[RE-wrenches] Two Buildings, Two Services, One Roof

[Brian Teitelbaum]

Mark,

Are both buildings being fed from the same utility transformer?

I thank that may be a key question here

Brian Teitelbaum
AEE Solar

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Mark Frye
Sent: Monday, April 18, 2011 12:42 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Two Buildings, Two Services, One Roof

Thanks Ken,

I appreciate the information. But I am still not feeling very confident about this.

Yes, you can run a feeder with a EGC from one building with a service to an outbuilding and bond that EGC to a GE at the outbuilding, assuming that there is no service at that out building. If there is, then it is not an outbuilding?

My whole question boils down to that question: Is it OK to connect together the grounding systems of two seperate dwellings where each has it's own services? It is clear to me that I can't rely on the allowance for bonding of multiple seperately derived systems in this case because each building has it's own service and therefore cannot be considered as a seperately derived system. So where does the Code speak to this.

My sense is that it is a big no-no, but can exactly explain why.

Anyone else out there agree or disagree?

Mark Frye
Berkeley Solar Electric Systems
303 Redbud Way
Nevada City,  CA 95959
(530) 401-8024
www.berkeleysolar.com<http://www.berkeleysolar.com/>


________________________________
From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Kent Osterberg
Sent: Monday, April 18, 2011 12:09 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Two Buildings, Two Services, One Roof
Mark,

Separately derived is defined in article 100. Basically, a separately derived system has no common conductors other than possibly equipment ground.

By the definition in article 100 the feeder from the house may be a separately derived system at the shop. It may not be if the house and shop are feed off of the same transformer because the two systems would both have a neutral connection at the transformer.

The ac output of a grid interactive inverter with no batteries cannot be a separately derived system because it connects to conductors on the premises.

There must be an equipment ground with the inverter output wires (feeder between house and shop). And the equipment ground needs to connect to the grounding system at both buildings. That does make a connection between the two grounding systems - just as happens whenever a feeder is run from a house to an outbuilding.

Kent Osterberg
Blue Mountain Solar
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