Single Standby Generator for Two Meters?

[titan1021]

I have client that owns a small building that was originally two suites. He is interested in having a standby generator installed, as we are in Ca and will be having intermittent power outage for the next 5-10yrs. The building has single service drop that goes into a gutter then to two utility owned meters.
One panel being 125a and the second 100a. This is single phase 120/240. I plan to install a 22kw generator but I am not to sure how to go about powering both panels with the single generator. Hoping someone can give me a little advice or point me in the right direction.
Do they make transfer switches for this type of scenario?

Thanks

 

[LarryFine]

If you keep the two separate meters, you'll need two transfer switches, typically controlled in a master/slave arrangement.

 

[hillbilly1]

You will also need both to be a three pole transfer switch because you will need to switch the neutral, otherwise, you will have parallel currents on the panel neutrals. Also you will need to make the generator a sds. If Generac still controls the transfer switch via generator, (six wire control) one of the switches will be the master, and the other the slave. (As Larry said) The generator utility sense and charger circuit on the slave cannot be connected, but the transfer relay can. If it is two wire start, then both can be independent, but really wouldn’t matter because both would lose utility at the same time.

 

[texie]

Looks to me like you will have to rebuild the service since you have meter/mains.

 

[hillbilly1]

If that is a single main on the left, you should be ok, but looks like multiple mains on the right, so it would have to be converted to a single main with a sub panel after the transfer switch for the other circuits.

 

[titan1021]

If that is a single main on the left, you should be ok, but looks like multiple mains on the right, so it would have to be converted to a single main with a sub panel after the transfer switch for the other circuits.

Both are Mains 125a each. Based on the comments it seems like it would be best to consolidate to one 200a main them install a single transfer switch. Tried contacting Generac and Kohler and both companies want to send other companies out for an estimate, which isn't helpful as I want to do the job for this long time client.

 

[Strombea]

We do this often and to simplify things, just order the 22kw generac, the kit will come with one ATS and you will need to order the second one seperate, On 1 ATS you will use all 6 wires and on the second one you will just use (194 +12v) and (23 Transfer) in parallel with the other ATS.

I have never needed the 3 pole transfer switch but it is definitely a good idea,... My brain is trying to wrap around the reasoning. If 1 main tripped due to over current and the power was still on to the other main then you would have generator neutral and utility neutral on the same line in gutter, but when power goes out it is all derived and phased from generator so i think it should be fine.

 

[titan1021]

We do this often and to simplify things, just order the 22kw generac, the kit will come with one ATS and you will need to order the second one seperate, On 1 ATS you will use all 6 wires and on the second one you will just use (194 +12v) and (23 Transfer) in parallel with the other ATS.

I have never needed the 3 pole transfer switch but it is definitely a good idea,... My brain is trying to wrap around the reasoning. If 1 main tripped due to over current and the power was still on to the other main then you would have generator neutral and utility neutral on the same line in gutter, but when power goes out it is all derived and phased from generator so i think it should be fine.

Thanks. Just what I needed.

 

[hillbilly1]

We do this often and to simplify things, just order the 22kw generac, the kit will come with one ATS and you will need to order the second one seperate, On 1 ATS you will use all 6 wires and on the second one you will just use (194 +12v) and (23 Transfer) in parallel with the other ATS.

I have never needed the 3 pole transfer switch but it is definitely a good idea,... My brain is trying to wrap around the reasoning. If 1 main tripped due to over current and the power was still on to the other main then you would have generator neutral and utility neutral on the same line in gutter, but when power goes out it is all derived and phased from generator so i think it should be fine.

The problem is, the neutrals from service "A" and service "B" will be parralelled at both transferswitches. So when on utility the neutral current will be split for both services. Not really a big problem (other than code violation) unless the two services are vastly different in size, say one is an 800 amp, while the other is a 100 amp, and the neutral load is high (not likely though)

 

[Strombea]

That makes sense, thank you for clarifying. I never thought of that luckily I haven't done one that is not like for like(both 200 amp mostly)

 

[hillbilly1]

We do this often and to simplify things, just order the 22kw generac, the kit will come with one ATS and you will need to order the second one seperate, On 1 ATS you will use all 6 wires and on the second one you will just use (194 +12v) and (23 Transfer) in parallel with the other ATS.

I have never needed the 3 pole transfer switch but it is definitely a good idea,... My brain is trying to wrap around the reasoning. If 1 main tripped due to over current and the power was still on to the other main then you would have generator neutral and utility neutral on the same line in gutter, but when power goes out it is all derived and phased from generator so i think it should be fine.

I haven’t put in a Generac for years now, so I didn’t know if they still used the six wire control, but you are exactly right on how the controls should wire if they still do that.