petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
is there any code provision allowing an EGC to be made up of parallel wires as opposed to a single wire?
Parallel EGC
- Thread starter petersonra
- Start date
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wirenut1980
Senior Member
- Location
- Plainfield, IN
Re: Parallel EGC
205-122(f) in the 1999 NEC might be considered kind of like what you are saying, but it's for parallel runs of ungrounded conductors.
205-122(f) in the 1999 NEC might be considered kind of like what you are saying, but it's for parallel runs of ungrounded conductors.
- Location
- Massachusetts
Re: Parallel EGC
I do not see any way in to comply with Table 250.122 using parallel EGCs, there are no notes to the table explaining how to figure how many of one conductor equals another.
Even when running parallel EGCs with parallel feeders each EGC is large enough to be the sole EGC or GFP must be provided.
I do not see any way in to comply with Table 250.122 using parallel EGCs, there are no notes to the table explaining how to figure how many of one conductor equals another.
Even when running parallel EGCs with parallel feeders each EGC is large enough to be the sole EGC or GFP must be provided.
Bob
charlie
Senior Member
- Location
- Indianapolis
Re: Parallel EGC
sure as long as they are 1/0 or larger and they are with all of the phase conductors (like in a cable tray). If you have individual runs of conduit, it would not be practical since the grounding conductor has to be large enough for the overcurrent device and in each run.
sure as long as they are 1/0 or larger and they are with all of the phase conductors (like in a cable tray). If you have individual runs of conduit, it would not be practical since the grounding conductor has to be large enough for the overcurrent device and in each run.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Parallel EGC
The rules of 310.4 seem only to apply to "phase, neutral, or grounded conductor..." With that in mind, I don't believe you can do it.
The rules of 310.4 seem only to apply to "phase, neutral, or grounded conductor..." With that in mind, I don't believe you can do it.
charlie
Senior Member
- Location
- Indianapolis
Re: Parallel EGC
Ryan, you didn't read far enough. This is found towards the end of 310.4:
"Where equipment grounding conductors are used with conductors in parallel, they shall comply with the requirements of this section except that they shall be sized in accordance with 250.122."
You owe me a beer the next time we meet.
Ryan, you didn't read far enough. This is found towards the end of 310.4:
"Where equipment grounding conductors are used with conductors in parallel, they shall comply with the requirements of this section except that they shall be sized in accordance with 250.122."
You owe me a beer the next time we meet.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: Parallel EGC
250.122 would seem to require GF protection for paralleled EGC that are smaller than what would normally be allowed for the OCPD size on the circuit.Originally posted by charlie:
Ryan, you didn't read far enough. This is found towards the end of 310.4:
"Where equipment grounding conductors are used with conductors in parallel, they shall comply with the requirements of this section except that they shall be sized in accordance with 250.122."
You owe me a beer the next time we meet.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Parallel EGC
Charlie: Here in the office all I have is the handbook. I have the NEC in my truck, and at my home and on my home computer. I have a hard time with the handbook sometimes...you start reading the text, then skip the commentary, then read more text, then skip more commentray, then miss the last sentance of the text!
Alright, I'll buy you a beer next time we meet...I think it's my turn anyway
Charlie: Here in the office all I have is the handbook. I have the NEC in my truck, and at my home and on my home computer. I have a hard time with the handbook sometimes...you start reading the text, then skip the commentary, then read more text, then skip more commentray, then miss the last sentance of the text!
Alright, I'll buy you a beer next time we meet...I think it's my turn anyway
john m. caloggero
Senior Member
Re: Parallel EGC
Section 310.4 allows the use of parallel equipment grounding conductors provided each conductor is at least 1/0 or larger. The size of the parallel EGC is based on the cross-sectional of that required by Table 250.122. Example: feeder supplied from a 2000 amp breaker requires a 250 kcmil EGC (table 250.122). From Chapter 9, Table 8, one 2/0 conductors has a cross-sectional area of 133,100 circular mils; therefore, two 2/0 EGC's in parallel equals 266,200 circular mils, thereby satisfying the minimum requirement of 250,000 circula mils (250 kcmils). Remember, each EGC connected in parallel cannot be smaller than 1/0.(see exceptions).
