[RE-wrenches] Grid Tied Inverter back feed to Generator

[Jason Szumlanski]

AC coupling the Enphase IQ8 microinverters with a generator and no
batteries is a supported setup with their System Controller 2 or 3G. The
"Sunlight Only Backup" system in this configuration starts the generator
automatically during a grid outage, but generator power will only be used
if the loads exceed the PV inverter combined output. This is intended to
reduce fuel burn, presumably, and start up large loads. I'm not sure how
they deal with large loads dropping off, but the IQ8 responsiveness to load
changes is supposed to be lightning fast, so I assume they have that all
figured out. There are sizing ratio limits.

We have never installed a system like this (without batteries), and I can't
imagine a scenario where I think it would be worthwhile in a residential
setting unless there is a consistently moderate to high load during
daylight hours. I just don't think the reduction of fuel burn would be
substantial enough to justify the expense and complexity of the System
Controller. Standby generators often run near idle anyway around here
except when air conditioners cycle on and off. With pool pumps being so
efficient, and often left out of backup load panels anyway, there are not
many consistent loads in a house in a grid-outage scenario that would
benefit the homeowner by reducing fuel consumption substantially.
Unfortunately, it's hard to find ideal fuel burn figures for many
generators to do proper estimates.

So a question aside from "what happens" if you AC couple a generator with
PV is whether it's even worth it.

Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956


On Fri, Dec 1, 2023 at 7:16 PM Jerry Shafer via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Wrenches
> Without batteries uou do not want to do this, l have tested small
> generators to excite larger solar inverters to run constant loads but if
> the inverters out power the loads then the smoke comes out so not advisable
> But hey thats just a guy that has been in the business for many years.
> Fun times.
>
> On Thu, Nov 30, 2023, 5:20 PM Jeremy Rodriguez via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> Has anyone experienced a grid tie inverter back feed a whole house backup
>> generator after a utility outage?
>> What can happen ?
>>
>>
>> Jeremy Rodriguez
>> Solar Installation / Design
>> All Solar, Inc.
>> 1453 M St.
>> Penrose Colorado 81240
>>
>> Sent by Jeremy's iPhone. Sorry for typos and shorthand.
>> _______________________________________________
>> List sponsored by Redwood Alliance
>>
>> Pay optional member dues here: http://re-wrenches.org
>>
>> List Address: RE-wrenches at lists.re-wrenches.org
>>
>> Change listserver email address & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>
>> There are two list archives for searching. When one doesn't work, try the
>> other:
>> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/
>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>
>> List rules & etiquette:
>> http://www.re-wrenches.org/etiquette.htm
>>
>> Check out or update participant bios:
>> http://www.members.re-wrenches.org
>>
>> _______________________________________________
> List sponsored by Redwood Alliance
>
> Pay optional member dues here: http://re-wrenches.org
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Change listserver email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> There are two list archives for searching. When one doesn't work, try the
> other:
> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/
> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> http://www.re-wrenches.org/etiquette.htm
>
> Check out or update participant bios:
> http://www.members.re-wrenches.org
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20231202/b4143ad6/attachment.htm>