Generac transfer switch to a sub panel?

[infinkc]

was wondering if I will run into any issues with running a Generac 200a Transfer switch to a sub panel.

So my main is on one side of the house, the sub is in the garage. The sub has all the breakers for the lights and outlets, so that is what I want to backup.

Have a 400a main pictured.

I was going to connect off the top 200a breaker input(from meter, new wires) to the input of the transfer switch and back to the breaker from the switch.

My concern is that sub is not near the generator, is there any concern? Or am I ok since the wiring is already gauged per that length.

 

[wyliesdiesels]

where do you want to put the ATS?

how far away will the generator be?

 

[infinkc]

where do you want to put the ATS?

how far away will the generator be?

The main is flush mounted, I could either mount on the wall next to it, or was thinking to mount it behind the panel as it’s a closet wall that I have access to. I would then only need to run the wires out to the generator. (Picture of the back of the panel before the walls went up)

The generator will be right near the panel and the ats. Maybe 12ft total of wire back to the ats.

 

[wyliesdiesels]

The ATS should go on the outside so emergency personnel can have access to it.

You will need to unbond the neutral bar and add a ground bar in the xfer sw since it wont be the main service panel.

 

[infinkc]

The ATS should go on the outside so emergency personnel can have access to it.

You will need to unbond the neutral and add a ground bar since it wont be the main service panel.

Ah, didn’t think about that this would become a new service main for the sub panel. Guess outside it has to go. Going to be much more fun now trying to get the wires out the wall since the panel is flush. Thanks!

No concern that the generator has to feed a longer run? As typically they feed a main that’s right there also.

 

[mm08822]

I would do it this way:
Mount ATS in closet so you can ****** into the backside of the existing meter/main enclosure from the back of the ATS enclosure. (Upper left corner of ATS = Upper right corner of metermain.)

This ****** let's you connect from the loadside of the top 200a cb to the ATS.
Move the SER from the metermain enclosure into the top of the ATS enclosure.

Then run your gen output into ATS along with control cable.

ATS is a sub-panel so it needs a 4wire feed and no bonding of neutral to ground in it.

Gen cb would have to be shutoff if working on 200a subpanel as well as 200a cb in metermain.

 

[mm08822]

What size gen ?
How far is subpanel from metermain?
How far is gen from ATS?

 

[wyliesdiesels]

Ah, didn’t think about that this would become a new service main for the sub panel. Guess outside it has to go. Going to be much more fun now trying to get the wires out the wall since the panel is flush. Thanks!

No concern that the generator has to feed a longer run? As typically they feed a main that’s right there also.

except it wont be a main service panel since you are connecting it to the load side of a breaker in the combination meter main...

if its just receptacles and lights i doubt VD would be an issue.

 

[wyliesdiesels]

I would do it this way:
Mount ATS in closet so you can ****** into the backside of the existing meter/main enclosure from the back of the ATS enclosure. (Upper left corner of ATS = Upper right corner of metermain.)

This ****** let's you connect from the loadside of the top 200a cb to the ATS.
Move the SER from the metermain enclosure into the top of the ATS enclosure.

Then run your gen output into ATS along with control cable.

ATS is a sub-panel so it needs a 4wire feed and no bonding of neutral to ground in it.

Gen cb would have to be shutoff if working on 200a subpanel as well as 200a cb in metermain.

I doubt the AHJ will allow it on the inside since panel may not be accessible in an emergency and shutting off breaker in meter main could turn on the generator and thus have power still feeding portions of the house

 

[The Cobbler]

shutting off breaker in meter main could turn on the generator and thus have power still feeding portions of the house

interesting point that I hadn't thought of. I guess emergency services wouldn't want to turn off the gas supply?

 

[mm08822]

The cb in the xfer switch only turns off grid power. That would make the gen run.

Need to go to gen and turn off there. Or the gas as it's another concern.

Most of the xfer switches i have installed are inside next to the original main panel.

This is one reason why gens now require an external estop without opening the gen enclosure.

 

[mm08822]

Also why decals are required at the meter informing of the presence of a gen and it's location.

 

[wyliesdiesels]

The cb in the xfer switch only turns off grid power. That would make the gen run.

Need to go to gen and turn off there. Or the gas as it's another concern.

Most of the xfer switches i have installed are inside next to the original main panel.

This is one reason why gens now require an external estop without opening the gen enclosure.

so when he turns off the feeding breaker in the main service panel, signaling a power outage to the ATS it wont turn on the generator?

 

[mm08822]

It will turn on the gen as I stated.

 

[wyliesdiesels]

It will turn on the gen as I stated.

oh you said breaker in xfer switch. i was referring to feeding breaker in main service panel...

 

[mm08822]

oh you said breaker in xfer switch. i was referring to feeding breaker in main service panel...

If the OP "rewires" the top cb so it is fed from the xfer switch and not directly from meter, it would act as a disconnect to the sub-panel.
The gen would still run but power can't get past the open 200a cb in meter/main.
I doubt the AHJ would pass that type of field modification.
FD would not trust that cb hearing the gen running. I'm certain they would shut down the gen. They don't have time to f around and maybe not even the correct knowledge.