Section 310.4 allows the use of parallel equipment grounding conductors provided each conductor is at least 1/0 or larger. The size of the parallel EGC is based on the cross-sectional of that required by Table 250.122. Example: feeder supplied from a 2000 amp breaker requires a 250 kcmil EGC (table 250.122). From Chapter 9, Table 8, one 2/0 conductors has a cross-sectional area of 133,100 circular mils; therefore, two 2/0 EGC's in parallel equals 266,200 circular mils, thereby satisfying the minimum requirement of 250,000 circula mils (250 kcmils). Remember, each EGC connected in parallel cannot be smaller than 1/0.(see exceptions).
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Parallel EGC
I?m not sure who I am disagreeing with here, but if I prove to be right, I prefer Maker?s Mark to a beer.
I don?t think you can combine two or more conductors in parallel, to form a single EGC. As Ryan pointed out, 310.4 (2002 version) explicitly states that you can parallel a ?phase, neutral, or grounded? conductor. I am not sure why it says both ?neutral? and ?grounded,? as I thought these terms to be synonymous. But EGC is very conspicuous in its non-inclusion in this list.
The next to last sentence of 310.4, as discussed above by Ryan and the other Charlie, does not, in my view, permit the use of a set of smaller, parallel, EGC conductors. It merely states that if you include an EGC in the raceway that contains the phase, neutral, or grounded conductors, then the EGC must be sized per 250.122. There is nothing in 250.122 that permits the use of a set of smaller, parallel, EGC conductors. What it requires is a full-sized EGC in each raceway.
I think the key words that I am interpreting differently than Ryan and Charlie are the words, ?Where (EGCs) are used with conductors in parallel. . . .? This is not the same as saying, ?Where parallel conductors are used to form an EGC.? Rather, I read this sentence as saying, ?Where a single, full-sized EGC is used with phase conductors that are installed as sets of paralleled conductors. . . .?
I?m not sure who I am disagreeing with here, but if I prove to be right, I prefer Maker?s Mark to a beer.
I don?t think you can combine two or more conductors in parallel, to form a single EGC. As Ryan pointed out, 310.4 (2002 version) explicitly states that you can parallel a ?phase, neutral, or grounded? conductor. I am not sure why it says both ?neutral? and ?grounded,? as I thought these terms to be synonymous. But EGC is very conspicuous in its non-inclusion in this list.
The next to last sentence of 310.4, as discussed above by Ryan and the other Charlie, does not, in my view, permit the use of a set of smaller, parallel, EGC conductors. It merely states that if you include an EGC in the raceway that contains the phase, neutral, or grounded conductors, then the EGC must be sized per 250.122. There is nothing in 250.122 that permits the use of a set of smaller, parallel, EGC conductors. What it requires is a full-sized EGC in each raceway.
I think the key words that I am interpreting differently than Ryan and Charlie are the words, ?Where (EGCs) are used with conductors in parallel. . . .? This is not the same as saying, ?Where parallel conductors are used to form an EGC.? Rather, I read this sentence as saying, ?Where a single, full-sized EGC is used with phase conductors that are installed as sets of paralleled conductors. . . .?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: Parallel EGC
I tend to agree with Charlie on this one. The wording seems reasonably clear that you cannot run multiple smaller EGCs to make an equivilant larger EGC as you can with actual current carrying conductors. The wording is somewhat obtuse though.
Maybe it just doesn't come up that often since the EGC is usually quite a bit smaller anyway.
I tend to agree with Charlie on this one. The wording seems reasonably clear that you cannot run multiple smaller EGCs to make an equivilant larger EGC as you can with actual current carrying conductors. The wording is somewhat obtuse though.
