Fire Pump Service & Utility Company Responsibilities?

[gadfly56]

I'm paraphrasing here, but the first sentence basically says "Where the service voltage is different than the fire pump voltage a transformer shall be permitted between the system supply and the fire pump controller."

So this only applies when the source voltage is different than the fire pump voltage. Note that "source" or "service" refers back to the sources listed in 695.3, so the source or service is the "Electric Utility Service Connection". As a result, 695.5 only applies for a customer owned transformer after the service, or a transformer connected to a generator or an on site power production facility.


Again, I still agree with you that the utility primary fusing should carry the locked rotor current, or an alternate source must be provided, but that's just not the right paragraph to quote.

I do not agree with this:



And overcurrent protection is permitted on the secondary side of a utility transformer that supplies a fire pump, just not on the secondary of a privately owned transformer.

There is no customer owned transformer. There is ONLY the POCO transformer. Now what????

 

[steve66]

There is no customer owned transformer. There is ONLY the POCO transformer. Now what????

Then they can have a disconnect with overcurrent protection between the service and the fire pump per 695 B 1. The OCP does have to be able to carry the locked rotor current indefinitely.

And from your first post, I believe the utility needs to size the primary OCP to also carry the locked rotor current indefinitely, or an alternate source needs to be provided (for example, an emergency generator).

 

[Skokian]

Measure the Starting and Running Voltage Drops.

Measure the Starting and Running Voltage Drops.

It does occur on occasion that a dedicated utility transformer is undersized. NFPA-20 requires that the voltage drop at 1.15% of FLA be no more than 5% at the motor terminals. Also note that it's now legal to measure the motor voltage at the fire pump controller's motor conductor terminals rather than at the motor junction box.

The voltage drop during starting must not exceed 15% at the controller's inlet terminals. Also note that the motor starting current is LRA for A-T-L (D-O-L) controllers; but, will be a lessor number for any form of reduced voltage (reduced inrush) starting type controllers. These include:

1) Part Winding,
2) Primary Resistor,
3) Primary Reactor (or neutral reactor in medium voltage controllers above 5.0 Kvac),
4) Wye-Delta (Open or Closed Transition types),
5) Autotransformer, or
6) Soft Start.

Also note that variable speed controllers in the full speed (non-VFD) mode can be types 1), 2), 3) or 6) above.

For transfer switch type fire pump controllers supplied by a local gen set, 2) is the worst starting type since the Kw demand is even higher than A-T-L starting. 5) is the best followed by 3) or 6). 1) is also OK; but, isn't often used at present. Also 4) is problematic since most manufacturers impose a transition delay which causes A-T-L current to finish accelerating the motor.

Hope this helps some.