Parallel grounding electrode

[Paul Bates]

I recently inspected a 800 amp 120/208 volt main breaker service with parallel 500 mcm feeders. The grounding electrode run to the water pipe was a 1/0 cu in a metal conduit. I requested that the grounding electrode be changed to 2/0 Cu per NEC table 250.66. The contractor then installed an additional # 1 Cu wire with the 1/0 cu in the pipe and contends the circular mill area equals or exceeds 2/0 cu and therefore is OK. I contend that parallel conductors are only permitted in size 1/0 cu and larger per NEC 310.4Is this the only article to prohibit this installation and or is the installation OK?

 

[raider1]

The contractors installation is a violation of 310.4.

First off you can't parallel a #1 and second the paralleled conductors must be the same size in circular mil area.

Also Table 250.66 gives the size of the grounding electrode conductor in AWG, I don't see how a 1/0 and a #1 would constitue a 2/0 AWG copper conductor.

Chris

 

[charlie b]

I agree with Chris that this is a violation of 310.4, but for a different reason. 310.4 says you can parallel phase conductors, and polarity conductors (whatever that is ? perhaps it relates to DC circuits), and neutral conductors, and grounded conductors. But it does not say you can parallel ?Grounding Electrode Conductors.? So even if the contractor proposed to parallel a pair of 1/0 conductors, instead of a #1 and a #1/0, 310.4 would not allow it.

Also, it violates the text of 250.66. That article says the GEC (singular, mind you) must be at least the size as shown in the table. It does not say you must accumulate enough cross-sectional area to achieve the same cross-sectional area as the wire shown in the table. It says the GEC must be the size shown in the table.

 

[don_resqcapt19]

Chris,
310.4 does not apply to grounding electrode conductors. The section only applies to the ungrounded and grounded conductors. Grounding conductors of any type are not covered by the rule in 310.4. That being said, I see no permission in Article 250 that says you can parallel a grounding electrode conductor. While I would argue that the code is a permissive code and if it is not prohibited it is permitted, but code making panel 6 does not agree with that position.

6-8 Log #2235 NEC-P06

Final Action: Reject
(310.4)​

___________________________________________________________

Submitter:

Donald A. Ganiere, Ottawa, IL​

Recommendation:​

Revise as follows:​

310.4 Conductors in Parallel. Aluminum, coper-clad aluminum, or copper

conductors of size 1/0 AWG and larger size #1 AWG and smaller, comprising each phase, polarity, neutral, or grounded circuit conductor, shall be permitted to not be connected in parallel (electrically joined at both ends).​

Substantiation:

There is no code rule that prevents the installation of conductors smaller than 1/0 AWG in parallel in the current code. The existing rule just specifically permits the use of conductors 1/0 and larger in parallel,
but does not prohibit smaller conductors from being paralleled.​

Panel Meeting Action: Reject

Panel Statement:
The present language meets the requirements of Section 3.1.3 of the NEC Style Manual. Article 310.4 permits conductors 1/0 or larger to be installed in parallel. The general rule is that conductors sized smaller than 1/0 are not permitted to be run in parallel.

Number Eligible to Vote: 11​

Ballot Results: Affirmative: 11​

note in the proposal wording in italics is to be deleted and wording underlined is new.
Don

​

 

[raider1]

Thanks Don,

I was wondering when I posted whether or not 310.4 could be applied to GEC's. That is why I also pointed out that Table 250.66 requires GEC's to be a certain size in AWG and not an equivalent in circular mils.

Chris

 

[charlie b]

Chris, 310.4 does not apply to grounding electrode conductors.

Thanks Don, I was wondering when I posted whether or not 310.4 could be applied to GECs.

That was my point. The fact that 310.4 does not apply to GECs tells me that an attempt to parallel GECs would be a violation of 310.4.

 

[haskindm]

Since the grounding electrode conductors are installed in a metal conduit, they/it will also need to be bonded to each end of the conduit.

 

[don_resqcapt19]

Charlie,

The fact that 310.4 does not apply to GECs tells me that an attempt to parallel GECs would be a violation of 310.4.

And I read it the other way. I have been taught that the code is a permissive code, that is, if it is not prohibited, then it is permitted. I think panel 6 was worng to reject my proposal. There is no current code rule that says you cannot parallel conductors smaller than 1/0. There is a permission to parallel conductors 1/0 and larger, but that is not the same as saying you can't parallel conductors #1 and smaller. We are going down a very steep and slippery slope if the code has to be written to spell out everything that we are permitted to do.
Don

 

[iwire]

We are going down a very steep and slippery slope if the code has to be written to spell out everything that we are permitted to do.

Don

Don, I agree with all of your points in this thread.

If it goes that way we will need a trailer to carry the book and it will still never be able to cover every action we take in the field.

 

[charlie b]

I know nothing about their style manual. But I will observe two things.

First, 310.4 does include, as Exceptions, four instances in which conductors smaller than 1/0 are permitted to be paralleled. Those Exceptions would not be there, if the intent were that all conductors smaller than 1/0 may be paralleled in any and all circumstances.

Secondly, there are only five functions that a conductor can serve: ungrounded (which I take to include ?phase? and ?polarity?), grounded, neutral (to the extent that that differs from ?grounded?), EGC, and GEC. Three of these are named in 310.4; EGC and GEC are not. If it were to be permitted to parallel EGCs and GECs, either they would have been named in the list, or the others would not have been singled out and named.

 

[don_resqcapt19]

Charlie,

If it were to be permitted to parallel EGCs...

Not only are we permitted to parallel EGCs, we are required to do so in some cases...see 250.122(F).
As far as the NEC Manual of Style, you can view or download it here.
Don

 

[Bea]

Not only are we permitted to parallel EGCs, we are required to do so in some cases...see 250.122(F).
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I would say this is one example why EGC is not included in 310.4 as these EGC would in most cases paralleled and small the 1/0

 

[petersonra]

AFAIK, there is no rule prohibiting the use of parallel EGCs or GECs. However, you still have to have a single conductor of the correct size in there somewhere.