[RE-wrenches] Generator backfeeding enphase?

Chris Mason cometenergysystems at gmail.com
Tue Oct 20 09:25:57 PDT 2015


He's wrong. Any inverter system will try to raise the voltage of the
system, that's how grid tied inverters feed power to the load. With the
utility grid, there is no issue as the inverter cannot move the voltage any
significant amount (unless there is a high resistance point). With a
generator which is also trying to feed the same load, as the inverter's
output power comes close to the load, the voltage will rise and the
generator's AVR will get confused. It will reduce the excitation to the
alternator and will likely start to motor if the inverter's power output
exceed the load. The generator can shut down if the the system voltage
exceeds the high voltage setpoint, and other bad things can happen such as
damage to the AVR and stator windings. There's no real way to know what
will happen. In many cases where the load exceeds the inverter output,
nothing bad happens, but it's a crap shoot.

On Tue, Oct 20, 2015 at 12:01 PM, Howie Michaelson <howie at suncatchervt.com>
wrote:

> 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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-- 
Chris Mason
NABCEP Certified Solar PV Installer™
Solar Design Engineer
Generac Generators Industrial technician

www.cometsolar.com <http://www.cometenergysystems.com>
264.235.5670
869.662.5670
Skype: netconcepts
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