100 amp service

Location
Wisconsin
Occupation
Electrician
can i install a 200 amp service rated transfer switch ahead of main panel feeding a 100 amp breaker in the main. I understand that that would make the main a sub panel and I would have to separate grounds and neutrals. Just checking because 100 amp transfer switches are hard to get from Generac
 

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
from meter socket
Actually from service point. Usually point from POCO wire transtions to the wire that is controlled by NEC requirements. The requirements are that of any service conductors sizing, either size wire for breaker or breaker for the wire size.

Then feeders from your ATS to the house panel (now becoming a sub panel, seperate N/G) need additional protection at its size rating. If you are on 2017, if on 2020 code, there is exceptions or allowances to not have to alter the original panel to seperated N/G. But generac doesn't mfg an ATS to comply with this exception.
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
Irrespective of what may or may not be a Code issue let's think logically. If you have an existing 100A meter pan, the lugs are sized for 100A service conductors (let's assume for the moment that it's 2-2-4 AL SE cable). The lugs in the meter pan probably won't fit 4/0 AL which is what you'll need for a 200A transfer switch. That means on the load side of the 200A transfer switch you cannot feed the MBP with #2 AL. That's my thinking. Someone correct me if I'm wrong.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
If the 200 amp ATS is the service disconnect then you need 200 amp conductors feeding it.
 

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
If the 200 amp ATS is the service disconnect then you need 200 amp conductors feeding it.
True but if the ATS is one that is not with overcurrent protection style it is only bus rating and protection of conductors remain at the first overcurrent protection device and can be less than the ATS bus rating just not more. Generac doesn't offer one that meets that requirement as yet.

Irrespective of what may or may not be a Code issue let's think logically. If you have an existing 100A meter pan, the lugs are sized for 100A service conductors (let's assume for the moment that it's 2-2-4 AL SE cable). The lugs in the meter pan probably won't fit 4/0 AL which is what you'll need for a 200A transfer switch. That means on the load side of the 200A transfer switch you cannot feed the MBP with #2 AL. That's my thinking. Someone correct me if I'm wrong.
True but work around with a crimp reducer could be added to the 4/0. But you could still use the smaller conductor as feeder conductors (no longer service conductor after the first overcurrent device) so long as you have the correct size breaker on the load end of the feeder if you can meet requirements for tap conductors.
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
Maybe you can buy the 200A xfer switch and then get a 100A replacement main breaker. Of course you're gong to pay a premium for all that but welcome to America. :cool:

I'm guessing you'll probably void the listing on the xfer switch but that's another story. I don't see that as being any worst than some of the suggestions so far.
 
Top