inductance in the secondary circuit of our previously described transformer model. This can cause excessive secondary, and thus, tube current. Unfortunately, installers tend to counteract this effect by adding additional tubing load to the transformer, or by selecting a smaller transformer. While this tends to restore the operating current, it is at the expense of operating voltage, which tends to rise excessively, leading to transformer failure. This is why both the operating voltage and current should be checked.

With some types of NEC 600-23(b) SGFP type transformers, the stray capacitance seen by either transformer secondary terminal should be similar. An imbalance may be interpreted by the protection circuitry inside the transformer as a fault, causing "nuisance tripping.” One of the best ways to avoid this situation is to insure that the GTO wires connected to either transformer secondary terminal be reasonably equal in length, as well as keeping them as short as possible.

Second, stray capacitance in combination with higher voltage transformers (typically units over 9000 volts) operating neon-filled tubes may invite transformer secondary circuit oscillations. These oscillations sometimes manifest themselves as flickering tubes and "buzzing” transformers, and are extremely destructive to both the transformer and to the high voltage wiring. Neither a voltmeter or a milliamp meter will conclusively detect this condition. Using an oscilloscope4 equipped with a high voltage probe, these oscillations may be easily seen. Other than reducing the capacitance as much as possible by mechanical methods, the best solution to this problem is to re-layout the sign wiring to use lower voltage transformers. This will, of course, require using more transformers to do the job.

Solid State Transformers

We have neglected to include so-called "solid state” transformers in our discussions of proper loading. This is because the operating frequencies used by these transformers preclude the use of regular voltmeters and milliamp meters, as they do not function well at these frequencies. The oscilloscope still works well, but few sign shops have them. On the other hand, most of these transformers are designed to operate with widely varying loads. When using these transformers, it is best to carefully follow the recommendations in the manufacturers’ data sheets.


Before publishing, this article has been passed for review to the members of the INA "Codes and Installation Forum.” I would like to thank everyone who reviewed this article for content and accuracy. Your assistance is greatly appreciated.

1 This is a bit of a simplification, but for purposes of illustration, it’s close enough.

2 Specifically, this is a model of a "balanced” midpoint grounded type of transformer. See figure 3 for a physical illustration.

3 A note on terminology: sign installers refer to a transformer as being "overloaded” or "underloaded” with tubing. Unfortunately, this refers to the length of tubing connected, not the electrical condition, which tends to be the opposite of that of the tubing. This is to say, when a transformer is "underloaded” with tubing, the transformer tends to draw excessive primary winding current.

4 Unfortunately, this type of equipment has been, in the past, both expensive and awkward to use in the field. Newer compact / portable equipment coming into the marketplace may make this measurement technique more practical in the future.

Read more by Telford Dorr

Tags:  Featured  January-February 2000 

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Neon Tubing Secondary Wiring Methods

Posted By George Doll, Saturday, January 01, 2000
Updated: Monday, February 11, 2013
This article is intended to address a few of the common neon installation challenges associated with the secondary wiring from the transformer or power supply to the electrodes, as observed by a member of both the life safety and neon communities.

Secondary wiring methods as required by the National Electrical Code, Section 600-32

A common misunderstanding is that standard 600-volt twist-on wire connectors can be used to make high-voltage connections. This is not true; these types of connectors may not be used for these connections, according to Code. There are listed high voltage splice termination enclosures suitable for this purpose. High voltage GTO cable should not be installed in 3/8″ flexible metal conduit due to the effects of capacitance. High-voltage GTO cable cannot be paired in the same conduit or be run more than 20 feet off the output terminals of the transformer in metal conduit.

Besides these issues, one should understand the impact of Section 600-23(b), Secondary-Circuit Ground-Fault Protection, or its exceptions regarding transformers. This information is paramount for the well being and safety of persons and property. These transformers provide a level of ground-fault protection for the secondary circuit wiring. Included in the secondary wiring circuit is the point of transition from code wiring methods to connections at the electrodes and tubing. One should also understand the aspects of Section 600-42(f)&(g), which addresses wet locations and electrode enclosures, which will be the focus of this article.

Figure 1. The dotted white line represents the route of the border neon, but where do we mount our trannies? How do we design our glasswork?

Regarding electric-discharge outline lighting, which is used most frequently in the neon industry, one should ask whether one is "…familiar with the construction and operation of the equipment and the hazards involved,” or with the listed acceptable components as presented by the United States standards laboratories and the United States-based independent third party electrical safety testing laboratories.

Does familiarity with these things matter? If staples are becoming a "now and again method” of installing high-voltage neon cable all over a pine or cedar wet-location commercial site, these violations of the NEC and the unsafe conditions they present should be addressed.

Electrode enclosures in wet locations

Photo 1. When dealing with exposed high voltage wiring in a "wet" location, it is imperative to adhere to space and listed "wet" location components. Exp. 3-1/2" glass "standoffs" with glass "wet orientated" electrode enclosures.

In many parts of the country, exposed wet-location neon and argon/mercury tubing are often the outline lighting system of choice. However, in the far north, even with cold-weather gases, long runs of glass are not practical in a -40°F outdoor environment. With high average snowfall, the resulting snow pack on a building’s roof can pull down glass as easily as it can shingles. Therefore, most neon tubing installations tend to be channeled with clear faces and listed per a third party independent electrical safety testing agency prior to acceptance by the authority having jurisdiction.

Climatic differences can have an impact on electrical installations in areas where the winter temperature tends to be only as cold as an early fall day in Vermont. Needs and parameters may change with the conditions. The interpretation of the Code for exposed border neon rests on NEC Article 600-3(a), Listing, applied in conjunction with Chapter 6 Part B, 600-30, Field Installed Skeleton Tubing.

Photo 2. In comparison, this border and lettering display exhibits virtually every code violation possible. Total absence of grounding or bonding; inadequate spacing; illegal "wet" location electrode enclosures, etc.

These sections of the Code were recently revisited during a prototype installation for a restaurant chain in the southeast part of the country. This site, besides having listed neon displays, called for 324 feet of 15-mm white, wet-location border tubing. After reviewing the specs and corporate signage standards that had been written in 1997 (and revised in October 1998), it was realized that some of the issues described no longer met the letter of the ’99 NEC or that current listing standards had become a concern.

