Code questions presented in the Focus on the Code section of the IAEI Magazine. Search Blog

2013, May-June

What’s Happening to Table 310.15(B)(7)?
by John Stacey

In the 2011 NEC, does Table 310.15(B)(7) override any ampacity adjustment factors, such as temperature correction factors, or do any ampacity adjustment factors render Table 310.15(B)(7) noncompliant? Read more

Are there any provisions in the NEC that address the de-energizing of rooftop photovoltaic (PV) wiring in an emergency situation for first responder emergency personnel?
by James Rogers

Let’s begin with de-energizing. It is well understood that when electrical circuits and equipment are de-energized, they are disconnected from a source of power utilizing a disconnecting means. Using this analogy, your question could be rephrased to inquire if there is a requirement for a disconnecting means for PV circuits; that direct answer is yes. Read more

2013, March-April

Dry-Type Transformer, Grounding & Bonding Terminations
by Keith Lofland

Grounding and bonding termination points in dry-type transformers are seemingly an issue in that the NEC apparently is silent on where in a dry-type transformer grounding and bonding conductors should be landed (terminated). In addition, many times installers utilize poorly chosen termination means such as installing a lug over a vented portion of the bottom of the transformer. Are there such termination requirements in the NEC and if so, where are they located? Read more

Would the addition of the control circuit conductors in one conduit of this power circuit run in parallel be a violation of having the same number of conductors and the same electrical characteristics
by Jeff Sargent

A parallel conductor branch circuit is run from a switchboard to a 3-phase rooftop air-conditioning unit using two metric designator 63 (2½ in. trade size) conduits with four 4/0 AWG copper conductors (3-phase, 1 EGC) in each conduit. One of the conduits also contains six 10 AWG Class 1, 120-volt control circuit conductors. Would the addition of the control circuit conductors in one conduit of this power circuit run in parallel be a violation of having the same number of conductors and the same electrical characteristics in each conduit? Read more

2012, September-October

Is it code-compliant to install Type NM cable exposed in an attached residential garage? How about a detached garage?
by Charles Palmieri

Thank you for the inquiry. For clarity, I will frame my response. First, I will substitute the term residential with the term dwelling which is defined in NEC Article 100. Second, I will consider the attached garages or detached garages and storage sheds to be directly associated with one- and two-family dwellings. Third, all structures considered will be of Types III, IV, and V construction. Read more

We have some radio equipment that uses a screw-type fastener to bond or attach the grounding conductor to the antenna assembly. Can this screw be any ordinary screw, or does it need to be a "listed” screw meeting the requirements of 250.70 or, perhaps, 250.8?
by Tom Moore

We first need to point out that the term grounding conductor as referenced in the question and used in previous editions of the NEC has been revised to three more appropriate terms: grounding electrode conductor, bonding jumper, or bonding conductor. CMP-16 accepted these revisions throughout Article 770 and all Chapter 8 articles to provide consistency and correlation with defined grounding and bonding terms in Article 100, and to avoid the use of an undefined term in the communications articles. Read more

2012, May-June

Are there any other such receptacle replacement requirements?
by Keith Lofland

The GFCI requirement for replacement receptacles is located at 406.4(D)(3) in the 2011 NEC. An example of this would be at a non-GFCI protected kitchen countertop receptacle or a bathroom receptacle being replaced. Read more

Do washing machines require GFCI protection?
by Mark Hilbert

Thank you for your correspondence. There is no specific requirement in the NEC for the washing machine itself to have GFCI protection. Section 210.52(F) requires a receptacle outlet to be installed for the laundry area and it must be supplied by a 20-ampere branch circuit in accordance with 210.11(C)(2). Read more

2012, March-April

Bonding Copper Piping for a Hydromassage Tub
by Keith Lofland

All metal piping associated with a hydromassage bathtub and all grounded metal parts in contact with the circulating water is required be bonded together using an 8 AWG solid copper bonding jumper. Read more

Connecting IT Equipment
by Keith Lofland

First, we must assume that the information technology equipment in question does qualify as IT equipment by meeting all of the six conditions listed at 645.4. If the IT equipment in question does not meet all of the special conditions of 645.4, then this equipment would be subject to the provisions of Chapters 1 through 4 of the NEC. Read more

2012, January-February

When installing a supply-side bonding jumper, what are the requirements for installing such a conductor both inside and outside a raceway? What type of conductive material is suitable for a supply-side bonding jumper and how is it sized?
by David Williams

The term supply-side bonding jumper first appeared in the 2011 National Electrical Code as a result of a CMP-5 Task Group regarding the proposed revisions to Section 250.30 for grounding separately derived systems. Read more

Where branch-circuit conductors pass through a panelboard and do not originate or terminate in that panelboard, is there any requirement for identifying where the overcurrent devices are located for these pass-through conductors?
by Keith Lofland

In this instance, the panelboard is serving the function of a pull box for these pass-through conductors. A panelboard is permitted for this purpose if proper wire bending space is provided as per 408.55. Read more

2011, November-December

Both dc and ac photovoltaic systems in a common enclosure?
by James Rogers

Section 690.4 is the first section of the 2011 NEC that covers the installation raised in the first portion of your question. There seems to be one summation that is being made for clarity, the question inquires about "both dc and ac photovoltaic systems.” The summation being made deals with a common junction box where the PV output circuit conductors and the inverter output circuits are both present on an interactive system. Read more

