250.122

[Isaiah]

Construction put 3, 500kCMIL, per phase along with 3 EGCS is a single 6” RGS conduit from an undersized pull box to the panelboard - the conduit is only about 2’ long - is this a code violation?


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[roger]

Only one EGC is needed, be it the RMC or a propper sized wire.

 

[roger]

Besides the undersized pull box there is no violation to have multiple EGC's.

 

[Isaiah]

Besides the undersized pull box there is no violation to have multiple EGC's.

Is there a problem with having 9 , 500kCMIL in a single conduit (3 per phase) as long as derating is applied?


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[augie47]

No fill problem and if the nipple is not over 24" long, no derating required.

 

[Isaiah]

No fill problem and if the nipple is not over 24" long, no derating required.

These are single conductors, 500kCMIL 3 per phase. Is there any concern with inductance and hot spots if they’re all laid in the same conduit?


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[Strathead]

These are single conductors, 500kCMIL 3 per phase. Is there any concern with inductance and hot spots if they’re all laid in the same conduit?


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no.

 

[Isaiah]

no.

Can you elaborate on why not? Is this because of the short distance or simply because the insulation is sufficient protection?


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[SSDriver]

They only need one EGC but I'm assuming this was there transition from parallel runs. If so each EGC needs to be sized as a full EGC.

 

[SSDriver]

Can you elaborate on why not? Is this because of the short distance or simply because the insulation is sufficient protection?


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Nipples 24" and under do not require derating of conductors.

310.15c states derating is for lengths longer than 24"

 

[Isaiah]

Nipples 24" and under do not require derating of conductors.

310.15c states derating is for lengths longer than 24"

Understood but my question is not about derating


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[SSDriver]

Understood but my question is not about derating


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Then what would be the problem.

Conductance - no, all circuit wires are in the same conduit.

Heating- no, nipple is too short to contain any heat build up hence why nipples shorter than 24" don't require derating.

 

[infinity]

These are single conductors, 500kCMIL 3 per phase. Is there any concern with inductance and hot spots if they’re all laid in the same conduit?

No, parallel conductors are permitted in a single raceway. Since you're not more than 24" no sweating applies. Fill can be up to 60% so that's not an issue either.

 

[Isaiah]

No parallel conductors are permitted in a single raceway. Since you're not more than 24" no sweating applies. Fill can be up to 60% so that's not an issue either.

Thanks infinity
“No parallel conductors are permitted in a single raceway”
Where exactly is that found?
(Using 2023 NEC)


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[Isaiah]

No parallel conductors are permitted in a single raceway. Since you're not more than 24" no sweating applies. Fill can be up to 60% so that's not an issue either.

If the 24” nipple is considered a raceway, is this a code violation?


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[augie47]

310.10(H) addresses conductors in parallel and the wording allows them to be in the same conduit.
As noted above, 310.15.(B)(3)(a) addresses derating and notes derating is not necessary when the raceway is 24" or less in length/
Chapter 9, Table 1 will confirm there is no problem with fill.

 

[Isaiah]

310.10(H) addresses conductors in parallel and the wording allows them to be in the same conduit.
As noted above, 310.15.(B)(3)(a) addresses derating and notes derating is not necessary when the raceway is 24" or less in length/
Chapter 9, Table 1 will confirm there is no problem with fill.

I don’t find 310.10(H) in either 2020 or 2023.
What concerns me is 366.20 which requires conductors in parallel to be separate groups to prevent current imbalance due to inductive reactance
Does this apply to a short conduit nipple?


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[augie47]

In 2020, it's 310.15(G)
With all your conductors sharing the nipple, they would be grouped as required by 366

 

[Isaiah]

In 2020, it's 310.15(G)
With all your conductors sharing the nipple, they would be grouped as required by 366

Makes sense


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[infinity]

Thanks infinity
“No parallel conductors are permitted in a single raceway”
Where exactly is that found?

There is a missing comma it should say No,

I'll fix it.