[RE-wrenches] Three Inverters, One Disconnect?

[Garrison Riegel]

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: don at energysolarnow.com [mailto:don at energysolarnow.com] 
Sent: Thursday, April 03, 2014 1:55 PM
To: re-wrenches at 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 --------
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Message: 1
Date: Wed, 2 Apr 2014 17:20:36 -0500
From: "Garrison Riegel" <garrison at solarserviceinc.com <mailto:garrison at solarserviceinc.com> >
To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org <mailto:re-wrenches at 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:garrison at solarserviceinc.com>
garrison at solarserviceinc.com <mailto:garrison at solarserviceinc.com> 



NABCEP Certified PV Installation ProfessionalT




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