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

[Jason Szumlanski via RE-wrenches]

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@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@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.
>> ___
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Re: [RE-wrenches] Grid Tied Inverter back feed to Generator

[Dave Angelini Offgrid Solar via RE-wrenches]

Picture tells one alot also. You can't have 2 or more sources without 
isolation, batteries or not.  Cheers!


Dave Angelini Offgrid Solar
"we go where powerlines don't"
   [1]https://offgridsolar1.com/ [2]  [1]
e-mail  offgridso...@sti.net
text 209 813 0060

On 2023-12-01 4:16 pm, Jerry Shafer via RE-wrenches 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 
 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.
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Links:
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Re: [RE-wrenches] Grid Tied Inverter back feed to Generator

[Jerry Shafer via RE-wrenches]

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@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.
> ___
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Re: [RE-wrenches] Grid Tied Inverter back feed to Generator

[Eric Smiley via RE-wrenches]

 We were called to repair a system where this happened.
All the micro inverters were fried and so was the generator. It caused a
voltage rise that the monitoring system recorded at 348 V before it went
down, when the PV ran the generator as a motor.


*Eric Smiley,* Design Manager
e...@vecoop.ca
T: 250.703.6004 <+12507036004>
T: 888.386.0116 <+18883860116>
*VIRIDIANENERGY.CA *

* *


On Thu, 30 Nov 2023 at 17:20, Jeremy Rodriguez via RE-wrenches <
re-wrenches@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.
> ___
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Re: [RE-wrenches] Grid Tied Inverter back feed to Generator

[Dave Tedeyan via RE-wrenches]

Jeremy,

It is my understanding that if the generator wakes up the grid tied
inverter and loads are more than the solar then maybe nothing bad would
happen. Although I would never do that because you don't have any control
over the loads. And if the solar production is more than the loads, then
the excess energy feeds back to the generator and can break things. In
other words, move the solar interconnection to the line side of the
transfer switch so that there is no chance of the generator and solar
"seeing" each other.

Cheers,
Dave

On Thu, Nov 30, 2023 at 8:20 PM Jeremy Rodriguez via RE-wrenches <
re-wrenches@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.
> ___
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-- 
[image: Logo] 
Dave Tedeyan, P.E.
Owner | Sungineer Solar
p: he | him | his
a: 1653 Slaterville Rd. | Ithaca, NY 14850
w: www.sungineersolar.com 
c: (607) 270-0370
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[RE-wrenches] Grid Tied Inverter back feed to Generator

[Jeremy Rodriguez via RE-wrenches]

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. 
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