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

[Mark Frye]

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 
 <http://www.berkeleysolar.com/> 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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