Another problem was that various distributors in the locale did not carry many of the items needed to meet the minimum NEC requirements. The best approach at attaining compliance and safety the first time appeared to be teaming up with transformer and component manufacturers for help. Through the efforts of the authority having jurisdiction (electrical inspector), manufacturers, and other valuable industry resources, many issues were discussed, evaluated, and resolved. Communication certainly is a key component for success. [See photos 1 through 4]

Focusing on the entire secondary circuit

Electrode enclosures [Section 600-42(g)], spacing, and secondary-circuit ground-fault protected or isolated transformers [Section 600-23(b)] were the main areas of concern with this project, as they are with most neon installations of this type.

First, there are currently no listed "wet location” rubber or polymeric electrode enclosures (boots) per our United States based Nationally Recognized Testing Laboratories (NRTLs). The only listed organic products allowable in a wet location, and required for this project, were the polymeric electrode receptacle covers for our two metal electrode housings. Also, it should be understood that polymeric or plastic sleeving could not be used as a stand-alone wiring method for these high voltage secondary circuits. Therefore, in the consensus of all parties involved, the majority of the design had to be based on listed wet-location glass electrode enclosures and listed wet-location glass conduit plug assemblies.

Photo 3. Code violation alert. This is no way to wire in a secondary high voltage system. One shall not take high voltage cable and use "soda" hose as a wiring method. Only listed "wet" location conduit with proper conduit connectors is allowable.

The next area of concern was the fact that 324 feet of this border tubing was to be mounted on dry, stained and painted cedar, with roof flashing and metal capping appearing at various points along the route. In any electrical installation, space is usually an issue. However, in the world of high-voltage discharge lighting (neon/argon) where capacitance is an ever-present concern, routing and length of the secondary conductors needs to be addressed carefully.

The neon industry produces a 3½” long glass tube support, which, in the case of border tubing, is a minimum acceptable length for this type of installation. This minimum exists because the required clearances cannot be maintained when utilizing the standard 1–3/4-inch tube supports at a neon double-back. (Note: A neon double-back is a glass/electrode design in which the electrode is bent and brought up behind the visual length of the glass.)

The last issue under this scope has to be the wireway layout and the design of the transformer secondary circuit conductors. There is an aspect of long lengths of outline/electric neon discharge lighting that must be understood for achieving a safe installation. At the restaurant neon installation site, the average length of border glass that one of the many transformers supplied was around 60 feet. By conventional (series) wiring, we would have 30 feet of GTO wire running inside of 30 feet of metallic conduit out to each end of that section, which would be in violation of the Code. However, more importantly, even the compliant 20 feet used in this manner could be very destructive to both higher voltage 30 mA transformers and to the HV system being supplied by such transformers.

Photo 4. Code violation alert. Without the proper spacing and listed "wet" location electrode enclosures some installations are sure to cause problems--as indicated by the charring behind the rubber boots.

The neon industry and its transformer manufacturers have advocated alternative methods of wiring these runs of glass tubing. The methods applied are called "midpoint” and "virtual mid-point” wiring. This practice minimizes the length of GTO in conduit between the neon transformer HV outputs and the closest pair of electrodes to be energized. In reality it could take a 17- to 20-foot run of energized high-voltage cable in metallic conduit and reduce those runs to 6 inches. This topic, however, is an article by itself.

A prudent avenue to follow in regard to border/electric-discharge outline lighting may be to have this border tubing fabricated in listed (channelized) fixtures and then wired in accordance with Chapter 3 of the NEC.

Need for training

Perhaps the most common challenge is the need for training in Article 600, Electric Signs and Outline Lighting. To say that the neon industry needs training in the rudimentary aspects of commercial electrical wiring practices would not be an understatement. This training should not just be about box fill calculations or ampacity tables; it should also be about grounding and bonding, twisting off of conductors, bending pipe and other rudimentary jobs. Many contractors and installers in the neon industry have received little electrical trade training and, consequently, do not fully understand Article 600 of the NEC and many, unfortunately, are not aware of the existence of the Code. On the other hand, many electrical inspectors have received little neon trade training. Too often, this lack of training in the proper procedures of electrical wiring when it comes to the installation and inspection of neon, that special light source that adorns most commercial structures, could inadvertently lead to fires, ranging from the minor to the serious.

Final thoughts on education

Communication and education are the two main ingredients for safe and code-compliant neon installations. If one feels he is not qualified or is in need of improving knowledge and understanding in Article 600—one of the most misunderstood sections of the Code—the following symposiums offer a chance to turn a weakness into the strength it should be.

Those involved in the industry should be encouraged to attend one of the four symposiums scheduled for this year: January (Fort Worth); mid-February (Normal, IL); June (Columbus, OH); August (Anaheim, CA). These symposiums are either free or charge a nominal fee to the life safety community.

Then there is testing and education on new products that come to market. Since moving the corporation from Vermont to the foothills of western North Carolina, we have encountered opportunities and situations that shaped the foundation of this article. In conjunction with the issues discussed above, four of the major ferro magnetic manufacturers afforded us the opportunity to install a variety of new required 600-23 ’96 & ’99 code-compliant (UL 2161) power supplies. These transformers, which in most cases were just coming off the production lines, did not demonstrate any of the problems that were prophesied, such as nuisance (false) tripping or unreliability.

If we focus on education instead of our differences and band together the neon industry, electrical inspectors, and manufacturers for the common purpose of life safety, we will all have made a giant stride forward.

This article has been passed for review before publishing to various state and provincial electrical inspectors, manufacturers, electrical safety associations, corporate/industrial safety officers and the INA "”Codes and Installation Forum.”" Special thanks to: Les Beros, Sask Power, Regina, Saskatchewan; Regan Dickinson: Sign Business Magazine, Broomfield, CO; Telford Dorr, Microtron, Encinitas, CA; Jeff Hinkle, City of Hickory Code Enforcement, Hickory, NC; Kathryn Ingley: IAEI, Richardson, TX; Mike Johnston: IAEI, Richardson, TX; Al Smith, France Transformers, Fairview, TN

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Back to Basics: Grounding and Bonding as it Relates to Signs and Neon Installations

Posted By Michael Johnston, Saturday, January 01, 2000
Updated: Monday, February 11, 2013

Some features of electrical circuits and electrical systems are so fundamental they have appeared in some form in every edition of the National Electrical Code. These include insulation for wire type conductors, conductor (wire) sizing, and overcurrent protection for circuits (fuses or circuit breakers). Another long-time electrical safety requirement is grounding of electrical systems and equipment for safety. The grounding of metal electrical equipment and metal enclosures has been practiced in some quarters since the use of electricity began. This article will focus on grounding and bonding requirements as they relate to metal parts and metal equipment of electric signs and neon installations.

