Nec 2014 compliant?

hhsting

Senior Member
Attached sketch shows service entrance conductors going into trough. In the trough has ground bar which has supply side bonding jumper to trough enclosure and one grounding electrode conductor going to underground metal water pipe and other is a bonding jumper going to ground rods from the ground bar. The ground bar then has supply side bonding jumper and neutral going to each service disconnects as shown.

Question is does the attached sketch comply per Nec 2014 Articles 250.64(D)(3) and 250.53(D)(2)?

Thank you for code expert input



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mopowr steve

Senior Member
Location
NW Ohio
It looks like you have a neutral from your trough and then another ground wire going to the same block in the disconnects, not allowed and unnecessary. That would be paralleled conductors with objectionable current on your bonding wire.
Loose the bonding wire to the disconnects as you can use the bonding screw that comes with the disconnect to bond it’s metal case to the grounded conductor block within it. Also you may need to use bonding bushings on one end of the nipples between the trough and disconnect if they are metallic.
 

hhsting

Senior Member
250.64(D)(3) requires a grounding electrode conductor (one) but two are shown. However, 250.53(D)(2) says supplemental electrode req for underground metal water pipe bonded to grounding electrode conductor. Would all the above make sketch non compliant to code?

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jaggedben

Senior Member
See 250.64(F)(2). It's a little debatable if this supersedes the 'A grounding electrode conductor..." in 250.64(D)(3), but since the GECs all go to a common point and don't create any parallel paths (besides earth), that would be a really ticky-tack argument.
 

kwired

Electron manager
Location
NE Nebraska
It looks like you have a neutral from your trough and then another ground wire going to the same block in the disconnects, not allowed and unnecessary. That would be paralleled conductors with objectionable current on your bonding wire.
Loose the bonding wire to the disconnects as you can use the bonding screw that comes with the disconnect to bond it’s metal case to the grounded conductor block within it. Also you may need to use bonding bushings on one end of the nipples between the trough and disconnect if they are metallic.
Not sure exactly what he has there, the details mostly involve the grounded conductors, but am assuming all service conductors enter the trough, run to service disconnects than back to trough - can't put line and load side conductors of service disconnect in same raceway - but can be in the same trough. Enclosures containing service conductors are supposed to be bonded to the grounded conductor (can be via SSBJ's).

If the service disconnects were top feed and he put similar ground bar in the trough, but only landed GEC's and/or EGC's on it - still have parallel paths for grounded conductor current to flow, but NEC doesn't necessarily see that as objectionable current paths.

Looks like maybe he has line and load side grounded conductors ran from the "ground bar" in trough to each disconnect - kind of redundant but not necessarily any code violation. Presuming actual grounded conductors to outgoing feeders also comes off the "ground bar" in the trough. If so all that would be needed to disconnects is a conductor sized per 250.66, they would have no load on them other than "stray currents" that would not be considered objectionable. Good design still may try to eliminate that possibility though.
 
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