Direct Grid Tie Ground Wire [RE-wrenches]

[Mark Frye]

Drake,

I read it as you read, it is both and it does have to be #8. We are lucky
that they are allowing it to be the same conductor. However, unless you can
get your AHJ to let you drop the #8 requirement on the DC ground electrode
conductor (or system ground)(seems reasonable to me for small sized systems)
then the 10/3 with ground won't cut it.

Either run the separate #8 GEC or run 8/3 with ground, or run flex and pull
#10's and the #8. I prefer the to run the flex and pull.

:-(
 
Mark Frye
Berkeley Solar Electric Systems
271 Vistamont Dr
Grass Valley CA 95945
(530) 401-8024
www.berkeleysolar.com
 

-----Original Message-----
From: Drake Chamberlin [mailto:Drake.Chamberlin at redwoodalliance.org] 
Sent: Monday, April 07, 2008 6:04 PM
To: RE-wrenches at topica.com
Subject: Direct Grid Tie Ground Wire [RE-wrenches]


Hello Wrenches,

I've been reading the 2008 code and talking to an inspector who is 
studying 690 very thoroughly.  A question arises about the grounding 
conductor between the AC service panel and the inverter.  Is it an 
equipment grounding conductor or a grounding electrode conductor, or both?

It would need to be both if there were both AC and DC systems.  This 
is covered in 690.47(C), "Systems with Alternating-Current and 
Direct-Current Grounding Requirements."  Unless the array had plastic 
frames, it would seem that there would always be DC grounding 
requirements, so what does this mean?

This is direct grid tie with no DC loads.  It seems another section 
would need to be added to deal with a direct grid tie system.

The main issue that arises from this is that if the ground wire is 
considered a grounding electrode conductor, it needs to be #8.  This 
would mean that a 10/3 WG cable would need to have a separate ground 
wire run that is at least #8.  It would probably be easier to run a 
#6 since it can be run of the surface.

How have you and your inspectors been interpreting this?

Thanks,

Drake 


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