200 amp transfer switch on a 100 amp service

[Not Sure]

Can I use a 200 amp transfer switch on a 100 amp service?
I guess what I'm asking is does the 200 amp breaker in the ATS become the main and therefore I would have to run 4/0 AL to a 100 amp panel? Which becomes a sub panel.
Some guys are telling me no, that it is just a switch not actually the main and the service size stays #2 cause both the generator and the panel are 100 amp.
The generator was package bought with the transfer 200 came with 16kw generac.
Please advise.
Thanks, Not Sure

 

[GoldDigger]

Since the ATS becomes the service disconnect, the OCPD closely associated with it becomes the service OCPD, and must be smaller than or equal the nominal service size. This OCPD theoretically protects the service conductors as well as the downstream conductors. For that reason it cannot be Code compliant if it is too large.
Can you change the OCPD inside the 200A ATS? If not, can you place a service OCPD before the ATS?

 

[Not Sure]

Well they are saying is it really the service disconnect if you turn off the 200 amp breaker...the generator fires and the panel still has power from the generator?

 

[GoldDigger]

As long as the ATS is service rated, I suppose that you could argue that it is placed before the actual service disconnect. But when the ATS switches the original service disconnect is no longer in the circuit.
The exact determination may in practice lie with your particular AHJ.

 

[LarryFine]

The first breaker is the main disco, but distances may allow use of tap rules.

 

[qcroanoke]

Since the ATS becomes the service disconnect, the OCPD closely associated with it becomes the service OCPD, and must be smaller than or equal the nominal service size. This OCPD theoretically protects the service conductors as well as the downstream conductors. For that reason it cannot be Code compliant if it is too large.
Can you change the OCPD inside the 200A ATS? If not, can you place a service OCPD before the ATS?

I agree, a 100 amp over current device in front of the ats connected to normal would work

 

[Not Sure]

So if I use the tap rules I could run 4/0

 

[Not Sure]

Sorry didn't finish run 4/0 from the meter to the 200 amp ats breaker out of there #2 to the service panel as long as is within 25'?

 

[augie47]

 

[infinity]

Sorry didn't finish run 4/0 from the meter to the 200 amp ats breaker out of there #2 to the service panel as long as is within 25'?

If you run the conductors on the outside of the building the tap conductors can be any length and are not limited to 25'

 

[Not Sure]

Thank you I appreciate the advice

 

[sparky1118]

Can I use a 200 amp transfer switch on a 100 amp service?
I guess what I'm asking is does the 200 amp breaker in the ATS become the main and therefore I would have to run 4/0 AL to a 100 amp panel? Which becomes a sub panel.
Some guys are telling me no, that it is just a switch not actually the main and the service size stays #2 cause both the generator and the panel are 100 amp.
The generator was package bought with the transfer 200 came with 16kw generac.
Please advise.
Thanks, Not Sure

I did the same thing at my house. Inspector allowed it since the conductors are protected by the 100 amp breaker in the electrical panel. The 200 amp breaker in the transfer switch is just used as a disco.

Sent from my SM-G998U using Tapatalk

 

[fjm]

I have a similar question..I have a 100amp service with a 22kw (100A) generator and 200A ATS. I installed a 100A Main breaker then to the 200A ATS with #4. From Utility load side in ATS again ran #4 to the panel, then from generator to ATS ran #2. After I was finishing looking at it in panic I swapped the #4 to #3 (only cause it was what I had available).

Do you think I would have been ok with #4? Undersized ....