Fire Pump Feeder

lkdiaZ

Member
We are working on the redesign of the electrical system for a building which will include a new fire pump.

The redesign will require that we install a new medium voltage pole riser which will in turn feed a non utility owned medium voltage transformer. Because this transformer is owned by the building it is my understanding that the service is from the point of connection to the utility at the pole riser and down to the medium voltage transformer. It is assumed that the medium voltage service disconnect will be incorporated into the medium voltage transformer or upstream of it. The secondary of the transformer which will be at the operating voltage of the building loads and the fire pump as well is therefore technically a feeder and not a service. We would like to provide 2 feeders from this transformer, one for the building load and one for the fire pump. This would be comparable to running 2 separate services should the transformer be owned by the utility. Is this code compliant?

Here's our confusion:
695.3(A)(1) - deals with separate service connection or taps ahead of the main service disconnect. In our case the service occurs at the medium voltage level. This would imply that we have to branch off the medium voltage service in two different directions. One to feed a medium voltage transformer for the building loads and one to feed a second medium voltage transformer for the fire pump.
695.3(A)(3) - what we are hoping is that this section which allows for a dedicated feeder to a fire pump allows us the relief to install one medium voltage transformer that supplies two separate feeders as stated in the introductory paragraph. One for the building load and one for the fire pump. We are getting hung up on the wording "where it is derived from a service connection as described in 695.3(A)(1)" and therefore are not sure if our intended design meets this criteria.

It seems somewhat excessive that if this transformer was utility owned and the secondary was therefore a service that we could run both services from this same transformer but the fact that it is a non utility owned transformer requires us to install two transformers. I'm not sure that the electrons care or behave differently knowing that one entity or the other owns them.

I should add that this is a single building and not a campus style setting.

Hoping someone can shed some feedback.
 
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