Parallel Equipment Grounding Conductor Sizing Question

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Can parallel equipment grounding conductors be smaller than 1/0 awg?

For example, I have a an 800 amp disitribution panel feeding a 400 amp sub distribution panel with two runs of 4/0 awg feeders and neutral and a #3 awg equipment grounding conductor run with the feeders and neutrals in each conduit. The #3 awg is sized by Table 250.122. Is this correct, or are the equipment grounding conductors required to be a minimum of 1/0 awg per 310.10(H) Conductors in parallel?

250.122(F) Conductors in parallel state that each equipment grounding conductor shall be sized in compliance with 250.122.
310.10(H) Condcutors in parallel states that conductors in parallel shall be 1/0 awg or larger.
310.10(H)(5) discusses Equipment Grounding Conductors in parallel and states they shall be sized by 250.122. Then it describes multiconductor cable (I am presuming Types G or W or similar) where there are multiple small equipment grounding conductors and that they can be smaller than 1/0.

Respectfully,

Cohosilver
 

LEO2854

Esteemed Member
Location
Ma
Can parallel equipment grounding conductors be smaller than 1/0 awg?

For example, I have a an 800 amp disitribution panel feeding a 400 amp sub distribution panel with two runs of 4/0 awg feeders and neutral and a #3 awg equipment grounding conductor run with the feeders and neutrals in each conduit. The #3 awg is sized by Table 250.122. Is this correct, or are the equipment grounding conductors required to be a minimum of 1/0 awg per 310.10(H) Conductors in parallel?

250.122(F) Conductors in parallel state that each equipment grounding conductor shall be sized in compliance with 250.122.
310.10(H) Condcutors in parallel states that conductors in parallel shall be 1/0 awg or larger.
310.10(H)(5) discusses Equipment Grounding Conductors in parallel and states they shall be sized by 250.122. Then it describes multiconductor cable (I am presuming Types G or W or similar) where there are multiple small equipment grounding conductors and that they can be smaller than 1/0.

Respectfully,

Cohosilver

From 250.122 table if your load is 400 amps then you need a #3 copper equipment ground conductor.
 

iwire

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Staff member
Location
Massachusetts
310.10(H) Condcutors in parallel states that conductors in parallel shall be 1/0 awg or larger.


Please note that 310.10(H)(1) does not apply to equipment grounding conductors.


310.10(H) Conductors in Parallel.
(1) General.
Aluminum, copper-clad aluminum, or copper
conductors, for each phase, polarity, neutral, or grounded circuit
shall be permitted to be connected in parallel (electrically
joined at both ends) only in sizes 1/0 AWG and larger where
installed in accordance with 310.10(H)(2) through (H)(6).

That being the case EGCs of any size can be in parallel, if you think about it small EGCs are very often electrically in parallel.
 
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Dennis Alwon

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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Agreed, the egc is a separate animal but if you have separate conduits the conductor in each conduit must be sized to the OCPD. You do not really parallel them in that sense.
 
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