Parallel Cables grounding

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mooreaaryan

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Bakersfield CA
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I have 2-cables each having (3)500mcm with 3 #2 bare ground. Each cable is in a separate conduit underground. I have terminated the phase conductors no issue. The grounding conductors have been twisted together and landed on a double barrel ground lug. Is there a code violation on this termination?
 
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petersonra

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mooreaaryan said:
I have 2-cables each having (3)500mcm with 3 #2 bare ground. Each cable is in a separate conduit underground. I have terminated the phase conductors no issue. The grounding conductors have been twisted together and landed on a double barrel ground lug. Is there a code violation on this termination?
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Probably a violation. I doubt the lug is listed for 3 conductors in a single hole.

When you run parallel conductors, each of the EGCs has to be sized per the rating of the OCPD for the circuit. #2 seems kind of small to me for whatever rating of OCPD (3) 500 MCM would have.
 
tom baker

tom baker

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The size of a EGC in parallel cables has been a frequent issue. Conductors in parallel require a full size egc in each raceway or cable. The reason is that in a ground fault, the fault can be fed from each end of the circuit.
 
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mooreaaryan

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petersonra said:
Probably a violation. I doubt the lug is listed for 3 conductors in a single hole.

When you run parallel conductors, each of the EGCs has to be sized per the rating of the OCPD for the circuit. #2 seems kind of small to me for whatever rating of OCPD (3) 500 MCM would have.
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Parallel cables with 3 #2 grounds. I am reaching out to manufacturer because instructions are contradicting code Either way I need to know the right way because I might have a lot of terms out there that aren’t up to code
 
tom baker

tom baker

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For your reference, code section 250.122 is where you size the EGC, based on your OCPD of 400 amps.
500 is oversized for an OCPD of 400 amps, typically 3/0 would be used with an EGC of 3 AWG. Perhaps 500 was used for Volt drop. If the circuit conductors are oversized the EGC is to be increased in proportion. See note to table 250.122
 
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mooreaaryan

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Bakersfield CA
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Electrician
tom baker said:
For your reference, code section 250.122 is where you size the EGC, based on your OCPD of 400 amps.
500 is oversized for an OCPD of 400 amps, typically 3/0 would be used with an EGC of 3 AWG. Perhaps 500 was used for Volt drop. If the circuit conductors are oversized the EGC is to be increased in proportion. See note to table 250.122
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Just out of curiosity…. Would a manufacturer ever make a cable that does give max protection on for max ampacity of conductors or how do they determine what size ground per phase they make. Seems to me that a lot of issues could be solved at manufactures level
 
augie47

augie47

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I can't put my finger on it in the Code but I thought it addressed multiconductor cables with multiple EGCs allowing the area of multiple smaller conductors to be combined. His cables have 3-#2 EGC which would have a combined area greater than the required 3/0.
Am I mistaken ??
 
don_resqcapt19

don_resqcapt19

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augie47 said:
I can't put my finger on it in the Code but I thought it addressed multiconductor cables with multiple EGCs allowing the area of multiple smaller conductors to be combined. His cables have 3-#2 EGC which would have a combined area greater than the required 3/0.
Am I mistaken ??
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You are correct. See the last sentence in 250.122(A).

I would be very surprised if the cable having 500 kcmil copper conductors has three 2 AWG EGCs. That would not be the common construction for that cable. The standard EGC for that cable is a single 2 AWG conductor. If it has three it was a custom manufactured cable.
More likely is that is has three conductors when combined result in a 2 AWG EGC.
 
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kenaslan

Senior Member
Location
Billings MT
A 3 grounded cable is usually for a VFD. Probably 3 #6 as that is the most common. Terminate the three grounds in an Ilsco multi lug. 3 #6 in 1 #2 out. as mentioned, twisting together is a code violation.
 
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