[RE-wrenches] Generator backfeeding enphase?

[Daniel Young]

I still run under the assumption that if the solar generation ever exceeds building demand in these situations, the building voltage will spike up to the high voltage cutout of the inverter (unless the generator has the capability to try to “motor” to bring the voltage back down), then the voltage will return to normal. The system will wait 5 min (as if there were a grid fault, then return), then attempt to re-connect. If the solar generation is still in excess of the demand, the inverters will cycle again. This essentially is short cycling the inverters. Or if the generator circuitry is trying too hard to pull the voltage back down, it could damage the generator, but it depends on the size/type of genny. Like has been said already, it’s a crap shoot.

 

Will it kill the inverters quickly…..I doubt it. Will they have voided the warranty….I’d almost guarantee it.

 

The new Envoy S has some more advanced features though, so It may be able to monitor production vs demand and force the array to throttle back to prevent this from happening. I’m not familiar enough with the product to say one way or the other. I imagine it would have to be capable of reacting very quickly though to prevent issues (say, if your electric clothes dryer finished it’s cycle, changing you from needing 2kW of generator to supplement PV to all of a sudden having 2kw too much PV). 

 

With Regards,

 

Daniel Young, 

NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Howie Michaelson
Sent: Tuesday, October 20, 2015 12:01 PM
To: RE-wrenches
Subject: [RE-wrenches] Generator backfeeding enphase?

 

Does anyone think that there is no issue with having enphase potentially backfeeding a backup generator? We almost always will tie in upstream of a generator transfer switch, but a competitor is telling clients with an enphase system there is no concern. Am I missing something?

Thanks,
Howie
Howie Michaelson
NABCEP Certified Solar PV Installer™

Catamount Solar
Renewable Energy Systems Sales and Service
VT Solar Electric Incentive Partner
http://www.CatamountSolar.com
802-272-0004

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