[RE-wrenches] Supply side connection to a dedicated panel

[Mark Frye]

Well yes but, 690.64 (2) is titled and reads "Bus or Conductor Rating". The
"or" is important and the 120% requirement does not apply to the upstream
conductors, in this case.
 
In general, if the sudpanel of 225A where backfeed with the 120A of PV and
had a 150A breaker on its feeder from the main panel, the conductor between
the main panel and the sub need be rated only for the 150A feeder conductor.
 
The size of the feeder tap between the transfer switch lug and the new sub
panel needs to be evaluated differently.
 
I myself am a big fan of 240.21 (B), even when it comes to feeders with PV
on them. I guess some folks are not, but other than the expression of
opinion, I don't see anything to prohibits the use of downsized feeder taps
in PV circuits. I think most folks would go for a downsized conductor to
connect up the new subpanel, so long as it was located right next to the
transfer switch equipment.

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 Jason
Szumlanski
Sent: Tuesday, October 12, 2010 4:05 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Supply side connection to a dedicated panel


That sounds right, which means that the existing wiring between the service
disconnect and the transfer switch may also need to be evaluated since it
will now have sources available at both ends. The rule applies to all bus
bars and conductors "upstream" of the interconnection point  as I understand
it.

Jason Szumlanski
Fafco Solar
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