Maybe it just doesn't come up that often since the EGC is usually quite a bit smaller anyway.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Parallel EGC
Very good point!
charlie
Senior Member
- Location
- Indianapolis
Re: Parallel EGC
Maker?s Mark it is and I forget what Ryan was drinking.
Maker?s Mark it is and I forget what Ryan was drinking.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Parallel EGC
I'll take a Sam Adam's....always a good decision
I'll take a Sam Adam's....always a good decision
- Location
- Illinois
- Occupation
- retired electrician
Re: Parallel EGC
What words prohibit installing EGCs in parallel? The wording in 310.4 is only premissive. It clearly permits parlleling the ungrounded and grounded circuit conductors, but it does not prohibit the paralleling of the EGC.
Don
What words prohibit installing EGCs in parallel? The wording in 310.4 is only premissive. It clearly permits parlleling the ungrounded and grounded circuit conductors, but it does not prohibit the paralleling of the EGC.
Don
charlie
Senior Member
- Location
- Indianapolis
Re: Parallel EGC
Don, I think the way the Code is worded, it is inferred.
Don, I think the way the Code is worded, it is inferred.
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Parallel EGC
I don't know.......This one says more than one:
250.119 (B) Multiconductor Cable. Where the conditions of maintenance and supervision ensure that only qualified persons service the installation, one or more insulated conductors in a multiconductor cable, at the time of installation, shall be permitted to be permanently identified as equipment grounding conductors at each end and at every point where the conductors are accessible by one of the following means:
(1) Stripping the insulation from the entire exposed length
(2) Coloring the exposed insulation green
(3) Marking the exposed insulation with green tape or green adhesive labels
I don't know.......This one says more than one:
250.119 (B) Multiconductor Cable. Where the conditions of maintenance and supervision ensure that only qualified persons service the installation, one or more insulated conductors in a multiconductor cable, at the time of installation, shall be permitted to be permanently identified as equipment grounding conductors at each end and at every point where the conductors are accessible by one of the following means:
(1) Stripping the insulation from the entire exposed length
(2) Coloring the exposed insulation green
(3) Marking the exposed insulation with green tape or green adhesive labels
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Parallel EGC
But here?s a new twist that just occurred to me. As I mentioned earlier, the list includes phase, neutral, and grounded. But I think the last two are the same thing. Could the code committee have meant phase, grounded, and EGC? Could this have been a typo?
Here?s another tidbit: The 1987 version just listed ?phase or neutral.? The 1990 version changed this to ?phase, neutral, or grounded.? I am no longer a member of the NFPA, so I can?t look into the basis for this code change. Anyone want to take on this task?
I agree. Since they went out of their way to explicitly state that it is OK to parallel some conductors, and then gave specific rules and exceptions under which this is acceptable, I believe they did imply that an EGC should not be on the list. Or so I infer.
But here?s a new twist that just occurred to me. As I mentioned earlier, the list includes phase, neutral, and grounded. But I think the last two are the same thing. Could the code committee have meant phase, grounded, and EGC? Could this have been a typo?
Here?s another tidbit: The 1987 version just listed ?phase or neutral.? The 1990 version changed this to ?phase, neutral, or grounded.? I am no longer a member of the NFPA, so I can?t look into the basis for this code change. Anyone want to take on this task?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: Parallel EGC
It seems to me there is no prohibition on paraleling EGCs, which is in fact a common practice. There does not seem to be any allowance for using multiple smaller EGC in lieu of a larger EGC that might be required.
i.e. - you can't replace a single 500MCM EGC with (2) 250MCM.
It seems to me there is no prohibition on paraleling EGCs, which is in fact a common practice. There does not seem to be any allowance for using multiple smaller EGC in lieu of a larger EGC that might be required.
i.e. - you can't replace a single 500MCM EGC with (2) 250MCM.
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