[RE-wrenches] Service Panel Bus Rating

Mac Lewis maclewis1 at gmail.com
Mon Dec 1 06:07:42 PST 2014


Hi Wayne,

I think they are simply asking for the amp rating of the bussing (usually
available on the service panel sticker, or in spec sheet), and the amp
rating of the main breaker.  You will need to show that you can comply with
the 120% rule for a load side connection.

Thanks

On Sun, Nov 30, 2014 at 7:29 PM, Allan Sindelar <allan at sindelarsolar.com>
wrote:

>  Wayne,
> I don't think that you are correct. The bus rating of a 200A service panel
> may or may not be 200A, but it's not simply 120% of the panel's rating.
>
> The original 120% rule was premised on the fact that in residential
> applications, panelboards (and thus busbars) were seldom if ever run at
> full ampacity, and thus a 20% "negative load" of a PV system was unlikely
> to ever cause overloading and overheating of the busbar. You'll note that
> this was originally allowed only in residential applications; commercial
> buildings were expected to likely run at or near capacity.
>
> I think you'll need to get the actual busbar rating from the manufacturer.
> Allan
>
>  *Allan Sindelar*
> allan at sindelarsolar.com
> NABCEP Certified PV Installation Professional
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> Founder (Retired), Positive Energy, Inc.
> *505 780-2738 <505%20780-2738> cell*
>
>
>  On 11/30/2014 4:45 PM, Wayne Irwin wrote:
>
> Hello Wrenches,
>
> Hope you all had a nice Thanksgiving.
>
> I have an AHJ asking for the service panel buss rating and the service
> panel buss protection rating.
>
> Am I correct to assume that the rating is the service panels designated
> rating x 1.2% (ie 200A x 1.2 = 240)?
> and that the buss protection is the combined input breakers? 200 Main
> breaker + 40A solar back feed = 240A?
>
> Given that there are many different size panels (150A and 200A) that share
> the same bus, I have a difficult time believing this to be true.
>
> If there is any designated signage or data sheets specific to the service
> panel, where might I find this?
> I have looked at Schnider but have not been able to find anything specific.
>
> Thanks,
>
>
> Wayne Irwin,
> President
> License #CVC56695
> State Licensed Solar Contractor
> Pure Energy Solar International Inc.
>  Wayne at PureEnergySolar.com <PureEnergySolar at hotmail.com>
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-- 



Mac Lewis

*"Yo solo sé que no sé nada." -Sócrates*
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