Figure 1. The term "grounded" is defined in the NEC in Article 100


The term "grounded” is defined in the NEC in Article 100 as, "Connected to earth or to some conducting body that serves in place of the earth.” The earth as a conductor is assumed to have a voltage potential of zero. Conducting bodies that serve in place of the earth can include, but are not limited to, conduit, metal enclosures, transformer cases, raceways, etc. Basically when metal equipment is grounded it is connected to the earth. (See Figure 1).

Figure 2. Grounding or earthing metal electrical enclosures puts both the earth and the metal enclosure at the same potential (voltage).

This can be accomplished in a few different ways. A metal object such as a box or other equipment enclosure that is grounded by connecting (bonding) it to the earth by means of an equipment grounding conductor to a grounding electrode conductor and, finally, to the grounding electrode (the conducting element connection to earth) of the system is thereby forced theoretically to take on the same zero potential as the earth. Grounding or earthing metal electrical enclosures puts both the earth and the metal enclosure at the same potential (voltage). (See Figure 2).

Figure 3. When a grounding conductor (could be a wire, conduit, or raceway) is broken, is inadequate in size, is not connected or has a poor connection, a hazardous, above-ground potential on the metal object may be present, creating a shock and fire haza

Any attempt to raise or lower the potential (voltage) of the grounded objects results in the passing of current (amps) over the grounding path until the potential (voltage) of the objects and the potential (voltage) of the earth (zero) are equalized. Usually, this above-ground potential is caused by a line- (hot conductor) to- ground fault. With both the metal enclosures and earth at the same potential (electrically), shock hazards are reduced and an electrically conductive path for any fault current to flow is established. When a grounding conductor (could be a wire, conduit, or raceway) is broken, is inadequate in size, is not connected or has a poor connection, a hazardous, above-ground potential on the metal object may be present, creating a shock and fire hazard. (See Figures 3 ,4 and 4a).

Grounding Electrical Systems and Equipment

Figure 4. When a grounding conductor (could be a wire, conduit, or raceway) is broken, is inadequate in size, is not connected or has a poor connection, a hazardous, above-ground potential on the metal object may be present, creating a shock and fire haza

The grounding of an electrical system and equipment is usually accomplished at the electrical service equipment of a building or structure. The grounded conductor (usually the neutral or white conductor) and metal enclosure of the electrical service are connected to the earth by using a grounding electrode conductor which connects to a grounding electrode system. [See figure 5]

Once this system and metal enclosures are grounded, the power is then distributed to the electrical panels with feeder conductors (the larger conductors supplying power to the electrical panel) that include an equipment grounding conductor, and finally to the branch circuit conductors (the conductors between the final fuse or circuit breaker in the electrical panel and the electric sign or neon transformer enclosure), which include an equipment grounding conductor for grounding the non-current-carrying metal parts of electrical equipment. These equipment grounding conductors are the extension of the grounding circuit, and as a result, are the conducting body that serves in place of the earth. (See Figure 6)

Figure 4a. When a grounding conductor (could be a wire, conduit, or raceway) is broken, is inadequate in size, is not connected or has a poor connection, a hazardous, above-ground potential on the metal object may be present, creating a shock and fire haz

Bonding of Electrical Enclosures and Metal Parts

Bonding of electrical equipment and enclosures simply means that the enclosures will be connected together in an appropriate manner to ensure electrical continuity and to ensure the capacity to conduct safely any fault current likely to be imposed on those enclosures. When a metal conduit is connected to a metal electrical junction box with a proper conduit connector or proper fittings, the two parts become one electrically because they are bonded together. (See Figure 7)

It is important that all connections and metal continuity be installed and maintained wrench tight. Wrench tight is a workmanship issue. The pride of workmanship must be held in high regard to comply with the rules and safety aspects of electrical installations contemplated by the NEC. It is important that care be taken to tighten locknuts and setscrews of all fittings as they enter electrical enclosures (i.e. junction boxes, timeclocks, electrical panels, transformer boxes, etc.). Loose connections can lead to arcing conditions when conduit or equipment grounding circuits are called upon to carry fault current. Loose connections can also lead to isolated metal equipment and enclosures, which become a silent and sometimes lethal shock hazard when energized.

Figure 5. Purpose of equipment Grounding Conductor

The Scope and Purpose of Grounding

The scope of grounding and bonding and the general requirements of grounding and bonding are contained in Section 250-2 of the National Electrical Code. These requirements include:

• Grounding of electrical systems,

• Grounding of electrical equipment,

• Bonding of electrically conductive materials and other materials, and

• Performance of the fault-current path.

Using the National Electrical Code

Figure 6. These equipment grounding conductors are the extension of the grounding circuit, and as a result, are the conducting body that serves in place of the earth.

The Code requirements for electric signs and neon installations are found in Chapter 6, Special Equipment, and specifically in Article 600 of the NEC. Grounding and bonding requirements for electric signs and neon installations are outlined in Sections 600-7 and 600-32. It should be pointed out that all of the Code rules in Article 250 are applicable to signs and neon installations unless the rules in Article 600 modify or amend those general requirements.

Section 90-3 of the NEC explains the basic arrangement of the Code. Chapters 1 through 4 apply generally, except as amended by Chapters 5, 6, and 7 for the particular conditions. The NEC contains the minimum requirements for electrical installations that are essentially safe, thus one must do at least that much. The main purpose of the NEC is the protection of persons and property from the hazards that arise from the use of electricity.

Figure 7. When a metal conduit is connected to a metal electrical junction box with a proper conduit connector or proper fittings, the two parts become one electrically because they are bonded together.

