You can't go wrong with a new "solar-ready" service panel. You can tell the
customer that, in addition to enabling a larger solar system, it is a safety
upgrade.
Otherwise you're going to have to backfeed one of these subpanels or the one of
the 100A mains inside the house.
Do the mains in #2 have their own breakers, or are they pass-through lugs? Or
one of each (which is what I've commonly seen before). As I've argued
previously, if there's a main C/B on both these points, that isolates the 200A
main disconnect and the load-side feeder from it. If both of the "mains" are
100A busses with 100A main C/Bs, then you can only backfeed 20A on each (even
if you're tying in on one of the other subpanels). Which would would limit you
to 40A overall for the system -- less than the 60A you want. If one of the
"mains" is a pass-through lug, then that moves the problem to the subpanel that
it is feeding.
Jeffrey Q.
________________________________
From: Pekka Laine <pe...@photonsolarpower.com>
To: re-wrenches@lists.re-wrenches.org
Sent: Sunday, December 25, 2011 1:46 AM
Subject: Re: [RE-wrenches] Landing into a sub-panel without a main service
Thank you for all the great interest and the comments on this topic. Here are
some more details on this project:
1. 200 A fused Zinsco Main Switch at the service entrance (45 years old)
2. Inside the house Square D Split-bus "Main" panel with two 100 “Mains” fed by
1/0 wire from the outside 200A Main fused switch
3. Next to it Murray 100/125A Sub-panel (Newer, some damage)
4. Outside Zinsco 125A Sub-panel
5. In the pool room 125A Sub-panel
6. In the garage Murray 125 A Sub-panel (newer, looks OK)
The utility is SDG&E, so no line or load side taps are usually allowed. On
another project, we have previously replaced a similar type fused main switch
with a Eaton Solar Ready Loadcenter with 225A rated buss and 200A main breaker
in order to be able to backfeed max. 70 A of PV. I am leaning towards doing the
same on this one....
In this case, I will recommend the customer to upgrade/replace the old Square D
split bus panel and items 3 & 4. as well. Any other suggestions are welcome.
Happy Holidays!
Pekka Laine
President
Photon Solar Power Inc.
www.PhotonSolarPower.com
Cell. 760-556-8170
Toll Free 888-SUN-ACDC
CA Lic. #933648
NABCEP Certified PV Installer # 032611-174
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