I'd consider a fused disconnect on the line side of the 200 amp main.
The wires on the load side are treated just as a bussbar. 690.64 (which
is now 705.12) reads conductor or bussbar.
You could use a 100% duty rated 40 amp fused disconnect, and get up to
9600 watts through on the load side, but a regular disconnect is going
to be limited by 690.8 to 80% of 40 amps, (7.7 KW inverter rated output
x 125% = 40 amps)
Since the subpanels have 125 A bussbars, but only 60 amp mains, you
could add there without further penalty, but the bottom line is: you're
not going to get 10KW on the load side and be code compliant.
Ray Walters
On 12/22/2011 11:34 AM, Pekka Laine wrote:
All,
We have been contracted to install a 10kW-ac system into a 45-year old house that
has no main service breaker panel, only a 200A fused main switch (Zinsco). There
are five 125 A rated sub-panels throughout the house, some of which have 50A&
60A breakers in them. I have been told that we are not limited to 40 A max. PV as
per 690.64 (B) since there is no main bussbar. I have three questions:
1. Can we land 60A into one of these existing sub-panels
2. If not, how would you recommend "tapping" in the old 200 A fused main switch
wires?
3. What do you think is the maximum amperage of PV that can be backfed in to
this service?
Any other recommendations welcome.
Respectfully,
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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