ATS switch

[GerryB]

Been a while since I posted. I have a question, can a 200 amp ATS be used with a 100 amp service, Installed as normal after the meter and ahead of the panel, with the existing #2 conductors. The way I understand it the 100 amp panel breaker is still the OC protection. The genny also has a 100 amp breaker.

 

[augie47]

IMO, the conductor size and the ATS utility main would need to match (100 amp breaker #2, 200 #2/0 etc).
If the load side to the existing panel would quaolify under the tap rule you could employ that for the load conductors (if you keep the 200 amp main)

 

[garbo]

Appears to be okay but I always check with my inspector or the AHJ. At the large hospital/ research center that I retired from they had over 70 ATS' S. For some reason they were in love with 1200 & 1600 amp ATS'S. Think they had over 15,000 amps of ATS'S on a generator ( emergency power ) on a 5000 switchboard and load never went over 1800 amps. They seemed to waste a lot of money by using say 1200 amp switch that only feed a 400 amp panel and load never went over 125 amps. If customer has the money great going with closed transition ATS due to no blip during transfers and can perform yearly & triannual PM on them during regular working hours. They had a super critical lab that was was feed by dual service and its own 13,200 volt 2 Meg generator along with several ATS'S and 480 volt panels that could be transferred via Kirk keys.

 

[Rock86]

Hmm... Well, I would think it would be okay. I can't think of or find a direct code violation unless it has an OCP. If it is just the switch and it is rated for 200A, i'd think you would be allowed for ranges up to 200A. I'm going to look up a little more info because of Augie's post.

 

[infinity]

Been a while since I posted. I have a question, can a 200 amp ATS be used with a 100 amp service, Installed as normal after the meter and ahead of the panel, with the existing #2 conductors. The way I understand it the 100 amp panel breaker is still the OC protection. The genny also has a 100 amp breaker.

Will this AT switch be the service disconnect?

 

[GerryB]

Will this AT switch be the service disconnect?

It will be the first means of disconnect, grounding will originate there and the existing 100 amp main breaker panel will have grounds and neutrals isolated. The EI doesn't like it but is asking the state inspector about it. I'm thinking it's ok. We are on 2017, but I understand 2020 requires a Main disconnect outside 1&2 family homes but that it doesn't have to be the overcurrent protection, just a disco for the firemen. So this is similar.

 

[infinity]

It will be the first means of disconnect, grounding will originate there and the existing 100 amp main breaker panel will have grounds and neutrals isolated. The EI doesn't like it but is asking the state inspector about it. I'm thinking it's ok. We are on 2017, but I understand 2020 requires a Main disconnect outside 1&2 family homes but that it doesn't have to be the overcurrent protection, just a disco for the firemen. So this is similar.

Take a look at 230.90(A). Since it's the service disconnect the service entrance conductors will need to be 200 amps.

 

[don_resqcapt19]

Where is the main panel located in relation to the ATS? If the ATS is the service disconnect, then the service OCPD must be located in the ATS or "located immediately adjacent thereto". 230.91

If the service is actually a 100 amp service, I don't see any reason that you can't use 100 amp wire with the 200 amp ATS, assuming that the installation complies with 230.91.

 

[GerryB]

Where is the main panel located in relation to the ATS? If the ATS is the service disconnect, then the service OCPD must be located in the ATS or "located immediately adjacent thereto". 230.91

If the service is actually a 100 amp service, I don't see any reason that you can't use 100 amp wire with the 200 amp ATS, assuming that the installation complies with 230.91.

That is a good reference. They are located next to each other. I will see if we get a response from the state.