Question 1. I am looking for an answer to the following question. Section 250.52(A)(3) on a concrete-encased electrode says that it must be 1/2" rebar, 20 feet in length or a 4 AWG bare copper, 20 feet in length. If the available rebar were larger than 1/2" or longer than 20 feet, how would a person size the conductor to tap onto the rebar? Also, if the service were larger, should a conductor be larger or match the grounding electrode conductor used to bond water or building steel? — D. F.

Answer 1. The answer to the first part of your question is that the rebar must be not less than 50 mm (1/2" in.) in diameter and at least 6.0 m (20 ft) in length. Where the rebar exceeds these dimensions, it exceeds the minimum requirements of the NEC, which is acceptable. The second part of your question deals with sizing the grounding electrode conductor that connects to a rebar. The size of the grounding electrode conductor does not depend on the size of the rebar. The size for this grounding electrode conductor should generally be not smaller than the sizes specified in Table 250.66, using the size of the largest ungrounded service-entrance conductor.

However, going back to the minimum requirements of the NEC, Section 250.66(B) relaxes this general requirement by requiring the grounding electrode conductor that is a sole connection to the concrete-encased electrode to be not larger than 4 AWG copper. Remember, the key to this sizing alternative in 250.66(B) is that the grounding electrode conductor is installed from the service directly to the concrete-encased electrode solely as indicated in this section. I hope this information helps clarify the minimum requirements of the NEC regarding sizing grounding electrode conductors that connect to concrete-encased electrodes. See Sections 250.52(A)(3), 250.66, and 250.66(B). This answer is based on the requirements in NEC-2005.
— Michael J. Johnston, CMP-5
(November/December 2006)

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Question 2. I am using plastic flexible piping (PEX) per the plumbing code which is passed by the local plumbing inspector. However, a question has been raised about grounding the PEX piping system. We use PEX piping in all the walls, and stub out of the wall with about 8 inches of copper (the connection between PEX and copper is made behind the wall). The electrical inspector is citing the NEC 250.104(A), saying that I need to install jumper (or bonding) 4 gauge wire from the copper stub out to the electrical panel to be grounded. The water service to the home is copper, and a ground connection is made at that point to the electrical service. Do I need to ground all the copper stub-outs in the home? NEC 250.104(A) is referring to a metal piping system, which PEX is not. The only metal in PEX are the fittings and the copper stub-outs. — JB

Answer 2. I presume that what you are actually asking is if you need to bond the short sections of metal piping (stubs) that are connected to the nonmetallic piping system installed in the building. The answer is no. A common misunderstanding of some electrical professionals is that the Code requires bonding of short sections of metal water pipe extensions that are connected to nonmetallic water piping systems installed within buildings. In the situation that you described, with the underground metal water piping already being used as a grounding electrode per Section 250.52(A)(1), requiring an additional 4 AWG copper conductor to be installed to bond a short section of metal pipe—which you had stated as being only eight inches long—is  unnecessary, and excessive. Section 250.104(A) requires the metal piping system to be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more electrodes used, but not to short metal piping stubs that are connected to plastic water piping systems.  

Other metal piping bonding requirements are provided in 250.102(B). This section applies to metal piping systems, other than metal water piping systems, such as air piping, gas piping, and so forth.

 Bonding for appliances such as electric hot water tanks or gas furnaces may be provided by the equipment grounding conductor included with the circuit wiring as per 250.104(B) and 250.134(A) and (B). Other electrical equipment, such as dishwashers, garbage disposals, or instant-hot water appliances, all require an equipment grounding conductor to be installed with the circuit wiring to the appliance, which would normally provide bonding to the water piping from the  appliance. These are generally considered as the circuits that are most likely to energize the piping associated with them. If bonding jumpers are needed to bond the piping because no equipment grounding conductor is present with the circuit wiring method, as is the case with some older wiring methods found in older structures, they should be sized as a minimum per 250.122.
— Michael J. Johnston, CMP-5
(March/April 2007)

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Question 3. I am a building official in the village of Islamorada in the Florida Keys. Possibly I am having a senior moment but at one time I thought I had seen an NEC section referencing the fact that a receptacle mounted horizontally was required to have the grounded (neutral) side in the (up) position. I have looked diligently and cannot locate the reference. If anyone can guide me, I would greatly appreciate any assistance, even if it means agreeing I am experiencing a senior moment. — G.A.

Answer 3. No, you are not having a “senior moment.” The Code is silent on the orientation of the grounded (neutral) slot position. It is permitted to be on the top or bottom. The same holds true for the grounding terminal on these receptacles. The grounding terminal can be on the top or the bottom. The Code does not require a specific orientation.
— Michael J. Johnston, CMP-5
(November/December 2007)

Question 4. Do the listed lugs (as required by 250.70) used in the attached picture from Soares Book on Grounding and Bonding (9th edition), page 127, need to be listed per UL 467? — J.S.

Answer 4. The Code currently requires the connections to the busbar to be made by a listed connector or the exothermic welding process. The irreversible compression connectors shown in the photo are listed; therefore, they meet this requirement. Connections of grounding electrode conductors (at the grounding electrode) to electrodes do have to meet the UL 467 requirements specifically where the connection is made in the earth or in the vicinity of the earth where it is likely to be subject to varying degrees of corrosive influences. As shown in photo 1 (the same photo used on page 127 of the Soares Grounding and Bonding book), the listed irreversible compression connectors meet the requirements of 250.64(C)(3). Currently efforts are being expended to add specific language to the NEC that calls for these connectors to be listed as grounding and bonding equipment. I hope this helps address your question.
— Michael J. Johnston, CMP-5
(November/December 2007)

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