Wire-Smith
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- United States
Same answer as post 75
Two switchboards
- Thread starter hhsting
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hhsting
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- Glen bunie, md, us
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- Junior plan reviewer
One conductice path i see is GE to busbar to GE of 2nd disco.
Bldg steel is an electrode and so is underground metal pipe.
I dont see how thise can be condutive paths unless I have panelboard on steel bonded ir some metal conduit touches bldg steel.
Is their an example? I dont see what other conductive paths to main bonds.
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Wire-Smith
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Your branch circuit or feeder egc's and whatever they bond directly and indirectly(ie, conduit box mounted to steel bonds steel and steel bonds everything that touches it, your pump egc indirectly bonding sprinkler pipe, etc)
hhsting
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- Glen bunie, md, us
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- Junior plan reviewer
So once installed measure current in exterior Swbd service disco phase and neutral. Add phase current should equal neutral.
Measure current in FP service disco phase and neutral. Add phase current should equal neutral.
In either case phase current not equal neutral then objectionable current is causing it and investigstion is needed.
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hhsting
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- Glen bunie, md, us
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- Junior plan reviewer
Wire-Smith
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Most people wouldn't investigate it but I would at least a little. Heavily loading the neutral on your highest neutral current panel with the other panel neutral load turned off is how I would check, and then since your fp panel looks furthest away from service I would turn other panel off and load fp panel neutral if it has any. Check the current on the wires on the service side of the disconects and main bonds, I would also check current on the gec's to your ground bus bar in the drawing, that's the likely path I see to bear the bulk of the unintentional parallel neutral
Wire-Smith
Senior Member
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- United States
What are you calling GPE?
Wire-Smith
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- United States
And just to clarify again, if some of your neutral current does migrate through the unintentional paths, that alone does not make it objectionable current, it's only objectionable if it would cause a problem. I would be surprised if none of your neutral current migrates, but that alone doesn't mean it's objectionable. I would guess, depending on your neutral load, you will have a few amps migrate.
hhsting
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- Glen bunie, md, us
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- Junior plan reviewer
Nec 2014 Article 230.95 based on this article:
https://www.ecmweb.com/content/get-heart-objectionable-current
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Wire-Smith
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- United States
hhsting
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- Glen bunie, md, us
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- Junior plan reviewer
That means objectionable current only on 800A swbd NOT the FP swbd.
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hhsting
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- Glen bunie, md, us
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- Junior plan reviewer
Wire-Smith
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- United States
I will read the article but I would guess they are talking about a second unintentional bond, the difference in your scenario is you knowingly are designing it for two bonds.
I'm not saying don't use gfpe, I'm just throwing the possible wrench in about possibly what many might call "nuisance" tripping, because again the current is only objectionable if it will cause a problem.
What do you think about my suggestion of bonding at utility xfmr? Or an isolation transformer?
I'm not saying don't use gfpe, I'm just throwing the possible wrench in about possibly what many might call "nuisance" tripping, because again the current is only objectionable if it will cause a problem.
What do you think about my suggestion of bonding at utility xfmr? Or an isolation transformer?
hhsting
Senior Member
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- Glen bunie, md, us
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- Junior plan reviewer
Article says neutral to gnd bond not in service disco or in transformer and secondary panelboard both locations .
I have neutral to gnd bond on SERVICE SWBDS. Both OF THEM ARE FED BY SERVICE. BOTH ARE SERVICE DISCONNECT
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Wire-Smith
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I don't know why you would want to go the route of gfpe when my other suggestions would design out the actual problem but since your looking that way you could also use ground fault alarm instead of trip
Wire-Smith
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- United States
Edit
hhsting
Senior Member
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- Glen bunie, md, us
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- Junior plan reviewer
Ok well do you agree that Swbd #1 main breaker is service disconnect #1 and Swbd #2 also has main breaker and is service disconnect #2?
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Wire-Smith
Senior Member
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I wish I would have known about that article 70 posts ago and just referenced to that, LOL. Thanks
Wire-Smith
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- United States
Yes, I think where we are seeing different is that article doesn't exactly correleate with your situation, its talking about typical single service premises, although related, the information does not translate exactly for your situation.
Wire-Smith
Senior Member
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- United States
You never replied to my question about my other two suggestions, what do you think about those? The one is just pulling extra wire with service and adding surge protectors and getting permission from AHJ
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