Manual Transfer Switch

[Fitzdrew516]

Recently I had designed a 3000A service to a facility. I included GFP on the main gear per code, but recently there have been some changes in the field that I want to clarify. The contractor and the client have put forth a plan to install a manual transfer switch outside the building right before the conductors enter the main gear. Questions below -

1) Does the transfer switch need to have GFP? I assume it will have to incorporate this now if there is a disconnect on the transfer switch considering that would technically be the service disconnect now.

2) The contractor had selected a 3 pole transfer switch. I know there is some give and take as to which is better: 3 or 4 pole. Does anyone have any input as to why we should go with one that disconnects the neutral as well?

Thanks,
- Drew

 

[ron]

If the MTS is upstream of what you had acting as the main, will the MTS be the new service rated disconnect?

 

[Fitzdrew516]

If the MTS is upstream of what you had acting as the main, will the MTS be the new service rated disconnect?

I'm not sure whether or not the MTS will have a disconnect on it, but every one I've ever seen has had a disconnect on it so I assumed that this one would and would now be acting as the main for the service due to it being upstream.

 

[Fitzdrew516]

I just received this breakdown. Looks like they are including GFP so that alleviates my first concern. Looks like they are opting for a 3 pole transfer switch though. Any qualms with this?

 

[Jraef]

At 3000A, that "manual transfer switch" is two interlocked circuit breakers, in this case, C-H Insulated Case Power Breakers. It's only called "manual" because they leave out the components that monitor the line and generator to transfer automatically, you have to send it commands via another control system, or walk up to it and push the buttons.

 

[Fitzdrew516]

At 3000A, that "manual transfer switch" is two interlocked circuit breakers, in this case, C-H Insulated Case Power Breakers. It's only called "manual" because they leave out the components that monitor the line and generator to transfer automatically, you have to send it commands via another control system, or walk up to it and push the buttons.

Correct, but with it being upstream of the old service disconnect, then this would now be the new service disconnect, correct?

 

[dkidd]

Correct, but with it being upstream of the old service disconnect, then this would now be the new service disconnect, correct?

Yes. Things to consider include removing the existing neutral to ground bond, and

230.91 Location. The service overcurrent device shall be
an integral part of the service disconnecting means or shall
be located immediately adjacent thereto.

 

[ron]

Since it is 3 pole transfer, the "other" source will need to be NOT separately derived, which means no N-G bond on the "other" source.

 

[Jraef]

I believe though that you have to order it AS the Service Entrance rated version in order to get the SUSE label.

 

[bsmith8691]

It does have to be listed and rated as service entrance equipment. Unless I've missed something, on a stationary standby you don't need the fourth pole to be disconnected.

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