Using a residential transformer for industrial loads.

[BenS]

I am trying to come up with a reasonable solution for providing power to a 3hp pump. The pump is physically located adjacent to a company provided housing unit, which has a 480-240/120 27KVa transformer. No other power is near the pump's location. Previously, it appears people were tapping in directly to the transformer secondaries with 10/3 cord without even so much as a disconnect or breaker anywhere in the circuit. Not good.
The transformer feeds the service mains for the two sections of the housing unit. I thought about adding a circuit to one of the load center's, but they were both completely full. My next thought was to add another service disconnect for the pump, which would be located adjacent to the meters for the two units on the exterior of the building. I realize most people would never be able to consider this option, but considering there is no utility company involved, the transformer is one of four served by a 125 amp breaker, and the transformer itself is relativity small I am thinking I might be able to make it work. Only other option I see is getting a entirely new service entrance with service for three mains instead of two.

 

[augie47]

In this area, you could not add the disconnect adjacent to the meters on the building unless there were disconnects outside already ( (230.72). Since the pump is remote from the building, you could go from the transformer to a disconnect at the pump. (similar to the cord, but properly with a disconnect)
curious, no utility involved but there are meters ?? will the pump not be metered ?

 

[iwire]

The transformer feeds the service mains for the two sections of the housing unit.................

I realize most people would never be able to consider this option, but considering there is no utility company involved, the transformer is one of four served by a 125 amp breaker,

First off if there is no utility involved then there is no 'service' to these buildings. Only the utility can provide a service (See Article 100 definition of 'service'. Why is this important? Because it changes the rules we must follow, services are covered by Article 230, what you have are feeders. And part II of article 225 applies to them.

Now that said you are allowed to tap the transformer multiple times right at the transformer, you can not tap the existing conductors.

Also the total of the over current protection must not exceed what would be allowed for a single over current device. See Table 450.3(B) Note 2.