Multiple services with one ATS

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Talley1013

Member
Location
Houston, TX
Hey fellas. I hope everyone had a great turkey day. I have a question about a xfer switch install.

The gen is 50kv and will supply power to a home(200a service) and garage/office(100a service). Is there any way that I can feed both services with one transfer switch and still be code compliant? I dont think that it is possible but I know the homeowner would prefer to only purchase one ATS so I figured I would check it out with you guys. I haven't been able to find any code reference that directly addresses this situation. I appreciate the help and thanks in advance for helping me learn something new.

ET
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Hey fellas. I hope everyone had a great turkey day. I have a question about a xfer switch install.

The gen is 50kv and will supply power to a home(200a service) and garage/office(100a service). Is there any way that I can feed both services with one transfer switch and still be code compliant? I dont think that it is possible but I know the homeowner would prefer to only purchase one ATS so I figured I would check it out with you guys. I haven't been able to find any code reference that directly addresses this situation. I appreciate the help and thanks in advance for helping me learn something new.

ET
If these are are 2 separate services you are going to need 2 transfer switches. One generator feeding 2 switches for 2 separate services is OK, but in this case you will need to set the optional standby system up as an SDS with switched neutral transfer switches. If you don't do it this way you will have the neutrals of 2 seperate services tied together. This will rule out a resi grade transfer switch like a Generac as they are not available with switched neutral. You'll need to go to Onan, Asco, Generac(commercial) or similar supplier for a switched neutral Xfer switch.
 

Talley1013

Member
Location
Houston, TX
If these are are 2 separate services you are going to need 2 transfer switches. One generator feeding 2 switches for 2 separate services is OK, but in this case you will need to set the optional standby system up as an SDS with switched neutral transfer switches. If you don't do it this way you will have the neutrals of 2 seperate services tied together. This will rule out a resi grade transfer switch like a Generac as they are not available with switched neutral. You'll need to go to Onan, Asco, Generac(commercial) or similar supplier for a switched neutral Xfer switch.
Thanks. I hadn't thought about the neutral/SDS situation. It makes perfect sense.

How would you feed the 2 xfer switches? Feeder from the gen to a tap block in gutter/j-box then from the tap block to the 2 switches? There shouldn't be any problem complying with the requirements for feeder taps.

Thanks again for you input

ET
 

ceb58

Senior Member
Location
Raeford, NC
Hey fellas. I hope everyone had a great turkey day. I have a question about a xfer switch install.

The gen is 50kv and will supply power to a home(200a service) and garage/office(100a service). Is there any way that I can feed both services with one transfer switch and still be code compliant? I dont think that it is possible but I know the homeowner would prefer to only purchase one ATS so I figured I would check it out with you guys. I haven't been able to find any code reference that directly addresses this situation. I appreciate the help and thanks in advance for helping me learn something new.

ET
Is it actually 2 services or is it 1 service feeding two buildings on the same property?
 

hillbilly1

Senior Member
Location
Atlanta,Ga
I've done that before with a 40 KW, instead of using a tap block, I used a 200 amp MB feed through panel, (with 6-8 breaker spaces) feed the 200 amp ats with the feed thru lugs, put a 100 amp breaker in the panel to feed the 100 amp ats. Of course your 50 KW may have a 225 amp main, in which that will not work.
 

Speshulk

Senior Member
Location
NY
If these are are 2 separate services you are going to need 2 transfer switches. One generator feeding 2 switches for 2 separate services is OK, but in this case you will need to set the optional standby system up as an SDS with switched neutral transfer switches. If you don't do it this way you will have the neutrals of 2 seperate services tied together. This will rule out a resi grade transfer switch like a Generac as they are not available with switched neutral. You'll need to go to Onan, Asco, Generac(commercial) or similar supplier for a switched neutral Xfer switch.
Help me out here. Why is it ok for two separate services to be connected to the same neutral when fed from the utility, but not from a generator?
 

Talley1013

Member
Location
Houston, TX
That's a great idea hillbilly.

I know that most generators we install have a fused disco before the ats. Is that a code req? Do I have to have a fused disco before the ats?
 

Talley1013

Member
Location
Houston, TX
That's a great idea hillbilly.

I know that most generators we install have a fused disco before the ats. Is that a code req? Do I have to have a fused disco before the ats?
Sorry, I wasn't very clear with this post. I meant to ask if the gen feeders are required to have a fused disco before the ats. Like I said, typically this is how we do them at work but a lot of the installs are way over designed. This little project is for my mom&stepdad so I want to keep cost down as much as possible.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Most generators already have a circuit breaker for overload and over current protection, your locality maybe requiring a disconnect on the outside of the generator if they consider the internal one not easily accessible. Does not have to be fused though, it can be non fused or even a molded case switch.
 

Talley1013

Member
Location
Houston, TX
Most generators already have a circuit breaker for overload and over current protection, your locality maybe requiring a disconnect on the outside of the generator if they consider the internal one not easily accessible. Does not have to be fused though, it can be non fused or even a molded case switch.
Thats what I thought. Thanks. The gen does have an ocpd. I think we have a pretty good idea of what we want to do when he is ready to make this happen.
 
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