# Generator Interlock with solar panels



## WronGun (Oct 18, 2013)

Has Anyone had any installations like this ?

So far what I’ve gathered is the solar controller may be able to determine the difference between utility and gen power if not a contractor may be required 


Sent from my iPhone using Tapatalk


----------



## HackWork (Oct 2, 2009)

No go.

This is where you need a transfer panel. Even if you make one yourself by installing a normal subpanel and install an interlock on the main breaker of the subpanel and then move the essential circuits over to it.

The solar needs to be on the PoCo side of the transfer switch (which is the interlock if you instal one).


----------



## HackWork (Oct 2, 2009)

My above post is assuming that your solar system is backfeeding a breaker. If the solar is connected to the service entrance conductors via a line side tap, then it is fine to install an interlock the normal way since the main breaker will isolate them.


----------



## dmxtothemax (Jun 15, 2010)

QUOTE - [ So far what I’ve gathered is the solar controller may be able to determine the difference between utility and gen power ]


YES ! 

You are correct, the invertors can tell if they are connected to either the grid or to an generator.

Back feeding a generator just doesn't work !


----------



## WronGun (Oct 18, 2013)

HackWork said:


> My above post is assuming that your solar system is backfeeding a breaker. If the solar is connected to the service entrance conductors via a line side tap, then it is fine to install an interlock the normal way since the main breaker will isolate them.




It’s not back feeding the main panel 

The meter socket has a Disconnect main breaker and the solar feeds into it 


Sent from my iPhone using Tapatalk


----------



## HackWork (Oct 2, 2009)

Where, exactly, does the solar feed the house system?

A back fed breaker after the main? 

Somewhere else?

Is there a panel inside that you can install the interlock on, isolating both the utility and the solar from the generator breaker and branch circuits?


----------



## WronGun (Oct 18, 2013)

There is no breaker at the main panel for solar I only have pictures the customer sent me. 

Just Trying to get familiar with this before I go look in person. 

The panel only has 2 DP breakers 40A oven and 30A AC..

From the picture it goes to the meter socket and how solar exactly ties in I will have this answer when I go look closer 


Sent from my iPhone using Tapatalk


----------



## HackWork (Oct 2, 2009)

Basically, you need to keep the solar on the same side of the interlock as the utility power, this way when you switch over the interlock both the utility and solar are isolated from the house electrical system and generator.


----------



## mitch65 (Mar 26, 2015)

What Hack said. Xfer switch between your meter box disconnect and the main panel, when utility and solar fail, Xfer isolates them and panel gets power from gen.


----------



## HackWork (Oct 2, 2009)

What happens around here that I see often is the solar backfeeding the panel via a branch circuit breaker.

In that situation, you can't just install an interlock in the panel because the solar will still be feeding the house and backfeeding the generator, and vice versa.


----------



## nrp3 (Jan 24, 2009)

Looks like the solar ties into the meter main. If the panel doesn’t have a main then you’ll likely have to add one or change the panel to one that has one.


----------



## WronGun (Oct 18, 2013)

nrp3 said:


> Looks like the solar ties into the meter main. If the panel doesn’t have a main then you’ll likely have to add one or change the panel to one that has one.




Ya I will verify this but from the looks of exterior and panel Pictures I have the solar is at the meter main. 

I will need to add a main breaker to the panel 


Sent from my iPhone using Tapatalk


----------



## WronGun (Oct 18, 2013)

The panels tap the service conductors and don’t go inside to the panel










Sent from my iPhone using Tapatalk


----------



## WronGun (Oct 18, 2013)

Not familiar with solar setups. This is new to me.

How does this even work? Technically there are 2 power sources feeding the panel on the same lines. 


Sent from my iPhone using Tapatalk


----------



## HackWork (Oct 2, 2009)

FWIW, those aren't the service conductors. Those are the load side of the main breaker, which means they are feeders. 

If you add a main breaker to the panel inside, you can install an interlock on it and be compliant. The solar will be on the utility side of the interlocked breaker, which is what you want.


