[RE-wrenches] One renewable disconnect.

[John Wadley]

Darryl
    The solar backfeed is about 85A, the existing 3-phase panel is about 300A and 
drives 4 AC units and parking lights and the existing split-phase panel is about 
200A and drives office equipment.  I think I'd rather drive the 20kW directly to 
the three phase to alleviate the AC loads than the smaller split-phase loads.  Also, 
I'm going by an article I read saying you should try not to unbalance a 3-phase 
by more than about 6kW.  The transformer might be able to handle it, but the utility
has not been very cooperative about providing me with specifications.

     I'm not sure I completely followed your second comment.  It sounds like a lot 
of switches, though.  I'm leaning towards Jeff Oldham's advice and just integrating 
the 10A of wind at the solar AC sub-panel.  It is plenty big enough and won't 
drive up the cost.

Thanks to you and Jeff for taking time to offer suggestions.

Best Regards,
John Wadley


________________________________
From: Darryl Thayer daryl_solar at yahoo.com
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Wed Mar  2 15:59:20 PST 2011
Subject: [RE-wrenches] One renewable disconnect.


I hope i do not muddy the water here.  if you have 3 phase delta, usually the 
single phase transformer is larger, can you do the solar in split phase?  


Also staying with the 3 phase, why not use a three pole service rated switch to 
Line side tap, and use two poles for the single phase and the third pole for the 
high leg.  After the 3 pole switch, use a 2 pole switch for the wind turbine 
(breaker in a box) , and a three pole sw in a box for the 3 phase solar.   .  





________________________________
From: John Wadley <wadleyjk at hotmail.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Wed, March 2, 2011 3:36:19 PM
Subject: [RE-wrenches] One renewable disconnect.

Wrenches,
      I am designing a system with both wind and solar backfeed and I'm having 
an issue with the utility.  They say we need to have a single renewable 
disconnect switch before the grid backfeed.  The solar is designed to backfeed 
3-phase through a meter, then a fused AC disconnect to the line-side to avoid 
upsizing the MDP.  The wind inverter output is 120/240V split-phase (10A) which 
I had planned to do load-side backfeed through a wind meter with a seperate AC 
disconnect since it was so small.  To meet the single renewable disconnect 
requirement, I'm thinking I may need to backfeed the wind on the load-side to 
one of the three phases.  I guess my question is can I use a single 5 pole fused 
AC disconnect to control both with one switch handle or is that an NEC violation 
wrt to merging separate systems within the same conduit?  Or, should I keep them 
in separate switch boxes with some kind of gang handle?  I have a 3-phase 
aggregation panel for the solar inverters (6 total, 2 per phase, 240 delta), but 
if I integrate the wind there in order to simplify the AC disconnect issue, the 
solar meter will register both solar and wind production.  What is the best 
practice in this situation?

Thanks,
John Wadley, MSEE, PE
NABCEP Certified Solar PV Installer (TM)
Wadley Engineering
214-557-3841

 		 	   		  
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