[RE-wrenches] Feeding 160A 3PH to a 800A/800A Main Service

[Kirk]

The 120% rule applies to both commercial and residential from the 2008 code on.

Kirk Herander
VSE

On Jun 17, 2013, at 2:58 PM, Allan Sindelar <allan at positiveenergysolar.com> wrote:

> Pekka,
> I believe that the 120% rule is only for residential application. Unless it's changed (and I don't do commercial any more, so I may be all wet here) you're limited to 100% on commercial       applications. The assumption is that a commercial service may already be running at or close to full ampacity, while residential is unlikely ever to do so.
> Allan
> 
> Allan Sindelar
> Allan at positiveenergysolar.com
> NABCEP Certified PV Installation Professional 
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> Founder and Chief Technology Officer
> Positive Energy, Inc., a Certified B CorporationTM
> 3209 Richards Lane
> Santa Fe, New Mexico 87507
> 505 424-1112 office 780-2738 cell
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>  
> On 6/17/2013 11:33 AM, Pekka Laine wrote:
>> Dear Fellow Wrenches,
>> 
>> We have a small 50kW 120/208V commercial job with five 9kW 3PH inverters, each outputting max. 25A.  We are landing those into a dedicated load center with five 40A breakers. Doing the math, 5 x 25A x 1.25 = 156.25A, we would need a 160A breaker.  This also equals to the maximum we can backfeed into a 800A/800A Main Service on the load side according to the "120%" rule.
>> 
>> The problem now is that we cannot locate any kind of 160A breaker or even a 160A fuse for a AC disconnect.
>> 
>> Has anybody ever done this without doing a "line-side tap?" It is hard to believe that there wouldn't be an existing solution to landing maximum PV into a 800A service. Are we missing something?
>> 
>> Any good ideas or comments would be appreciated.
>> 
>> Sincerely,
>> 
>> Pekka Laine
>> 
>> President
>> Photon Solar Power Inc.
>> www.PhotonSolarPower.com
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