[RE-wrenches] Generators and Grid-tie Systems

[Drake Chamberlin]

I was recently told by SMA that in the event that 
the inverters did connect to generator output, 
and the load was less than the inverter output, 
that the voltage would rise and the inverters 
would fall off line.  A year or so before I'd 
been told by another SMA representative that 
generator circuit boards had been fried by inverter backfeed.

It would  be very good to get to the bottom of this one.

At 10:10 PM 3/1/2010, you wrote:
>Hi folks:
>     (Eric, by 'directly to the utility grid' I do mean with a breaker)
>    Jason and  Allen, I agree with what you are 
> saying, in theory, but in practice, it is not 
> always possible.  I am installing a generator 
> in a couple of weeks for a customer with an 
> existing 9 KW array.   The property's main 
> service is located at a separate building from 
> the house, loads, and solar.  The main panel 
> feeds 200 Amps to the main residence and 200 
> Amps to a barn building (300 ft away)  The barn 
> building has the array at it, and also the well 
> pump, which needs to be backed up by the 
> generator.  This requires us to either dig a 
> 300' trench or just leave the system in 
> auto.  We will be utilizing a 200A Automatic 
> Transfer Switch, but we will not be able to 
> place the generator into Auto mode.  The 
> customer understands the situation, and said 
> that he would leave the genny in 'manual' start 
> mode.  I feed good about the situation, will 
> disable the auto-start system, and will provide competent labelling.
>
>Nick Soleil
>Project Manager
>Advanced Alternative Energy Solutions, LLC
>PO Box 657
>Petaluma, CA 94953
>Cell: 707-321-2937
>Office: 707-789-9537
>Fax: 707-769-9037
>
>
>
>From: Jason Szumlanski <Jason at fafcosolar.com>
>To: re-wrenches at lists.re-wrenches.org
>Sent: Mon, March 1, 2010 3:50:23 PM
>Subject: Re: [RE-wrenches] Generators and Grid-tie Systems
>
>This is déjà vu.
>
>I would say that the only safe and "correct" way 
>is to connect the PV inverter output on the line 
>side of the transfer switch. If you are on the 
>generator side of the xfer switch, you are 
>asking for trouble. The only other choice would 
>be to use a contactor to ensure PV disconnection 
>when the grid is down - then you could tap the 
>PV on the load side of the transfer switch.
>
>And to answer Eric's #1 question in the original 
>post, you may not need to resize/replace the 
>panel if you follow this approach. We go with a 
>line side tap in this scenario unless there is a 
>compelling reason to do otherwise.
>
>Jason Szumlanski
>Fafco Solar
><http://fafcosolar.com>http://fafcosolar.com


Drake Chamberlin
Athens Electric
OH License 44810
CO License 3773
NABCEP TM  Certified PV Installer
Office - 740-448-7328
Mobile - 740-856-9648  
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