Hi Garrison- The dedicated breaker referred to in 705.12(D)(1) means they do not want the inverters plugged into branch breakers. One (and only one) inverter into each pole of a 3-pole breaker seems safer and better than 3 individual breakers, and seems to fit the definition of "dedicated" breaker.
I don't know that you can even find single-pole 277 Vac breakers....
DonB
-------- Original Message --------
Message: 6
Date: Fri, 4 Apr 2014 08:01:00 -0500
From: "Garrison Riegel" <garri...@solarserviceinc.com>
To: <re-wrenches@lists.re-wrenches.org>
Subject: Re: [RE-wrenches] Three Inverters, One Disconnect?
Message-ID: <828201cf5005$edd065b0$c9713110$@solarserviceinc.com>
Content-Type: text/plain; charset="utf-8"
Hi Don,
Thank you for your reply. Good idea on the single 480V inverter, but multiple subarrays at different tilts/orientations and strings lengths make that impractical unfortunately.
It also seems like a good idea to use a single 3-pole breaker to prevent phase imbalance, but I thought each inverter required a dedicated breaker as per 705.12(D)(1). Thoughts?
Thanks,
Garrison
From: d...@energysolarnow.com [mailto:d...@energysolarnow.com]
Sent: Thursday, April 03, 2014 1:55 PM
To: re-wrenches@lists.re-wrenches.org; Garrison Riegel
Subject: RE: [RE-wrenches] Three Inverters, One Disconnect?
With single phase 240 each inverter output is two poles; but since you are using 277 each inverter output is between one pole and neutral, so you could indeed use a 3-pole disconnect since the neutrals are not switched.
A 3-pole breaker is usually used with 3-phase systems, but since there are 3 separate inverters it is legal to use 3 single pole breakers provided you get them into separate phase poles. However, there would be a phase imbalance if one breaker tripped and the others were still sourcing current, so it's better to use a 3-pole breaker here.
But rather than go to all the work of wiring 3 separate 3.6 kW inverters, why not just use the PowerOne 10.0 or 12.0 kW 3-phase inverters? This would be less expensive and would need just one conduit run for input and output.
Don Barch
Energy Solar
-------- Original Message --------
----------------------------------------------------------------------
Message: 1
Date: Wed, 2 Apr 2014 17:20:36 -0500
From: "Garrison Riegel" <garri...@solarserviceinc.com ><mailto:garri...@solarserviceinc.com> >
To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org ><mailto:re-wrenches@lists.re-wrenches.org> >
Subject: [RE-wrenches] Three Inverters, One Disconnect?
Message-ID: <817a01cf4ec1$c5d8ad00$518a0700$@solarserviceinc.com ><http://solarserviceinc.com> >
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Hello Wrenches,
On an upcoming project we are interconnecting (3) Power-One, ahem, ABB PVI
3.6 inverters to a 3Ph 277/480V service. Each inverter output is 16A at
277V, 1Ph. Is it code compliant to run the single phase output of each
inverter to a single pole of a 3-pole [utility required] AC disconnect
before landing at each 1-pole 20A breaker in the main panel? It would be
great to avoid an inverter subpanel and 3-pole breaker in the MDP if
possible.
Thanks for your thoughts.
Garrison
Garrison Riegel
Project Manager | <http://www.solarserviceinc.com ><http://solarserviceinc.com> /> Solar Service Inc
[p] 847-677-0950 | <mailto:garri...@solarserviceinc.com>
garri...@solarserviceinc.com <mailto:garri...@solarserviceinc.com>
NABCEP Certified PV Installation ProfessionalT
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