The new NEC requires, in the subject article, that the feeder neutral be sized per Table 250.122 in the same way as the grounding conductor, which makes sense. Does anyone know why this article excludes the neutral from compliance with 250.122(F) in case of paralleled feeders? I haven't been able to find this discussed in the Committee "Report on Proposals".
NEC 2005/ 215.2(A)(1) General
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bphgravity
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Re: NEC 2005/ 215.2(A)(1) General
In my opinion, this is a matter of compromise.
I believe the original intent of requiring the grounded conductor to not be smaller than that required for the EGC is that the impedance of small conductors would be too great to allow OCD operation. However, in some instances, requiring a grounded conductor to be sized from Table 250.122 would be somewhat extreme to handle the fault current imposed, considering there is already a 1/0 AWG minium already in place for parralleled conductors.
In my opinion, this is a matter of compromise.
I believe the original intent of requiring the grounded conductor to not be smaller than that required for the EGC is that the impedance of small conductors would be too great to allow OCD operation. However, in some instances, requiring a grounded conductor to be sized from Table 250.122 would be somewhat extreme to handle the fault current imposed, considering there is already a 1/0 AWG minium already in place for parralleled conductors.
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Re: NEC 2005/ 215.2(A)(1) General
Why would the grounded conductor of a feeder play any part in clearing a fault??? There is no good electrical reason to size a feeder grounded conductor larger than required by the calculated load.
Don
Why would the grounded conductor of a feeder play any part in clearing a fault??? There is no good electrical reason to size a feeder grounded conductor larger than required by the calculated load.
Don
bphgravity
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Re: NEC 2005/ 215.2(A)(1) General
Line-to-grounded conductor short circuits.
Line-to-grounded conductor short circuits.
Re: NEC 2005/ 215.2(A)(1) General
bphgravity is correct,the requirement is to size the neutral at no less than the grounding conductor so that it will have sufficient capacity to withstand damage in case of a phase to neutral fault -- the same as for the grounding conductor. I'm still unclear as to why it shouldn't also meet 250.122(F).
bphgravity is correct,the requirement is to size the neutral at no less than the grounding conductor so that it will have sufficient capacity to withstand damage in case of a phase to neutral fault -- the same as for the grounding conductor. I'm still unclear as to why it shouldn't also meet 250.122(F).
wirenut1980
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Re: NEC 2005/ 215.2(A)(1) General
Doesn't 215.2(A)(1) say: feeder circuit grounded conductors shall not be smaller than the required feeder equipment grounding conductor specified in 250.122.
To me that means the entire article 250.122 and not just Table 250.122. Which means that increasing the EGC size for feeder parallel feeds in accordance with 250.122(F) would necessitate increasing the feeder grounded conductor size in accordance with 215.2(A)(1).
Doesn't 215.2(A)(1) say: feeder circuit grounded conductors shall not be smaller than the required feeder equipment grounding conductor specified in 250.122.
To me that means the entire article 250.122 and not just Table 250.122. Which means that increasing the EGC size for feeder parallel feeds in accordance with 250.122(F) would necessitate increasing the feeder grounded conductor size in accordance with 215.2(A)(1).
charlie
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- Indianapolis
Re: NEC 2005/ 215.2(A)(1) General
Bryan, I can't bring myself to agree with you but I can't argue against your statement either (Line-to-grounded conductor short circuits).
The problem I have with the new language is that it sounds like a neutral is now required to be taken with all feeder circuits. If it can't be smaller than . . , wouldn't that seem to indicate that it is required?
Bryan, I can't bring myself to agree with you but I can't argue against your statement either (Line-to-grounded conductor short circuits).
The problem I have with the new language is that it sounds like a neutral is now required to be taken with all feeder circuits. If it can't be smaller than . . , wouldn't that seem to indicate that it is required?
Re: NEC 2005/ 215.2(A)(1) General
To David Z,
The exact 215.2(A)(1)clause reads "The size of the feeder circuit grounded conductor shall not be smaller than that required by 250.122, except that 250.122(F) shall not apply where grounded conductors are run in parallel."
So, for whatever reason, the neutral doesn't have to meet the grounding conductor size requirements for parallel circuits.
To bphgravity,
The "1/0 minimum" in your earlier post actually applies to "services" per 250.24(C)(2).
To Charlie,
I can't find anywhere in the NEC that requires a neutral in a feeder if it's not needed to serve single phase loads. It is required as the grounded conductor in "services" per 250.24(C).
To David Z,
The exact 215.2(A)(1)clause reads "The size of the feeder circuit grounded conductor shall not be smaller than that required by 250.122, except that 250.122(F) shall not apply where grounded conductors are run in parallel."
So, for whatever reason, the neutral doesn't have to meet the grounding conductor size requirements for parallel circuits.
To bphgravity,
The "1/0 minimum" in your earlier post actually applies to "services" per 250.24(C)(2).
To Charlie,
I can't find anywhere in the NEC that requires a neutral in a feeder if it's not needed to serve single phase loads. It is required as the grounded conductor in "services" per 250.24(C).
charlie
Senior Member
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- Indianapolis
Re: NEC 2005/ 215.2(A)(1) General
JWilson, look carefully at what that section is saying. If I tell you that the glass of water is to have two ice cubes, doesn't that imply that you have to have a glass of water? This section now tells you the minimum size of the grounded conductor, doesn't that imply that you have to have a grounded conductor?
JWilson, look carefully at what that section is saying. If I tell you that the glass of water is to have two ice cubes, doesn't that imply that you have to have a glass of water? This section now tells you the minimum size of the grounded conductor, doesn't that imply that you have to have a grounded conductor?
charlie
Senior Member
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- Indianapolis
Re: NEC 2005/ 215.2(A)(1) General
By the way, 310.4 doesn't apply just to services.
By the way, 310.4 doesn't apply just to services.
Re: NEC 2005/ 215.2(A)(1) General
To Charlie,
Regarding the "glass of water" thing, if there is a glass of water then I agree it's to have two ice cubes. The wording of 215.2(A)(1) does not mandate the use of a neutral if it's not used. A neutral would not be installed in a feeder to a delta primary transformer. What would you connect it to?
Regarding 310.4 "Conductors in Parallel", it's not germane to this discussion.
To Charlie,
Regarding the "glass of water" thing, if there is a glass of water then I agree it's to have two ice cubes. The wording of 215.2(A)(1) does not mandate the use of a neutral if it's not used. A neutral would not be installed in a feeder to a delta primary transformer. What would you connect it to?
Regarding 310.4 "Conductors in Parallel", it's not germane to this discussion.
charlie
Senior Member
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- Indianapolis
Re: NEC 2005/ 215.2(A)(1) General
Jim, I think you may have to defend your position one of these days. I am just saying that it implies that interpretation. I am on your side on this argument.
310.4 was in response to your response to Bryan.
Jim, I think you may have to defend your position one of these days. I am just saying that it implies that interpretation. I am on your side on this argument.
310.4 was in response to your response to Bryan.
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