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 <[email protected]>
To: [email protected]
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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