Back to Basics—The Path for Normal Current and Ground Fault Current

It is important to have a basic understanding of the paths for electrical current. For electrical current to flow properly it must have an adequate path. In the normal electrical circuit, current will seek out the source, taking any and all paths to try to return to that source.

In order for an electrical circuit to work properly, the circuit must be complete.

Figure 8.

In other words, for electrical current to flow in the circuit to an electric sign, the common 120-volt circuit usually will contain an ungrounded conductor (hot) and a grounded conductor (neutral). When properly connected, normal current will flow in this circuit. (See Figure 8)

The other type of current one must be familiar with is fault current, which will also follow all paths available to it to try to return to the source. Fault current in most cases is an abnormal or accidental situation. It is important that a proper path for fault current, in the form of a conductor, be provided with the circuit for safety. This conductor is referred to as the equipment grounding conductor of the circuit. With all metal parts and enclosure associated with the sign or neon installation effectively bonded together and connected to an equipment grounding conductor, two basic but important things are accomplished. First, the metal enclosures and parts are essentially put at the same electrical potential (voltage). Second, if a ground fault should occur in the circuit, an effective path is provided back to the source and to ground which ensures overcurrent device operation.

Figure 9.

The equipment grounding conductor and proper bonding are essential elements for safety in electrical signs and neon installations. This safety component of the circuit acts as the silent servant waiting to perform its ever-important function.

The high voltage secondary circuits (GTO in a wiring method that extends from the transformer to the discharge tubing) for neon installations also introduce another electrical component into the electrical circuit. This component is called capacitance. Capacitance coupling can actually raise the potential (voltage) on ungrounded metal equipment and metal parts. Proper grounding and bonding of metal enclosures and associated metal parts ensure that these parts remain at earth potential. Other electrical resource material on electrical theory is available that expands on this term.

Figure 10.

Electrical installations for sign circuits and neon installations are not exempt from these basic safety requirements. Transformers installed and wired using the balanced mid-point reference wiring method require the secondary output conductors to be as short as possible, and the secondary return leads must terminate on a mid-point grounding connection terminal provided for that purpose by the transformer manufacturer.

Proper grounding and bonding connections of the entire branch circuit wiring methods and secondary circuit wiring methods are critical for proper operation and safety of these secondary circuits wired by this mid-point reference method. Mid-point reference wiring methods are just mentioned in this writing and will be expanded upon in further writings.

The Sign and Neon Branch Circuit Wiring Methods

Figure 11.

All conductors of the branch circuit supplying power to a sign or primary (line side, usually 120-volt input) of a neon transformer are required to be installed in the same raceway, cable, trench, wiring gutter, unless permitted otherwise by the NEC. This includes all conductors (wires) of the circuit, including the equipment grounding conductor, which can be in many forms. It can be in the form of a conductor, conduit, tubing, cable armor, or combination of cable armor and conductor. (See Section 250-118 of the NEC).

Figure 11a.

In Article 600 of the NEC, there are requirements for branch circuits supplying signs and outline lighting systems. The wiring method (cable, conduit or raceway) used to supply signs and outline lighting systems must terminate within the sign, outline lighting system enclosure, junction box, or a conduit body. This circuit that terminates at the sign or neon transformer or power supply enclosure contains the equipment grounding conductor for the circuit. This conductor should be terminated to the metal enclosure. (See Figure 9)

This termination should be made by use of approved means. Sheet metal screws (tek screws) are not acceptable for attachment of equipment grounding conductors per the NEC. (See Section 250-8). Proper grounding clips, screws, or lug type terminations are available for this purpose.

This termination of the equipment grounding conductor establishes the connection to ground for those enclosures and puts them at the same zero voltage potential as the earth. Section 600-7 of the NEC requires signs and metal equipment of outline lighting systems to be grounded. The Code also allows for listed flexible metal conduit or listed liquidtight flexible metal conduit (per Article 351 of the NEC) to be used as a bonding means in lengths not exceeding 100 feet. (See Figures 10 and 11) One should keep in mind that there is a length limitation on secondary GTO conductors of 20 feet when installed in metallic wiring methods and 50 feet when installed in nonmetallic wiring methods. See Section 600-32(j).

Figure 12.

Small associated metal parts not exceeding 2 inches in any dimension, and not likely to become energized (such as the metal mounting means for tubing supports), and spaced at least ¾ inch from the neon tubing are not required to be bonded. Where listed liquidtight nonmetallic conduit is used for installing the secondary high voltage GTO conductors from the transformer or power supply to the neon tubing and where there are associated metal parts that require bonding, a bonding conductor is required to be installed. (See Figure 11a) This bonding conductor is required to be installed separate and remotely spaced from the nonmetallic conduit. It should be pointed out here that this wiring method is not electrical nonmetallic tubing, which was deleted from the 1999 NEC as an acceptable wiring method for GTO secondary conductors. See Section 600-32 of the NEC. The wiring method referred to here is rigid nonmetallic conduit.

Figure 13

A spacing of 1½ inches is required to be maintained when the secondary circuit operates at 100 Hz or less. When the secondary circuit operates at over 100 Hz, the spacing requirement increases to 1¾ inches. (See Figures 12 and 13). This conductor is required to be not smaller than No. 14. Metal parts of a building or structure are not permitted to be used as a grounded or equipment grounding conductor.


Proper grounding and bonding is a basic requirement in the NEC and is found in Chapter 2, which is appropriately titled, "Wiring and Protection.” The minimum Code requirements are set forth to protect persons and property from the hazards that arise from the ever-expanding use of electricity. Following these basic minimum requirements for grounding and bonding of signs and neon lighting installations contributes to the safe use of electricity.

The Code requirements in this writing are based on the 1999 edition of the National Electrical Code. Always consult the local authority having jurisdiction if in doubt as to the NEC requirements or any local amendments or requirements.

This article is being published in the January 2000 issue of Sign Business Magazine.

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Check and Be Sure of GFCI Safety Protection

Posted By NEMA, Saturday, January 01, 2000
Updated: Monday, February 11, 2013

"A safety revolution is underway in the electrical wiring of buildings,” writes Earl Roberts in his book Overcurrents and Undercurrents.1 He is writing about the use of electronics in circuit protection and specifically in the ground-fault circuit interrupter (GFCI). Just as electronics have enhanced the world of consumer appliances and communication, the use of electronics in the GFCI has resulted in a significant improvement in the safety of electrical systems.

