Backfeeding a 200 amp panel with an Outback 3048 [RE-wrenches]

[Ray Walters]

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Here's some crazy ideas:
Could Outback separate Grid AC IN (for loads and battery charging at 
60amps) and then have an AC OUT to Grid  that could be sized much 
smaller just to accomodate the max. array size and therefore get around 
120% bus limit?
1) Is this possible,
2) are there any other grid tie/ battery backup inverters with this 
ability (two AC outs),
or 3) once again am I just dreaming?

Crazy Idea 2: could we do this with 2 inverters? For instance, one 
inverter only setup for sell back, and the other only set for backup 
loads. (Clunky? yes.)

Crazy Idea 3: on the 20% rule:  that's at  240 vac, so if you used  a 40 
amp double pole breaker you would still be within 120% on a 200 A 
service, then you could use a transformer to step down to a single 
inverter for its full pass through capability. (might actually fly)

We are looking at this same problem, only worsened with 100 amp main 
service panels here (20 amp breaker max). It seems some exception needs 
to be created  for Gridtie/ Power backup in future codes. Consider an 
Outback inverter with pass through/ back up to half the house really 
needs the full 60 amp breaker, but it might only have a few hundred 
watts of PV for sell back (less than 10 amps backfeed). As soon as you 
remove the array, you have no problem (its only a load). As soon as you 
add one measly PV panel, the project is in the junk bin. The bussbar 
rating consideration should be based not on the breaker, but the max. 
possible backfeed the system can provide. (the array size)

Feel free to shoot my theories full of holes,

Ray Walters




William Miller wrote:

>
>
> Andrew:
>
> I have a "Point of Connection" spread sheet on my web site at:
>
> http://mpandc.com/resources/resources.html
>
> It may be helpful.
>
> William Miller
>
>
>
> At 02:41 PM 10/11/2006, you wrote:
>
>> Andrew,
>> No, 175A. If it's a 200A panel, you can't put a main breaker larger than
>> that in it. 200A is the busbar rating of the panel - but check the 
>> label:
>> you might have a panel with a 200A main breaker and a higher busbar 
>> rating -
>> then you're OK.
>>
>> Check out NEC 690.64b(2). It's the sum of all sources that can't 
>> exceed 120%
>> of the busbar rating of the panel. In your case, 120% of 200A is 
>> 240A. With
>> a 200A main breaker, you can also have a 40A inverter feed. If you 
>> put in a
>> 60A, that would be 130%. Put in a 175A main breaker, and 175 + 60 = 
>> 235A,
>> which is within 120%.
>>
>> Allan
>
>
>
> - - - -
>
>


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