[RE-wrenches] Generator and Enphase

Jason Szumlanski Jason at fafcosolar.com
Sat Mar 26 15:04:04 PDT 2011


We've explored this strategy many times due to all of the whole house
and critical load generators in Florida. We've stayed away from the
contactor solution because of the potential for the NC contactor failing
to open, keeping the inverters "online" when transferred to generator
power. While unlikely, this is a possibility that must be considered.

 

The other issue presented here is that the inverters will shut down
every time the generator exercises.

 

The only sure-fire way seems to be wiring the inverter on the utility
side of the transfer switch, as Kent said.

 

Jason Szumlanski

Fafco Solar 

 

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Kent
Osterberg
Sent: Saturday, March 26, 2011 5:56 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Generator and Enphase

 

Mark,

I agree it is best to wire the inverters on the utility side of the
transfer switch. When that isn't easy, a normally closed contactor that
is opened by generator voltage, will isolate the inverters from the
generator and allow automatic return to utility operation when the
generator is off.

Kent Osterberg
Blue Mountain Solar



Mark Frye wrote: 

Eric,

 

I do not have direct experience with this but have been exploring the
issue for a project I am currently doing.

 

My response will be to take the trouble to interconnect the Enphase
inverters on the line side of the tranfer switch so that the inverters
can never be connected to the generator.

 

Here are the reasons why:

 

1 - Enphase states that any such application is considered an "off-grid"
application which voids their warrenty. As I am installing under the
California CSI program, I am required to provide a 10 year manufacture
equipment warranty so I cannot afford to install the inverters in a
dis-allowed manner.

 

2 - Enphase states that the waveform of the generator may be "clean"
enough such that the inverter may attempt to syncornize and connect to
it as if it were the utility. If this were to happen Enphase believes
the inverters will ruin the generator regulator before the generator
ruin the inverter. I don't want to be the one to run the experiment to
find out which would be which.

 

3 - I considered a contactor on the output of the inverters, such that
the inverters would isolated by a loss of line voltage, requiring some
form of reset. Ulitmately my customer agreed with me that this was an
undesirable constraint on the operation of an otherwise reliable
grid-tied system and it was not clear that this would satify the
warranty issue.

 
Mark Frye 
Berkeley Solar Electric Systems 
303 Redbud Way 
Nevada City,  CA 95959 
(530) 401-8024 
www.berkeleysolar.com <http://www.berkeleysolar.com/>   

 

 

________________________________

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Eric
Thomas
Sent: Saturday, March 26, 2011 2:09 PM
To: re-wrenches at lists.re-wrenches.org
Subject: [RE-wrenches] Generator and Enphase

I have a customer with a "30A Mechanically Interlocked Breaker" for
their generator feed at the main panel. My question is: If the home
power is transferred from utility to generator power, will the backfed
PV see the generator as grid power and sync up and produce? This is a
nice Honda Generator so the power should be fairly clean. Any
experiences are appreciated.

Take Care,


Eric Thomas
Solar Epiphany LLC
(206) 919-3014
www.solarepiphany.com



 
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