Proven GFCI Safety Record

Notice Roberts’ use of the word "safety” as being under revolution. The GFCI indeed revolutionized the safety of electrical systems. Its purpose is to protect people from electrical shock or electrocution. It first appeared in the 1968 edition of the National Electrical Code (NEC) in Section 680-4 to protect underwater lighting of swimming pools. The successful use of GFCIs in providing electrical shock protection has resulted in continued expansion of GFCI requirements in successive editions of the NEC. Its application under the NEC has grown such that in the 1999 edition it is required in specified locations in kitchens, bathrooms, garages, unfinished basements, pools, fountains, rooftop receptacles, construction sites and elsewhere. Confirmation of the GFCI’s contribution to safety is seen in the reduction in electrocutions since the GFCI’s introduction. Whereas in 1975 there were 650 reported deaths related to consumer products, in 1996, there were 190—less than one-third of those in 1975. This information comes from the Consumer Product Safety Commission. Many of the lives saved can be attributed to GFCI protection.

Useful Service Life

As with any electronic device, the GFCI will eventually reach the end of useful service. Think about a TV set that has finally reached the end of its useful performance. The picture or sound that had once been clear and enjoyable is no longer so. In fact, the unit may simply be "dead.” We have to replace it if we wish to continue receiving our programs. The end of life for other electronic devices, however, may not be immediately evident to the consumer. For safety related devices, it is therefore essential that, if test features are integral in the design, the consumer has the discipline to use those features.

Although GFCIs have proven to be dependable products with a long service life, they must be replaced if their useful service life has expired. They are providing valuable protection that should be maintained. Replacement is also required to maintain compliance with the NEC. To help know when to replace them, manufacturers provide a test button feature available to every user. The instructions provided with or marked on every GFCI unit tell the consumer to test the unit monthly. The test-button feature and standardized instructions are an industry wide requirement of UL 943, Underwriters Laboratories Standard for Safety for Ground-Fault Circuit Interrupters.

The push-button test is simple for anyone to perform: push a button and confirm that the unit trips. Each GFCI has a test button that can be pressed to give a visual indication that the protective electronics in the GFCI are operating. The button is marked "TEST”on both circuit breaker and receptacle type GFCI’s. When this test button is pressed either the circuit breaker handle will move to the trip position or the "RESET” button on the receptacle type GFCI will pop out. There will also be an accompanying audible click. If the GFCI is working correctly, all power to downstream outlets will be disconnected when the test button is pushed. Power will be restored when the "RESET” button is pressed on the receptacle GFCI or the circuit breaker handle is reset.

If there is no tripping indication, the unit is no longer functioning as intended and must be replaced. The GFCI will still permit electrical current to flow if it is kept in service, but the electronic circuitry will no longer provide protection. The person doing the testing must respond to the test. A GFCI is not like the TV that is no longer useful when it stops functioning. The GFCI is designed to continue to permit current to flow, as if it were a standard receptacle or circuit breaker, to supply power until the device can be replaced.

Field Status Questioned

The November/December 1999 IAEI News carried an article titled, "Are All Those GFCIs Out There Working?” The survey cited in the article draws attention to the possibility that a percentage of GFCIs are no longer operational and then concludes that a feature developed by the company employing the author be adopted for all GFCIs as a solution. The issue of potentially non-operational units deserves careful investigation.

The survey information presented in the article was first communicated to manufacturers of GFCIs in August 1999. NEMA member companies have begun an evaluation of the facts. NEMA manufacturers have no information that supports the level of non-functionality indicated by the information presented in the article. Several manufacturers have reviewed their records and conducted informal surveys that seem to contradict the information contained in the article.

As we review the information in the article, we find that the survey failed to take into consideration the method used to test the GFCI, the age of the home, the age of the GFCI and the cause and mode of GFCI non-functionality. A number of items from this early information need to be better understood before the information can be used constructively by GFCI manufacturers or by standards developers for the purpose of revising product standards.

In order to establish the facts scientifically, NEMA members are initiating a study of the state of GFCI units in the field to be completed in 2000. To accomplish the study, training is being provided to those performing the checks, a specific test protocol has been established, and non-operational units will be collected and examined for cause. Age and condition of any non-operational units will be recorded. UL has been supportive of the NEMA study and UL will coordinate documentation of information collected. The intent is to learn if units are non-operational and, if so, to determine the cause and percentage of non-operational units.

Product and standard improvements over the years have already dealt with many potential causes of GFCI failure such as lightning, environmental conditions and incorrect installation. Products produced before these improvements were made may expire earlier than newer products. One value of a study such as the one NEMA is initiating is that the cause of non-operation can be learned and addressed. Date of manufacture will also be learned for any products that have expired. Until the causes of non-operation are known and the level of non-operation has been verified, improvements cannot be identified, if any are needed.

It should be clarified that GFCI test functions are performing as intended, to the best knowledge of manufacturers. The test button feature provided correctly indicates products that have expired and must be replaced. It may be found that residents are not checking units and replacing those that are non-operational. Although manufacturers have taken steps to improve reliability and surely will continue to do so, residents must do their part in checking their units and replacing any that have expired. Some units have been in use for over 25 years.


The solid protection brought to the use of electricity by the GFCI is a matter of record. It is a record that endorses the early work of Professor Charles Dalziel who helped define what protection is and introduced the first GFCIs. It also endorses the advent of electronics that permits the protection to be widely available. The industry is committed to knowing the status of GFCI products in the field. To retain the solid protection that is already available, residents must include periodic checks of their GFCIs just as they do for fire alarms to be sure that safety equipment is operating properly.

1Earl W. Roberts, Overcurrents and Undercurrents, Mystic Publications, Mystic, CT, 1996.

About NEMA: NEMA is the trade association of choice for the electrical manufacturing industry. Founded in 1926 and headquartered near Washington, D.C., its approximately 450 member companies manufacture products used in the generation, transmission and distribution, control, and end-use of electricity.

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Modifications Affect UL Listing

Posted By Underwriters Laboratories, Saturday, January 01, 2000
Updated: Monday, February 11, 2013

Question: Listed product modification

Can a UL Listed product be modified in the field if the manufacturer indicates that the revision is ok and sends out new parts?