 

[wyliesdiesels]

If the OP "rewires" the top cb so it is fed from the xfer switch and not directly from meter, it would act as a disconnect to the sub-panel.
The gen would still run but power can't get past the open 200a cb in meter/main.
I doubt the AHJ would pass that type of field modification.
FD would not trust that cb hearing the gen running. I'm certain they would shut down the gen. They don't have time to f around and maybe not even the correct knowledge.

yeah violating the listing of the panel... and like you said AHJ probably wont like it

 

[tarmy]

This is set up just like OP is talking about as it relates to feeding a 200a sub. I have a 400a main panel at the street with a 200a sub on the house that this transfer switch feeds. There is a separate 200a sub in the shop. The generator only feeds the ATS that feeds house sub panel. As others noted this is set up for exterior access. The generator is 400 or so feet from the ATS.

 

[mm08822]

How did that pass with ~4' height?

 

[infinkc]

If the OP "rewires" the top cb so it is fed from the xfer switch and not directly from meter, it would act as a disconnect to the sub-panel.
The gen would still run but power can't get past the open 200a cb in meter/main.
I doubt the AHJ would pass that type of field modification.
FD would not trust that cb hearing the gen running. I'm certain they would shut down the gen. They don't have time to f around and maybe not even the correct knowledge.

Bit confused now, So is the correct way to wire it:
1) keep the 200a in the main fed by the meter.
Output of the 200a feeds the transfer switch 200a breaker.
Output of the transfer switch to feed to the sub

Or
2)connect meter to transfer switch 200a breaker.
Output of transfer switch feeds the 200a main breaker that feeds the sub.

#2 seems the correct way to do it, as there is a way to disconnect power to the sub using the main panel breaker. But your are saying it’s wrong? Otherwise there is no breaker to the sub if the generator is on.

 

[infinkc]

What size gen ?
How far is subpanel from metermain?
How far is gen from ATS?

16kw, just for lights, recepts. No hvac, gas appliances.
Sub to main is probably 50-60ft(wire length)
Gen to ats would be 8-12 ft away(wire length)

 

[mm08822]

Bit confused now, So is the correct way to wire it:
1) keep the 200a in the main fed by the meter.
Output of the 200a feeds the transfer switch 200a breaker.
Output of the transfer switch to feed to the sub

Or
2)connect meter to transfer switch 200a breaker.
Output of transfer switch feeds the 200a main breaker that feeds the sub.

#2 seems the correct way to do it, as there is a way to disconnect power to the sub using the main panel breaker. But your are saying it’s wrong? Otherwise there is no breaker to the sub if the generator is on.

#1 is the correct way. Gen has cb in it protecting conductors back to xfer switch.
60 or 70A cb?

 

[Norcal]

The ATS should go on the outside so emergency personnel can have access to it.

You will need to unbond the neutral and add a ground bar since it wont be the main service panel.

Not possible in that meter/main the neutral is factory bonded, most are listed as for use as service equipment only.

 

[wyliesdiesels]

Not possible in that meter/main the neutral is factory bonded, most are listed as for use as service equipment only.

my unbonding comment was talking about the xfer sw NOT the meter main

 

[infinkc]

#1 is the correct way. Gen has cb in it protecting conductors back to xfer switch.
60 or 70A cb?

Forgot it had one, just checked its a 70a. thanks for the feedback!

 

[reader2580]

The AHJ didn't have an issue with me mounting the ATS inside the house. I never thought about firefighters cutting the power from the generator. They could open the front panel of generator and turn off that that breaker. I am pretty sure I installed the generator under NEC 2014, but I believe load shedding was required under 2014 NEC. The AHJ never said anything about load shedding, but I have the generator powering only a subset of circuits which may mean I don't need load shedding.

I have the NEC 2020 required emergency disconnect next to the meter, but didn't think about the generator. (I replaced my meter base and load center in 2020 and wanted to do the emergency disconnect in case I was required to have it in the future.)

 

[mm08822]

The AHJ didn't have an issue with me mounting the ATS inside the house. I never thought about firefighters cutting the power from the generator. They could open the front panel of generator and turn off that that breaker. I am pretty sure I installed the generator under NEC 2014, but I believe load shedding was required under 2014 NEC. The AHJ never said anything about load shedding, but I have the generator powering only a subset of circuits which may mean I don't need load shedding.

I have the NEC 2020 required emergency disconnect next to the meter, but didn't think about the generator. (I replaced my meter base and load center in 2020 and wanted to do the emergency disconnect in case I was required to have it in the future.)

HSB Gens require the meter or exterior disconnect location to be labeled as to the presence of a gen and its location. Newer units require an estop on the gen exterior for rapid shutdown.

 

[infinkc]

@mm08822 @reader2580 @Norcal @wyliesdiesels

OK, this is what i am going to do:

1)Mount the ATS inside behind the Main panel, will have a short 2" ****** to connect the two.
2)Will pull the wires going to the Sub and bring those into the ATS output.
3)Run new wire from the 200a main breaker to the ATS Input.
4)New ground and Neutral wire from main to ATS.
5) Ground and Neutral in ATS to be unbonded.
6) Come out the bottom of the ATS with 2" conduit out the wall and to the Generator, inside will be the main line and trigger wires (per Generac they can be in the same conduit)
7)Properly label Main panel for ATS location and area of disconnect on the Generator.

My only concern is the wires going to the sub might not be long enough to make the connection in the ATS, what is the correct way to splice this like 12" longer. I assume its allowed as its within the sub panel.

Anything I am missing?

 

[mm08822]

2" to the gen is overkill. 1.5" is fine.

If the conductors in the ser are too short but the cable jacket makes it into the ats, just use **** splices and add enough conductor to reach landing points.

If ser is too short to reach ats, consider a splice box in attic and add new ser down into ats. Locate splice box in a comfortable location to work on it.