[RE-wrenches] Generator and Enphase

Jason Szumlanski Jason at fafcosolar.com
Sun Mar 27 11:43:21 PDT 2011


Yes, each situation is different. Very rarely do we find ourselves
saying, "hey, this is just like the Jones/Smith job."

 

The only thing I would comment on is that in the case of a whole house
generator, there would not be a "non-backed up loads" line on the
drawing. All loads would be on the transfer switch and there is no
choice but to do a service side connection.

 

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: Sunday, March 27, 2011 2:37 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Generator and Enphase

 

Larry,

Situations vary so much that this might not be very useful. But here you
go. The attached sketch shows how we recently connected a customer that
had a backup generator and transfer switch that wasn't service rated.
There were nice gutters existing from the original install so accessing
points to tap conductors wasn't difficult. We could have connected the
inverters to the non-backed upped loads panel instead, but the utility
requires an accessible disconnect by the meter so it was more convenient
to just get into the gutter.

Kent Osterberg
Blue Mountain Solar



wirewiz at gmail.com wrote: 

Kent, Jason, or anyone else 

 

Would you a have a simple one-line you could share for wiring the
inverter on the utility side of the transfer switch? 

 

Thank you.

 

Larry Liesner

Wirewiz

Westport, CT

Phone: 203-644-2404

Fax: 203-557-0556

wirewiz at gmail.com

www.wire-wiz.com

 

 

 

On Mar 26, 2011, at 6:04 PM, Jason Szumlanski wrote:





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/>  

 

 

 
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