The UL Mark applies to products as they were originally manufactured. UL does not know the effect modifications in the field will have on a product. Therefore, unless the modifications are specifically tested and evaluated by UL, UL cannot say that the modifications void the UL Mark, or that the product continues to comply with UL’s safety
requirements. The exception would be when the product has specific replacement markings.

Question: Listed product

How can I confirm if a product is UL Listed?


Only products that bear the UL Listing Mark are considered UL Listed. If you would like to verify a Listing, UL offers direct access to search UL’s Online Certification Directory Database A search can be conducted by using a number of parameters using the information provided on the UL Mark and the product nameplate. This search may include the UL file number, product identity, the manufacturer’s name and the model number of the product.

You may also be able to verify the Listing by referencing the published UL directories. If you do not have access to the internet or UL’s printed directories, you can contact a UL
Regulatory Services Representative.

Question: Harmonized UL standards

Currently there are approximately 93 bi-national or IEC harmonized UL standards. Since European and other countries have different utility service voltages and frequencies, how has harmonization affected the safety relating to installation and use of equipment?


UL Standards for Safety are developed to be compatible with the National Electrical Code (NEC®) installation requirements. Harmonized UL Standards maintain this compatibility. Standards that have been harmonized with IEC documents include appendices addressing specific installation requirements for various countries.

Question: Safety smarkings

Does UL require manufacturers to place required safety markings in a readily visible location on electrical equipment, such as air-conditioning units, electric signs, and luminaires?


UL Standards for Safety require safety markings to be located in a readily visible location after installation. Tools are not to be required to disassemble the product to view the safety markings. In addition, the UL Listing Mark is to be located such that it is visible without the use of a tool.

For some products, such as wire connectors, the UL Mark is on the smallest unit container. This is due to the size or shape of the product, which physically would not permit the UL Mark on the product itself.

Question: Installation instructions

Are the installation instructions part of the UL Listing? Are all Listed products required to have installation instructions? Are installation instructions reviewed by UL?


Installation instructions are considered to be a part of the UL Listing.

The UL Standards for Safety used to investigate products contain specific requirements regarding the content and appearance of the instructions. Installation instructions are not required to be marked with the UL Mark, but they are required to be provided with the product bearing the UL Mark. Some products are not required to have installation instructions when the National Electrical Code contains all the necessary installation requirements, such as outlet boxes. UL staff reviews the instructions, both during the initial evaluation of the product, as well as during the continual Follow-Up Service at the factories. The clarity of the instructions is also reviewed.

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The Storage of Hazards

Posted By David Young, Saturday, January 01, 2000
Updated: Monday, February 11, 2013

The excess space inside electrical supply stations (substations) is often considered for storage of construction materials.

The National Electrical Safety Code® (NESC®) in Rule 110B2 prohibits storage inside an electrical supply station even when stored well away from the energized conductors and equipment. The only exception is the storage of minor parts essential to the maintenance of the installed equipment, i.e., fuses, switch handles. The rule does not prohibit the expansion or maintenance within the supply station. Construction materials associated with the expansion/maintenance may be stored within the supply station during the construction period provided qualified personnel do the work and all clearance requirements are met while work is being performed. Qualified personnel are people with adequate knowledge of the installation, construction and operation of apparatus and the associated hazards. The intent of Rule 110 is to keep unqualified people out of supply stations. You may recall from my November/December 1997 IAEI article, "A Substation is Not Just a Fence,” a supply station can be a very hazardous place to unqualified personnel because the NESC® electrical clearance requirements inside the supply station are considerably less than that required for areas accessible to the general public.

Storage inside a supply station invites unqualified personnel into the supply station. The stores or delivery personnel delivering material to the supply station may not be qualified to enter and unload materials in a supply station. The construction personnel who enter the supply station to pick up the materials may not be qualified to enter and load materials in a supply station. Storage of materials attracts would-be thieves into the supply station.

When space permits, an interior fence or other barrier can be installed to partition off the storage area from the electric supply equipment space. The interior fence or barrier must meet the requirements of Rule 110A (height, signage and safety clearance zone) and grounded in accordance with Rule 92E. Entrances to the storage area should be located so that personnel dealing with the storage do not have to pass through the supply equipment space. If a chain link fence is used around the storage area in lieu of a solid barrier, I recommend suitable visual barrier webbing be laced into the fence fabric to limit the attraction to would-be thieves.

If you have general questions about the NESC, please call me at 302-454-4910 or e-mail me

National Electrical Safety Code and NESC are registered trademarks of the Institute of Electrical and Electronics Engineers.

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Comments on GFCI Article/IAEI Bonus Points Program

Posted By Philip Cox, Saturday, January 01, 2000
Updated: Monday, February 11, 2013

An article entitled "Are All Those GFCIs Out There Working?” was printed on pages 66-68 of the November/December 1999 issue of the IAEI News. The printing of that article was in error and I wish to extend an apology to readers of the IAEI News and other interested parties for the premature release of that article. The material was submitted to the IAEI for consideration and a working copy was reviewed. I declined to authorize the printing of the material and that information was relayed to the submitter. Apparently a copy of the submitted article was processed for publication with the assumption that it had been approved. It is apparent that we will have to do a better job of controlling the process of developing and producing IAEI publications. Specific guidelines are currently being developed to help avoid such incidents in the future.

The article raised questions as to whether or not GFCIs in existing installations are working properly. The IAEI is interested in obtaining reliable information regarding the safe installation and use of electrical equipment and products. Should evidence be found that GFCIs or other electrical equipment are not performing correctly, that information would be of interest to inspectors and other IAEI members. Such information could be used in a very productive way to improve product standards and to develop appropriate electrical safety rules. While it is evident from the article that considerable effort had been made to obtain data from the field regarding incidents of failures, it appears that additional information needs to be gathered and evaluated before any conclusion is reached that will affect code rules or installation procedures. A study conducted under strict research guidelines that includes gathering of data on GFCI installations and testing those units that do not function correctly to determine the cause can provide valuable information for the industry.

