[RE-wrenches] Generator and Enphase

wirewiz at gmail.com wirewiz at gmail.com
Sun Mar 27 12:20:36 PDT 2011 

Kent,

Situations vary but this one line helps a lot, thanks.

So,  "To PV System" would go to the output of a grid tie inverter and "To Backed Up Loads" would go to the AC IN (transfer switch) of a battery inverter. 

I have been going to homes with existing 100A gen/utility ATS and wondering if I could keep it as is and be able to add a grid tie battery backup to it (using same backup loads). This schematic would work in that situation as well but wouldn't have the "To Non-Backed UP Loads" tap.


Larry Liesner
Wirewiz
Westport, CT
Phone: 203-644-2404
Fax: 203-557-0556
wirewiz at gmail.com
www.wire-wiz.com



On Mar 27, 2011, at 2:36 PM, Kent Osterberg wrote:

> 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 
>>>  
>>>  
>>> 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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