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Sub-panel bonding

Merry Christmas
F

frofro19

Senior Member
Location
VA.
Occupation
Master Electrician
retirede said:
As long as the N-G bond is only in one place, there are no parallel paths to carry objectionable current.
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What if the disconnect is beside of another disconnect. In the case at my church, there's a 400 amp disconnect feeding another 400 amp disconnect right beside of it and the second 400 amp disconnect if feeding a 100 amp fuses disconnect right beside of that. The feeder in question is on the 100 amp disconnect beside of the other 400 amp disconnect. They are all bonded at each disconnect. I'm assuming all needed to n/g should have been connected together at the first 400 amp disconnect. This is a very old service to the church that was probably installed 100 years ago. Would there be objectionable current at the 3 disconnects grouped together if all 3 had n/g connected together in each disconnect?
 
R

retirede

Senior Member
Location
Illinois
frofro19 said:
What if the disconnect is beside of another disconnect. In the case at my church, there's a 400 amp disconnect feeding another 400 amp disconnect right beside of it and the second 400 amp disconnect if feeding a 100 amp fuses disconnect right beside of that. The feeder in question is on the 100 amp disconnect beside of the other 400 amp disconnect. They are all bonded at each disconnect. I'm assuming all needed to n/g should have been connected together at the first 400 amp disconnect. This is a very old service to the church that was probably installed 100 years ago. Would there be objectionable current at the 3 disconnects grouped together if all 3 had n/g connected together in each disconnect?
Click to expand...

Bond should exist only at the service disconnect. I’m guessing that the first 400 is the service disconnect?
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
frofro19 said:
... Would there be objectionable current at the 3 disconnects grouped together if all 3 had n/g connected together in each disconnect?
Click to expand...
If there is an EGC or other metal path between them, then yes, there would be objectionable current on that. If there is no EGC (like how you mentioned in the OP with SEU cable) there may be no objectionable current. On an old installation I would not unbond the neutral from the panel without installing some sort of EGC first. IMO fundamentally is more important that the panels be bonded than how they are bonded, notwithstanding that ideally they'd be brought up to code.
 
F

frofro19

Senior Member
Location
VA.
Occupation
Master Electrician
retirede said:
Bond should exist only at the service disconnect. I’m guessing that the first 400 is the service disconnect?
Click to expand...
I assume it is. Not sure why it's a 400 amp fused disconnect feeding a 40p amp fused disconnect. I'm going to take a pic the next time I'm there to make sure I'm seeing it right.
 
F

frofro19

Senior Member
Location
VA.
Occupation
Master Electrician
jaggedben said:
If there is an EGC or other metal path between them, then yes, there would be objectionable current on that. If there is no EGC (like how you mentioned in the OP with SEU cable) there may be no objectionable current. On an old installation I would not unbond the neutral from the panel without installing some sort of EGC first. IMO fundamentally is more important that the panels be bonded than how they are bonded, notwithstanding that ideally they'd be brought up to code.
Click to expand...
The 400 amp disconnects are connected with emt with no grounding bushings. The seu cables (several of them) are just ran through knock-outs. Several 100 amp services have been added on during the years, but they are all but one, the 3 conductor seu cables.
 
qcroanoke

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Sorta retired........
frofro19 said:
The 400 amp disconnects are connected with emt with no grounding bushings. The seu cables (several of them) are just ran through knock-outs. Several 100 amp services have been added on during the years, but they are all but one, the 3 conductor seu cables.
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Wow. No connectors on the cables?
From what you describe there is a mess on that wall.
Are you a contractor or just a well meaning member?
If all you had to fix was that one panel that's not a big deal but this sounds like it should be bought before the church at a business meeting and explained what is going on.
Then get 3 bids to fix it.
It doesn't sound like anything you want to take responsibility for.
 
F

frofro19

Senior Member
Location
VA.
Occupation
Master Electrician
qcroanoke said:
Wow. No connectors on the cables?
From what you describe there is a mess on that wall.
Are you a contractor or just a well meaning member?
If all you had to fix was that one panel that's not a big deal but this sounds like it should be bought before the church at a business meeting and explained what is going on.
Then get 3 bids to fix it.
It doesn't sound like anything you want to take responsibility for.
Click to expand...
It's definitely a mess that's been added on over the years. I'm a contractor but just a well meaning member on this one. There's even an old Pushmatic panel inside of some cabinets that i wouldn't dare touch that.
 
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