I understand that the National Electrical Manufacturers Association (NEMA) is planning to initiate a research program that will involve a study of GFCI installations and performance. A thorough study of this issue should provide answers to many questions raised as to how GFCIs perform over time. There appears to be interest in determining if reported incidents of GFCIs not working properly are actual equipment failures or due to other causes. Evaluation of devices that have failed in the field can result in a better idea of what caused the equipment to fail.

Lightning damage is indicated in the published article as one potential cause of GFCI failure. It is widely recognized that energy released through lightning strikes can cause damage to electrical equipment as well as to property in general. It would be beneficial to find out more about the significance of damage to GFCIs and other electrical equipment caused by lighting and the NEMA study should be able to answer many questions as to the impact lightning has on GFCI equipment and operation.

Many items printed in the IAEI News generate discussions and result in different opinions by readers. The stimulation of discussion is generally productive. It is hoped that the inadvertent printing of the article on GFCIs in the November/December issue of the IAEI News will have a positive effect by generating good discussion of the matter and result in an appropriate solution to any problem that may exist. For additional information on this subject, see the article by the NEMA Ground Fault Personnel Protection Section on pages 38-39 in this magazine.

IAEI Bonus Points Program

The IAEI tries hard to find ways to appropriately recognize members who demonstrate their continued support of the organization and its objectives over the years. These individuals are the ones who help make the IAEI strong through their participation in organizational activities in promoting the electrical safety system that benefits the public. An IAEI policy implemented several years ago provided a complimentary copy of the National Electrical Code to members who requested it. That policy was amended to include certain IAEI-developed publications with the intent to provide a variety of publications in addition to the NEC. It is commonly known as the bonus points program and includes the provision that points accrue each time membership is renewed on a consecutive basis with a limit on the maximum number of points permitted to be accumulated. It should be noted that including the NEC as part of the program would not be possible without the cooperation and support of the National Fire Protection Association. Including IAEI-developed publications in the program has added a significant financial load. It was made possible only because costs were kept to a minimum by the way material was developed and by the type of books produced. When the IAEI began producing books with much more extensive material and in four color, the cost of production changed dramatically.

It is the intent that the IAEI continue to improve on its publications, both in content and in appearance. According to comments received, this appears to be what IAEI members want. The objective is to have the best educational material available and to present it in a fashion that is technically accurate, easy to understand, and enjoyable to study. The down side of this is that producing material of this quality is extremely expensive and affects the ability of the IAEI to provide the publications as an option in the bonus points program.

The IAEI Board of Directors reviewed the bonus points program during the November 1999 annual meeting and determined that it needs to be adjusted. It was concluded that the plan should be similar to what it was before where only the soft cover edition of the NEC is provided. In order to provide a reasonable time during transition to the revised program, members who have the required three (3) annual renewal points (bonus points) achieved through three consecutive years of renewal may exchange those points for either a soft cover 1999 NEC or one of the IAEI publications presently included in the program by December 31, 2000. Following that, IAEI publications will no longer be part of the bonus point program. Effective January 1, 2001, those individuals who qualify will be able to select the soft cover edition of the NEC while supplies are available.

Read more by Philip Cox

Tags:  Editorial  January-February 2000 

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How Hot is That Wire?

Posted By David Young, Monday, November 01, 1999
Updated: Wednesday, August 29, 2012

The conductor temperature is a critical part of the design, construction, and checking clearances of aerial electric supply lines.

Line Design

In my article on "Overhead Line Design From Scratch – Part 1″ in the March/April 1998 issue of IAEI News, I discussed conductor choice based upon steady-state ampacity, transient ampacity, short-time ampacity, voltage drop, sag/tension characteristics, cost and losses. The ampacity of the conductor is a function of the conductor’s physical properties, conductor maximum operating temperature and ambient weather conditions, including air temperature, wind velocity and solar intensity. For insulated conductors, the maximum operating temperature is the maximum temperature of the insulation material. For bare conductors, the maximum operating temperature is chosen by the designer of the aerial electric supply line.

How high can we go? Economics limit the conductor temperature well below the temperatures that can actually damage the conductor. As the conductor temperature increases, the sag increases. The sag increase requires us to use taller structures or more structures to maintain good clearances. Both increase the cost of the line. As the conductor temperature increases, the resistance of the wire increases. The resulting increase causes greater voltage drop and higher losses. If we set the maximum operating temperature too low, we end up using a much larger and more expensive conductor than necessary. 212° F. is commonly chosen. Once we choose a maximum operating temperature and design the line based upon that temperature, we must make sure the operating personnel do not allow the design ampacity to be exceeded.

An industrial plant manager once asked me the ampacity of the 12kV lines that feed the various buildings in the industrial complex. The lines had been designed and constructed by a consultant about twenty years before his request. There was no record of the ampacity/maximum operating temperature used to design the line. We measured the ground clearances and conductor sags for several of the longest spans. We also measured the conductor temperatures. We calculated the conductor tension and plugged it into a sag/tension computer program to determine sags at various high temperatures. Since we measured conductor heights above ground at the points of attachment on the structures, we calculated the maximum conductor sags, which would comply with the NESC® requirements. The plant manager was not happy to find out the line was constructed for a maximum operating temperature of 130° F. and that they were already exceeding the ampacity of the line. The line was in violation of the NESC® requirements. The line was probably field designed.

Line Construction

Once we decide what maximum operating temperature we will use to design the line, we then have to determine the stringing sag/tension we will use to construct the line. As discussed in my March/April 1998 article, we get the sag/tension stringing details from the sag/tension computer program. The temperatures listed by the program are conductor temperatures, not air temperature. On a hot sunny day, it is not uncommon for a conductor not carrying any current to be 50 degrees hotter than the air temperature. The line crew installing and tensioning the conductors must be given the sag/tension details from the computer program and must have an accurate way of measuring the conductor temperature at the time of tensioning. I give our construction personnel a graph of stringing sag in inches versus conductor temperature so they can pick off the appropriate sag for their conductor temperature.

