300amp service transfer switch instillation question

[delfadelfa]

I call my rep at generac and he said what I want to do can't be done so here's my story. I bidding a generator for a 10 year old house with a 300 amp service and propane heat. The owners want to be able to transfer the whole house to generator. The 300 amp double lug meter base is outside. Two 150 amp feeds come out of the meter base and go into the basement to two 150 amp disconnects. Each disconnect feeds a 30 circuit panel located in two different areas of the house about 75 feet away from the disconnects. I need help engineering the transfer switch or switches. I have room to install them by the two disconnects. This is a very common set up for a 300 amp service, so I'm thinking somebody out there has run into this before. Thanks

 

[mcclary's electrical]

I call my rep at generac and he said what I want to do can't be done so here's my story. I bidding a generator for a 10 year old house with a 300 amp service and propane heat. The owners want to be able to transfer the whole house to generator. The 300 amp double lug meter base is outside. Two 150 amp feeds come out of the meter base and go into the basement to two 150 amp disconnects. Each disconnect feeds a 30 circuit panel located in two different areas of the house about 75 feet away from the disconnects. I need help engineering the transfer switch or switches. I have room to install them by the two disconnects. This is a very common set up for a 300 amp service, so I'm thinking somebody out there has run into this before. Thanks

How hard would it be to change SE conductors that go to disconnects?

 

[delfadelfa]

Not hard. They are only about 8 feet long. Right out of the bottom of the meter base - through the foundation - and right into the surface mounted disconnects in the basement. I was hopeing to save the disconnects so I did not have to buy a 300amp service main breaker transfer switch because I did not know how to feed the two sub panels from the 300amp transfer switch.

 

[mcclary's electrical]

Not hard. They are only about 8 feet long. Right out of the bottom of the meter base - through the foundation - and right into the surface mounted disconnects in the basement. I was hopeing to save the disconnects so I did not have to buy a 300amp service main breaker transfer switch because I did not know how to feed the two sub panels from the 300amp transfer switch.

Well my recommendation was going to be exactly what you are trying to avoid. :roll: But that's how I would do it

 

[delfadelfa]

How do I fuse the two 150 amp subpanels from the 300amp ATS? I have installed a few 200amp one but I have not seen a 300amp. Do they make them with two 150amp main breakers?

 

[LarryFine]

I think the closest you'd get would be to use a 400a service-rated T/S, and then split the output of that.

If it were me, I'd try hard to have one panel transfer to the generator, and have one panel not transfer.

You're going to have trouble transferring the entire house automatically unless it's a very large generator.

 

[kbsparky]

Use a 4-pole transfer switch, and you can keep all your disconnects intact.

 

[delfadelfa]

I think the closest you'd get would be to use a 400a service-rated T/S, and then split the output of that.

So put the 400a service-rated T/S after the meter base and before the two existing 150a disconnects. Relocate the driven and water grounds to the service-rated T/S now that it is the main service disconnect.

 

[LarryFine]

Yepperoni.

 

[don_resqcapt19]

So put the 400a service-rated T/S after the meter base and before the two existing 150a disconnects. Relocate the driven and water grounds to the service-rated T/S now that it is the main service disconnect.

The service OCPD is required to be within or adjacent to the service disconnect. Does the service rated transfer switch have OCPD built in?

 

[delfadelfa]

The service OCPD is required to be within or adjacent to the service disconnect. Does the service rated transfer switch have OCPD built in?

I'm thinking that's what makes it service rated. One 400a breaker.

 

[Cow]

I'm thinking that's what makes it service rated. One 400a breaker.

Don't make an assumption. For example, Cutler Hammer makes a service rated transfer switch with no OCPD in it.

 

[delfadelfa]

Don't make an assumption. For example, Cutler Hammer makes a service rated transfer switch with no OCPD in it.

At 400 amps what would it be protecting anyway. Would not the real protection be the two 150 amp disconnects six inchs below the 400 amp ATS?
And if it does or does not provide OCP can I use it as a main for the service? I mean even if it was a OCPD can you put a 400 amp main on a 300 amp service? Thanks