Generator Disconnect

[wirestu]

We have a job which has an outdoor walk in enclosure outside a building for an emergency generator set. The switchgear and ATS are inside the building. It is more than 50 feet and out of sight. The questions is: Is a emergency disconnect required for the generator feeder inside the building before the ATS

Thanks,

Stu

 

[don_resqcapt19]

Re: Generator Disconnect

Stu,
In my opinion, 225.31 requires that the generator feeder circuit have a disconenct at the main building.
don

 

[arneykaner]

Re: Generator Disconnect

Yes, a disconnect is required per 225.31.
However, if you have a fire pump fed from that generator, the fire pump should be fed from the generator's circuit breaker directly, no additional disconnect is allowed.

 

[bennie]

Re: Generator Disconnect

A switch for isolation purposes is permitted ahead of the transfer switch.

The transfer switch should meet the requirements of 225.31.

This disconnect should not be an overcurrent device.

Adding the switch compromises the continuity of service for the generator.

 

[hornetd]

Re: Generator Disconnect

OK, I need to resort to examples in order to understand when a disconect is required between a transfer switch and an engine alternator set (generator).

If the set is located out of sight from, but inside the same building as, the transfer switch is any disconnect required? No.

If set is located in a separate building is a building disconnecting means required. Yes.

If the set is located outdoors in weatherproof housing immediately adjacent to the building served, five feet of flex to conduit change over fitting to LB into building is a Building disconnecting means required? Yes/No.

Set located away from building outdoors in weatherproof housing but not in another building. Building disconnecting means required? Yes/No?

Let's keep in mind that the section under discussion here is 225.31 that is found in the sub chapter entitled "II. More Than One Building or Other Structure."
--
Tom

 

[bennie]

Re: Generator Disconnect

A generator in one building, supplying power to another, has to be regarded as if it is a transformer supplied by the utility.

The object of most generators, is to supply power in adverse conditions.

The only switches, or overcurrent devices, should be the ones necessary to provide continuity of operation.

The transfer switch, is the only equipment required in the feeder, from the generator, to the premises wiring.

No other disconnects, or overcurrent devices, should be in the circuit.

Most generators are inherently protected from overloads.

[ April 27, 2003, 04:52 PM: Message edited by: bennie ]

 

[don_resqcapt19]

Re: Generator Disconnect

The code requires a disconnect at the building in all cases where the generator is not in the same building. A transfer switch that can be manually operated could serve as the required disconnect if located as required by 225.32.
Don