Meter main/Auto transfer switch for Generator

smileyboy

Member
I have a customer with a meter main that was installed about a year ago.
He now would like a 18k generator hooked up.
Is there a way to use his current setup for a Automatic transfer switch? This is only my 4th generator install and I haven't done one with combo like this.

Thanks IMG_0115 (2).jpeg
 

ppsh

Member
Location
CA
Occupation
Electrician
Easiest possible meter main to do an ATS. Lug block off of the main breaker, pipe into the ATS and land that on your utility terminals. Extend the subfeed that comes into the meter main, and land that on your load terminals.
 

smileyboy

Member
Thanks for the response! I don’t completely understand. I need to visualize it. I’ll be back at the job Monday and hopefully that will clear it up.


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Todd0x1

Senior Member
Location
CA
Install a subfeed block in the combo panel, feed ATS with it. Install new subpanel connected to load side of ATS and reroute all circuits to it.
 

smileyboy

Member
Install a subfeed block in the combo panel, feed ATS with it. Install new subpanel connected to load side of ATS and reroute all circuits to it.
Seems like a lot of unnecessary work for this project. The panel is not on the other side of the wall.. the ATS can handle the entire home


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kwired

Electron manager
Location
NE Nebraska
Easiest possible meter main to do an ATS. Lug block off of the main breaker, pipe into the ATS and land that on your utility terminals. Extend the subfeed that comes into the meter main, and land that on your load terminals.
Thanks for the response! I don’t completely understand. I need to visualize it. I’ll be back at the job Monday and hopefully that will clear it up.


Sent from my iPhone using Tapatalk
If all you have is the meter and the one main you intercept the feeder to the subpanel with the ATS. If you have other loads out of the meter main those won't be able to run on the generator unless you move them to the sub panel.

Your photo looks like you just have the one main with what we can see though.
 

smileyboy

Member
If all you have is the meter and the one main you intercept the feeder to the subpanel with the ATS. If you have other loads out of the meter main those won't be able to run on the generator unless you move them to the sub panel.

Your photo looks like you just have the one main with what we can see though.
Intercepting the sub panel feed makes sense. What about the utility side? The utility wire goes from the ATS to where? When the meter main are split it’s easy to place the utility wires.


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Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
You can't modify the meter/main to intercept the feed from the meter to the load/service side.
Only legal way that I've come up with is to feed the ATS off the meter/main, then to the house panel that has the branch circuits. Of course, the ATS is now not the service equipment and the bond must be removed and neutrals and grounds separated.
I did this on a new install and was no problem. If existing, more trouble since you would have to re-do the house panel feed or add another subpanel.
 

Todd0x1

Senior Member
Location
CA
Seems like a lot of unnecessary work for this project. The panel is not on the other side of the wall.. the ATS can handle the entire home


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Thats the only way to legally do it. You can't rewire the factory wiring in the meter/main combo panel to connect the ATS.
 

Todd0x1

Senior Member
Location
CA

Would this work?


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Sort of. In your combo meter main the wires going into the 200A breaker likely come from the meter.. The buss is on the load side of the breaker. This is why I suggested the subfeed block since there is nowhere in that meter main combo for you to land the conductors supplying the ATS.
 

smileyboy

Member
Sort of. In your combo meter main the wires going into the 200A breaker likely come from the meter.. The buss is on the load side of the breaker. This is why I suggested the subfeed block since there is nowhere in that meter main combo for you to land the conductors supplying the ATS.


Thank you!!!! I get it now.


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GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Thats the only way to legally do it. You can't rewire the factory wiring in the meter/main combo panel to connect the ATS.
In many meter main combos the "wiring" from the load side lugs to the line side of the main breaker on the panel side is rigid metal bussing from end to end. No way to intercept it except by sawing it and making holes to bolt on lugs. Clearly not supported by manufacturer.
The variation that you have puts the main breaker in a backfeed configuration to the panel bus. This may use actual wire, but still might not be considered as field modifiable. But since there are no load breakers you do have options on the load side of the main breaker.
Also, if your POCO accepts or offers them there are full ATS devices or connection adapters which mount between the meter socket and the meter.
I do not know whether any of them support generator starting or load shedding though.
 

kwired

Electron manager
Location
NE Nebraska
Intercepting the sub panel feed makes sense. What about the utility side? The utility wire goes from the ATS to where? When the meter main are split it’s easy to place the utility wires.


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To the feeder breaker.

If this is a service rated transfer switch, you would need to remove any bonding jumper, ungrounded conductors don't matter, you just have an extra circuit breaker in your installation that sort of isn't needed. If not a service rated transfer switch then you still need an overcurrent device ahead of the switch anyway and it is perfect for your situation.

"Utility side" means the side supplied by the utility and not necessarily that it must be the actual service conductors.

Some are not marked utility and generator but rather normal and standby or something similar.
 
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