lkdiaZ
Member
- Location
- Virgin Islands
- Occupation
- Electrical Contractor
I posted this question in Engineering/Calculations without any luck on feedback a few days ago. Hoping someone here can provide some insights.
I'm rewording it a little different.
In new construction, for a building that includes a fire pump and the medium voltage transformer that steps down to the building and fire pump voltage is owned by the utility, we would run one service to the building loads and a separate service from the same transformer to the fire pump.
We have a condition where the same medium voltage transformer as in the example above is customer owned. Technically the primary side of the transformer now is the incoming service and the secondary is a feeder. 695.3(A)(1) requires that a separate service or a tap ahead of the service disconnect is required for the fire pump. 695.3(A)(3) does allow a feeder that is derived from 695.3(A)(1). I'm not sure I fully understand 695.3(A)(3). It says that a feeder is allowed. The secondary of our transformer is a feeder so we are good there so far. But does the fact that it needs to be derived from a service as specified in 695.3(A)(1) indicate that we have to tap the incoming service which is at medium voltage and run to a second medium voltage transformer dedicated specifically to the fire pump? In which case the mere fact of who owns the transformer causes us to have to install a second transformer to be in compliance.
Logic dictates that if one transformer is a safe installation if it's utility owned why would it be less safe if the exact same transformer is customer owned.
Curious to hear how others interpret this.
I'm rewording it a little different.
In new construction, for a building that includes a fire pump and the medium voltage transformer that steps down to the building and fire pump voltage is owned by the utility, we would run one service to the building loads and a separate service from the same transformer to the fire pump.
We have a condition where the same medium voltage transformer as in the example above is customer owned. Technically the primary side of the transformer now is the incoming service and the secondary is a feeder. 695.3(A)(1) requires that a separate service or a tap ahead of the service disconnect is required for the fire pump. 695.3(A)(3) does allow a feeder that is derived from 695.3(A)(1). I'm not sure I fully understand 695.3(A)(3). It says that a feeder is allowed. The secondary of our transformer is a feeder so we are good there so far. But does the fact that it needs to be derived from a service as specified in 695.3(A)(1) indicate that we have to tap the incoming service which is at medium voltage and run to a second medium voltage transformer dedicated specifically to the fire pump? In which case the mere fact of who owns the transformer causes us to have to install a second transformer to be in compliance.
Logic dictates that if one transformer is a safe installation if it's utility owned why would it be less safe if the exact same transformer is customer owned.
Curious to hear how others interpret this.
