[RE-wrenches] off grid PV connected to generator

SunHarvest eric at harvesthesun.com
Tue Jan 15 13:50:16 PST 2013


I'm a bit confused by this thread and am looking for some clarity. To that 
end here's an example of a recent installation we completed (under the 
direction of a licensed electrician, not me (praise the Lord)):

Grid & Genset feed Main Panel (genny on ATS) ---> Main panel feeding 
subpanel ---> subpanel is point of connection for our PV array with Enphase.

My understanding is that the inverters will look for an "infinite grid" and 
sensing none when the grid goes down but instead sensing the genset power, 
the inverters will not turn on.

So, we should have tied the PV system to the main panel, that's what I'm 
reading from the conversation. This would have been completely cost 
prohibitive due to trench length. Now should we advise the customer to 
manually open the PV breakers in the subpanel to be safe? This is what I'm 
reading from the conversation.

Further, I recently installed a GVFX for a customer. I'm hearing from 
certain sources that the grid-tied line of inverters from Outback are not 
designed to interface with a generator. Really??

I was told by Outback to install a transfer switch line/supply side of the 
inverter; that this was the only way to interface the genny with the 
inverter; that the AC Hot In could come from grid or a genset. And indeed, 
this is the only way I can figure out how to get the genny to charge the 
batteries when the grid goes down. But then again, I don't have the 
extensive electrical background that allows me to think outside the box as 
often as I would like...that's why I'm posing my query here for the pros. In 
this Outback install I have to again advise the homeowner to open the PV 
breaker to the inverter during generator operation, right? Even though he 
has a modest 600W (STC) array and an 8.5kW Kohler genset. Hardly the 
opportunity for solar to feed back to the genny under the most sunny and 
cool of days. I'm more concerned with the Enphase install.

The Xantrex SW series inverters are fully capable of operating on-grid or 
off-grid with a genset. So do those inverters automatically disconnect the 
PV when the genny auto-starts? And with the Outback, is the Mate supposed to 
do the same (as long as the genny is operated by the auto-start and not a 
transfer switch)?

Eric
SunHarvest




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