----------



## HackWork (Oct 2, 2009)

WronGun said:


> Not familiar with solar setups. This is new to me.
> 
> How does this even work? Technically there are 2 power sources feeding the panel on the same lines.
> 
> ...


Yes, that's pretty much it. Two power sources meshed together by the inverter. The solar in that house and all the millions of other houses backfeed into the grid and help power it.


----------



## JoeSparky (Mar 25, 2010)

Sorry to bump an old thread, but this one fits. Just looked at this situation today on a Siemens panel. Solar feed is a 2 pole breaker. I think this might work with 2 interlocks. Should be able to relocate the solar feed to ckts 2 and 4 and put the generator breaker in ckts 1 and 3. ecsbpk01 on the generator/solar breakers and ecsbpk03 with the normal tin snipping on the right side of it. Should work if the interlocks don't interfere with each other. Anybody tried this yet?


----------



## wpelectric94 (8 mo ago)

How about installing an electrically interlocked contactor on the normally closed side coil tapped off the generator breaker when generator has power activates the contactor opens the contacts and disconnect the solar


----------



## joe-nwt (Mar 28, 2019)

If you lose a coil/fuse, then what?


----------



## backstay (Feb 3, 2011)

This was 2018 and a SolarEdge inverter. I wouldn’t trust it to stay off line with a generator.

Just for future reference, there are other inverters that have wiring terminals for the grid, a generator and an output. Outback Radian, and FXR inverters. Magnum MS, SMA Sunny Island, are just a few.


----------



## nrp3 (Jan 24, 2009)

Any of the installs I've been working on, I've had the solar moved to the utility side of the transfer switch so there's no issues. Most of these involved the same style inverter.


----------



## dragonara (Jul 3, 2018)

Maybe this should be its own thread, but since more and more customers are wanting solar, gen transfer switch and the new requirement for an exterior disco: what are your preferred meter /main/ transfer/distribution setups? And why.
The desire to separate some priority loads for battery backup also seems to complicate things.


----------



## backstay (Feb 3, 2011)

Here is with an Outback Radian.













https://www.outbackpower.com/downloads/documents/wiring_diagram/single_radian_grid_interactive_load-side_tap_oneline_rev_3.pdf


----------



## Almost Retired (Sep 14, 2021)

dragonara said:


> Maybe this should be its own thread, but since more and more customers are wanting solar, gen transfer switch and the new requirement for an exterior disco: what are your preferred meter /main/ transfer/distribution setups? And why.
> The desire to separate some priority loads for battery backup also seems to complicate things.


there is a forum for solar etc. 








Alternative Energy Forum


Solar, Wind, and other forms of alternate energy discussed here.




www.electriciantalk.com


----------



## Almost Retired (Sep 14, 2021)

@Dennis Alwon should this thread be moved to alternative energy ??


----------



## nrp3 (Jan 24, 2009)

Alternative is becoming normal, and I think these kinds of issues, adding a generator, adding solar and or batteries, where there is already a generator, is well, becoming more common. Not sure whether it would be missed if put in a separate place.


----------



## wpelectric94 (8 mo ago)

Just like all the other equipment if something fails in the inverter what stops it from from powering the house at least you're somewhat protected and you can hear it when the generator kicks in


----------



## wpelectric94 (8 mo ago)

Just like all the other equipment if something fails in the inverter what stops it from from powering the house at least you're somewhat protected and you can hear it when the generator


wpelectric94 said:


> Just like all the other equipment if something fails in the inverter what stops it from from powering the house at least you're somewhat protected and you can hear it when the generator kicks in


Also if you lose a fuse or the breaker shuts off the generator is not powering the house therefore it's not an issue but I do see if the coil fails you will still have a problem but again that's like every other electrical piece of equipment nothing lasts forever


----------



## wpelectric94 (8 mo ago)

The best way and fool proof is to install interlocking relay circuit but more expensive where if utility power on solar is in when generator power is on solar is out.


----------

