[RE-wrenches] Question

Brian Teitelbaum bteitelbaum at aeesolar.com
Thu Jun 15 17:04:08 PDT 2017


That complicates it a bit. If you have 200A coming in from the grid, and
another 200A coming in from the inverters (4 x 48A = 192A), you will need
to size the wire to the transfer switch for 400A. In a fault condition,
you could potentially see that much amperage on those wires before the
200A grid breaker trips (which will cause the grid-tie inverters to shut
down).

Brian Teitelbaum
AEE Solar

-----Original Message-----
From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
Behalf Of penobscotsolar at midmaine.com
Sent: Thursday, June 15, 2017 4:33 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Question

Sorry, 200 amp main breaker in a 400 amp rated panel.


> Hi Daryl,
>
> From your description, yes, if you are attaching to lugs connected to
> busses and then to the 400A main breaker, with no other overcurrent
> device between, you would have to size the wire for the 400A rating.
>
> Brian Teitelbaum
> AEE Solar
>
> -----Original Message-----
> From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org]
> On Behalf Of penobscotsolar at midmaine.com
> Sent: Thursday, June 15, 2017 4:10 PM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] Question
>
> I re-read and see that I need to clarify my earlier question. The 400
> amp,
> 120/208 panel has a main breaker that will be used for the utility
> input, coming in on 3/0 copper.  The four 60 amp breakers will be used
> because the four 10 kW inverters maximum ac output is 48 amps each (x
> 1.25 =60 amps ocpd). On the opposite end of the 400 amp panel there
> are main lugs which will be used to feed the generator transfer
> switch, essentially, because the inspector says we cannot put more
> than "two in, one out" on the gentran. These wires to the gentran are
> what I am wondering how best to size. Common sense tells me they
> should be rated the same as the main panel breaker from the utility. Is
this a correct assumption?
>
>
>> Esteemed wrenches,
>>    We're working often in the Bahamas and now that net metering is
>> approved there, the inspectors are far behind in their comprehension.
>> That said, we are currently required to combine the utility with the
>> PV in a main load center before going to the generator transfer
>> switch. I have a 400 amp rated load center with a 200 amp, 120/208
>> main breaker on it, as well as four 60 a, 3 pole breakers that will
>> be fed from four
>> 10 kw inverters. My question is, will it be necessary to use wire
>> rated at 400 amps or can I use wire rated for the main breaker? Thank
>> you for your input. It might be a stupid question, but I am stymied
>> here....it might just be the Lyme, not sure.....oh, and it's CEC 2015
>> down there, but I suspect it will align with NEC 2014.
>>
>> Thanks again,
>> Daryl DeJoy
>> NABCEP Certified PV
>> Penobscot Solar Design
>>
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