# Solar +20% rule and City of Palo Alto



## rexowner (Apr 12, 2008)

Per 690.64, it's generally possible have a back-fed breaker feeding from
the inverter into a panel.

According to Palo Alto:
http://www.cityofpaloalto.org/civica/filebank/blobdload.asp?BlobID=17784


> Center fed electrical services can not use the 120% rule per CEC 690.64 (B)(7)


I have not seen this interpretation elsewhere (CEC is just NEC2008 in this
case, I read the code and it is identical wording).

Does this make sense?

Given how common it is to have 200 Amp rated center-fed all-in-ones
or meter-mains with 200Amp mains installed for the last decade, this 
seems to be overly restrictive and against the intent of 690.64.

Has anyone else run into this in PA or any other jurisdiction and do you agree?


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## vida (Feb 21, 2012)

why does it say "center fed" in there? very curious. 
That section is 705.12 these days

I cant understand that as better, seems like it will make you do a lot more derating main breakers and such...


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## rexowner (Apr 12, 2008)

vida said:


> why does it say "center fed" in there? very curious.
> That section is 705.12 these days
> 
> I cant understand that as better, seems like it will make you do a lot more derating main breakers and such...


Thanks for the response. 

You are right it is 705.12 these days -I think Palo Altos is a little behind the
times.

I think it says "center fed" because the City likes to make things up which are
not in the Code. I have not heard "center fed" being an issue anywhere else
- if it were I'd have to rip out at least a couple of dozen installations, and
there are probably 10K's like that in California.


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## don_resqcapt19 (Jul 18, 2010)

The code rule requires the back fed breaker to be on the panel bus at the opposite end from where the main breaker is installed. See 690.64(B)(7). I assume by "center fed" they mean that one of the two breakers that supply the panel bus are not installed at the ends of the bus.


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## rexowner (Apr 12, 2008)

don_resqcapt19 said:


> I assume by "center fed" they mean that one of the two breakers that supply the panel bus are not installed at the ends of the bus.


Thanks for the response, it's been a pretty quiet thread.

I would say about 3/4 of new single family residential construction in this area
gets an all-in one (usually 20 spaces/40circuits, 10 above and 10 below the main)
or a meter-main (8/16, half above and half below the main) that looks like this:








which I would call "center fed". These cans typically have a 200Amp breaker
preinstalled in the center and a 200 amp bus.

Saying that the 20% rule can't be applied with a backfed breaker installed
at the end of the bus is tantamount to saying solar can't be installed without
a service swap.

IMO, "opposite" means the end of the bus, even if the utility main is in the
center. I think if the code was meant to preclude center-fed mains, it
should have been explicit, but was not. This jurisdiction is the only time
I have seen "center" enter into it, which is why I was curious as to 
whether anyone else has seen that interpretation.


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## ElectricJoeNJ (Feb 24, 2011)

rexowner said:


> Saying that the 20% rule can't be applied with a backfed breaker installed
> at the end of the bus is tantamount to saying solar can't be installed without
> a service swap.


that's not accurate. There's always the option of doing a tap on the load side of the meter.


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## rexowner (Apr 12, 2008)

ElectricJoeNJ said:


> that's not accurate. There's always the option of doing a tap on the load side of the meter.


Yes, that's true, would involve redoing the service, but indeed you are correct.


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## ElectricJoeNJ (Feb 24, 2011)

rexowner said:


> Yes, that's true, would involve redoing the service, but indeed you are correct.


How does that involve redoing the service?? Tap inside the main panel with insulbite taps. Go to a new CB disco. Done.


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## McClary’s Electrical (Feb 21, 2009)

Not sure about your meter main shown, but I can get panels with 250 amp buss and 200 amp main that helps those percentages in your favor.


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## rexowner (Apr 12, 2008)

ElectricJoeNJ said:


> How does that involve redoing the service?? Tap inside the main panel with insulbite taps. Go to a new CB disco. Done.


Got ya. Most of the services here have the meter and main in one box as
a manufactured assembly.

Googled "insulbite" and the first hit was your post in another thread
in January. Mind posting a reference?


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## ElectricJoeNJ (Feb 24, 2011)

http://www.drillspot.com/products/676730/burndy_bipc3504_0_mechanical_hot_line_tap_single_connector


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## vida (Feb 21, 2012)

http://www.greentechmedia.com/articles/read/Feed-in-Tariff-for-PV-in-Palo-Alto-Ca-Imminent/

might want to stay flexible in that city, cause you will find more work there soon.

BTW- you can also do a load calc and downsize the main breaker to 175 or even 150 many times.


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## C10/Inspector (Feb 15, 2013)

*690.64(b)(7)*

A Little late on the input here, but look here on page 27.
http://osfm.fire.ca.gov/pdf/firemarshal/California_Solar_Permitting_Guidebook.pdf


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## uconduit (Jun 6, 2012)

A little off topic, but does Palo Alto Power Company allow new installations of high leg-delta? Advantages/Disadvantages?


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