Single receptacle for a refrigerator?
by Bill McGovern

A single or duplex receptacle is acceptable in this situation. Section 210.52 addresses the requirements for dwelling unit receptacle outlets. Part (B) of this section covers the requirements for receptacles installed in the kitchen and other associated areas that will serve portable appliances along with refrigeration equipment. Read more

2009, January-February

Protect grounding electrode conductor in crawl?
by Michael Johnston

You are correct in your understanding of this rule. The last sentence of 250.64(B) requires an 8 AWG copper grounding electrode conductor to be protected from physical damage by installing it in rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, electrical metallic tubing, or cable armor, and no exceptions to this requirement. Read more

Breakers not listed on panelboard data sheet
by Lanny McMahill

First, it is understandable that for older panelboards it is difficult to find new or replacement circuit breakers. Typically, the panelboard may be obsolete, the manufacturer may be out of business or perhaps purchased by another manufacturer. In addition, electrical equipment design and manufacturing technologies change. As a result, the equipment is not produced or there is little demand for such equipment. Read more

Exhaust Fans on Pitched Roofs
by Lanny McMahill

As you have noted, there is nothing in the National Electrical Code to preclude the installation of an exhaust fan on a roof — this is regardless of the roof being flat or pitched. Realistically, installing an exhaust fan on a roof is no different than if it were installed up high in an exterior building wall or down low in an underground vault. Read more

2008, September-October

Is an additional bare copper bonding wire jumper required?
by Michael Johnston

Your question deals with use of the grounded conductor for grounding and bonding on the supply side of the service disconnecting means. Your understanding is correct. The grounding conductor is permitted to be used for grounding and bonding on the supply side of the service disconnecting means. The grounded (neutral) conductor is required to be routed between enclosures and bonded to both, and this is common practice. The supporting NEC references are 250.92(B)(1) and 250.142(A)(1). Read more

Size of bonding wire for 200-amp load center
by Michael Johnston

The question appears to deal with a voltage-drop situation, but information is missing. I will answer the question by inserting the minimum necessary information. The first item to clarify is the terminology. I presume you are referring to the size of the equipment grounding conductor with the feeder and not a bonding wire which is undefined by the NEC. The next bit of information needed is the size of the ungrounded phase conductors intended to be installed for this feeder. Read more

Sunlight, Conductors and Raceways on Rooftops
by John Stacey

Let’s take a closer look at the NEC. The issue here is 310.10 that states, "No conductor shall be used in such a manner that its operating temperature exceeds that designed for the type of insulated conductor involved. In no case shall conductors be associated together in such, with respect to the type of circuit, the wiring method employed, or the number of conductors, that the limiting temperature of any conductors, that the limiting temperature of any conductor is exceeded.” Read more

2008, July-August

Would this be classified as a raceway?
by David G. Humphrey

The multiple questions concerning the installation as described by the submitter involve a number of considerations that make this installation very interesting (see photos 1-3). The submitter does not reference which NEC is being used, so we will base our answers upon the 2005 edition. Read more

Question: Can you daisy chain connections to fixtures?
by Michael Johnston

This response is based on the information provided in the question. 2 x 4 lay-in style fluorescent luminaires are permitted to be wired with any branch circuit wiring method in chapter 3 of the NEC, depending on the type of building construction it is being installed in. You indicated that the luminaires are being wired using MC cable that is run from one luminaire to the next, using the ballast compartment as a junction box. Read more

Static Electricity and UL 971
by Michael Johnston

This message is in response to your request for information about static electricity issues when plastic piping is used for transport. This subject is beyond the scope of NEC requirements. Often UL Standards writing has input from industry professionals that have expertise in a given field to attain the most meaningful input and to work on developing comprehensive product safety standards. Read more

Insulated bushing required when large conductor installed in EMT?
by Richard Owen

NEC-2002, Section 300.4(F) says: "…the conductors shall be protected by a substantial fitting providing a smoothly rounded insulating surface…” and does not specifically require a bushing. The bushing is only mentioned in the second paragraph in regard to a different requirement of 300.4(F). Read more

Does equipment need a second UL listing once it has been incorporated into final product?
by Lanny McMahill

First, the National Electrical Code defines approved as "acceptable to the authority having jurisdiction (AHJ).” Therefore, electrical products, equipment and installation approvals are the responsibility of the AHJ. See NEC Article 100 definition of approved and NEC 10.2 for approval requirements. Read more

When is an electrical vault required?
by Lanny McMahill

It is difficult to give a concrete response to "When is an electrical vault required,” as the use of a vault could be a design consideration or a mandatory Code requirement. There are conditions and other criteria that must be considered. Read more

Conduit system under slabs in patient care areas
by Eugene Morgan

NEC Sections 517.13(A) and (B) require the installation of branch circuits to receptacles and fixed equipment in a patient care area to have two separate and different grounding paths. One grounding path is a metal raceway system, or a cable having a metallic armor or sheath assembly that "shall itself qualify as an equipment grounding conductor in accordance with 250.118.” The other grounding path is, of course, the insulated copper grounding conductor. Read more

When was it that UL-approved panel shops became better (or the only) designers and fabricators of industrial control panels?
by Robert Fahey

The best way to answer your question regarding industrial control panels is by taking each part of the question and answering it separately. Answers are based on NEC-2008, although answers would not be different based on NEC-2005. Read more