point of connection [RE-wrenches]

[William Miller]

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Larry:

There is no inherent limitation on the supply-side option.  As you have 
correctly surmised, the 2 SB5000 inverters create an output that exceeds 
the allowance in 690.64B.  The breaker rating is not the factor, the Max AC 
amps rating (20.8 AAC) from the manufacturer is.

Section 690.64A allows a supply side connection.  This point of connection 
must be between the meter and the service disconnecting means.  This is not 
always easily accomplished.  When accomplished, we use the tap rule 
(430.28).  When designing this, choose a breaker panel to combine your 
inverter AC feeds that has a large enough bus rating and connect it to the 
tap with over-current protection that is less than the bus rating.  This 
gives you the allowance to connect your inverters.

Our web site has a spreadsheet you can use to check your 
calculations:  http://mpandc.com/resources/resources.html

Thanks,

William Miller

PS:  I am not sure what you mean by a "feed through" panel.  Could you 
describe this device?

WM

At 10:12 AM 5/2/2008, you wrote:

>Wrenches,
>
>We are doing an installation with 2 Sunny Boy 5000 inverters each
>requiring a 30 amp 2 pole breaker.  The closest point of
>interconnection is outside the house on the supply side of the main
>service disconnect near the customer side of the utility meter.
>According to 690.64B on the load side we are limited to 120% of the
>busbar rating, which means we could not put 2- 30 amp backfeed
>breakers in the main 200 amp service panel.  But 690.64A does not
>state a limitation  of 120% .  So we are considering a 200 amp feed
>through panel, also recommended by our local electrical inspector,
>and then putting our 2-30 amp 2 pole breakers in this feed thru
>panel. Anyone have any comments on this method? What other methods
>are people using to make a supply side interconnection?
>
>Larry Brown
>Sun Mountain


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