Conductor Temperature Measurement

Hand-held electronic thermometers with surface probes work very well for measuring the temperature of "dead” conductors like during the stringing process. When we are checking the clearance of an existing energized line as discussed in my July/August and September/October 1999 articles, measuring the conductor temperature is much more difficult. The electronics of most thermocouple type electronic thermometers don’t like high voltage. The devices turn off when the energized wire is contacted. I understand that some thermistor-type electronic thermometers have the same problem. The device I use is a thermistor type and is no longer available. I’m working with two manufacturers to find a device that will work. When I find a production device that works, I will let you know. Most infrared thermometers don’t work because the target diameter is too large. For clearance measurement, we want to be able to measure the conductor temperature from the ground. The device I use is mounted on a "V” shaped guide on the end of a 50-foot fiberglass extension pole (the same pole I use to measure vertical clearances). The probe is mounted at the bottom of the "V” so that the probe doesn’t miss the conductor. An electronic thermometer with a "peak” function is necessary so that you can recall the conductor temperature after you lower the device to the ground.

The Alternative

As discussed in my March/April 1998 article; IEEE® Standard 738-1993 is one source that can be utilized to determine the ampacity of bare conductors. The calculation method presented in the standard and the associated computer program (included with the standard) can also be used to predict the conductor temperature given the conductor’s physical properties, current flow in the conductor and weather conditions. The results are only as accurate as the input data. The input data consists of thirteen variables, which are not easy to measure.

1. Air temperature

2. Wind speed

3. Angle between the wind direction and the conductor

4. Altitude of the conductor above sea level

5. Direction of the conductor relative to a compass

6. Latitude of the conductor

7. Sun time

8. Visibility

9. Conductor diameter

10. Conductor resistance at 25° and 75° C.

11. Conductor emissivity

12. Conductor absorptivity

13. Current flow in the conductor

Each of the variables is explained in detail in the standard. To complicate matters, each variable is considered by the program to be constant. The field conditions are not constant. Variations in air temperature, wind speed, wind direction, visibility and current flow all affect the results. For that reason, the program can only be used to roughly predict the conductor temperature.


There is no substitute for actual measurement of the conductor temperature.

If you have enjoyed this article or have general questions about the NESC®, please call me at 302-454-4910 or e-mail me at

National Electrical Safety Code®, NESC® and IEEE® are registered trademarks of the Institute of Electrical and Electronics Engineers.

Read more by David Young

Tags:  November-December 1999  Other Code 

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Is Everything in the Electrical Code?

Posted By Leslie Stoch, Monday, November 01, 1999
Updated: Wednesday, August 29, 2012

Most of the time, we tend to rely exclusively on the Canadian Electrical Code for information, and for the minimum requirements on building a safe electrical installation. But is the information contained between its covers enough for our purposes – or do we need to look further afield to find out more? Are there any other sources of information we should explore to grasp the complete picture?

Let’s consider one prime example where the electrical code does not give us all of the information we need to make a safe installation. Our example – a high voltage padmount transformer (over 750 volts primary voltage) must only be supplied from a grounded electrical distribution system that brings a primary neutral conductor into the substation. This is imperative in the event of a ground fault, since we want all of ground fault current to return to its source through a low impedance path. Hazardous step and touch potentials near the transformer can result when there is no neutral and when the ground fault return path is through the earth. We must provide the lowest possible impedance fault path to make sure that any faults in equipment or cabling are disconnected promptly by the upstream ground fault protection equipment.

You will recall that step voltage is the voltage between your feet when walking or standing near high voltage electrical equipment during a ground fault. Touch voltage is the voltage between your hands and your feet when you touch electrical equipment during a ground fault. Both are the result of ground current flow x the impedance of the current return path (Ohm’s Law).

Safety in a padmount transformer installation is surely most important, since we know that padmount transformers are not usually enclosed by fences and are often accessible to the public. We will not find this important bit of information in the Canadian Electrical Code – because it’s not there. But rather, we must turn to the CSA padmount transformer standards, CAN/CSA-C227.3-M91(R1997) for single-phase transformers or C227.4-M1978(R1994) for three-phase transformers to access this information. But you will find these requirements in the very first paragraph, the Scope paragraph in each standard, which describes the conditions of use for this type of equipment.

There are many more examples. As we peruse the Canadian Electrical Code, we find that not all of its requirements are to be found between it covers. There is an abundance of requirements and/or additional information necessary for doing a complete design or installation job. Here are a few more examples.

1. A footnote under Table 31 – Minimum Horizontal Separations of Line Conductors Attached to the Same Supporting Structure states: "For voltages greater than 69 kV and for spans greater than 50 m, the requirements of CSA Standard CAN/CSA-C22.3 No.1 shall apply.” Note the words shall apply. That means, of course, that when we design or build an overhead line to be used at above 69 kV phase-to-phase or any line when the pole spans are greater than 50 metres, the code does not have this information and we must turn to that standard for the requirements on clearances.

2. Rule 12-012(12) Underground Installations states: "For installations not covered by the foregoing requirements of this Rule, the requirement of CSA Standard C22.3 No.7, or the applicable standard, whichever is greater shall apply. That tells us, when the installation falls outside the scope of requirements covered by the electrical code, we must consult the appropriate CSA standard.

3. Rule 36-304(2) Station Ground Resistance refers us to Table 52 and Appendix B for information and data on the maximum permissible step and touch voltages in a high voltage substation. We must have this information to design the station ground grid in such a way that these values will not be exceeded. When we turn to Table 52 and Appendix B, we find that we must also have access to another standard, IEEE No. 80 Guide for Safety in Substation Grounding to find the formulae to perform these calculations. Fortunately, there are a number of available software programs based on the standard, to perform this arduous task more easily.

4. Fire pumps – Rules 32-200 to 32-212 provide the basic electrical code requirements for fire pumps. However, the code does not give us the complete information on overcurrent protection, etc. Therefore, Appendix B refers us to NFPA Standard No. 20 Standard for the Installation of Centrifugal Fire Pumps for the rest of the information.

These are only a few of many documents, which the Canadian Electrical Code refers us to for additional requirements or further information. Where can we find a list of these publications? Go to pages 32 to 34 in the 1998 Canadian Electrical Code. There you will find a list of the publications referenced in the rules as requirements or available for more information. At the bottom of the list you will also find a listing of the organizations that produced these publications.

As mentioned in previous articles, you should consult your local inspection authority for a more precise interpretation of any of the above, in each province or territory as applicable.

Read more by Leslie Stoch

Tags:  Canadian Code  November-December 1999 

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