[RE-wrenches] Generators and Grid-tie Systems

[Nick Soleil]

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

>>> Hi Eric:
    Did you notice my e-mail on this subject last week?  I was hoping that someone would have some new, more concrete information on this subject, but I guess the old story still applies.  Here is the basic run down.
    The inverters will likely see the generator as utility power, especially if it is a decent quality generator, with a clean wave form.  The inverters will connect to the generator and back-feed the power into the generator's alternator, causing heat and generator failure.  The solar will burn up the alternator.  I have heard that this has occurred before.
    The only way to prevent this is to connect the solar directly to the utility power (not through the >generator's backed-up emergency load center.)  
>    If you must connect the solar through the generator's emergency load center, then the generator must >not be placed into "Auto," but must instead be in "manual."  The customer must be clear that the solar >breakers must be turned off before the generator is turned on.  This probably should include signage >which makes this clear to the customer.

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