Adding a generator to power building, requirements for existing fire pump

[gernsperger]

Our company is adding a generator to power our manufacturing facilities in the event of an extended power outage, we have a fire pump, what are the requirements for the existing fire pump. Location is Michigan[pre][/pre]

 

[jraef]

There are a lot of specific requirements for fire pumps and back-up generators that must power them, both from an engineering standpoint and a code compliance standpoint. I believe this is too critical and important to be considered a "tip" from an anonymous website, if you are not already familiar with this issue, as it appears you are not. I highly suggest hiring a local qualified consultant for this. There are PEs who specialize in Fire Pump system engineering.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[dpc]

If you have an existing fire pump, presumably it already meets the NEC power supply requirements for powering from a utility source. If the generator being added is NOT a legally-required emergency or standby generator, I don't think you would have to change anything related to the fire pump - at least in terms of the NEC. If you desire to power the fire pump from the generator, then you would need to make sure the engine-generator is large enough to start the fire pump and you may want to get some professional help as Jeff suggested.

 

[jmbelectrical]

As jraef and dpc pointed out, the NEC contains numerous requirements pertaining to fire pumps and generators. The following are just a few that come to mind:

1. 695.14(F) outlines mechanical/fire protection requirements for the control wiring from the generator to the fire pump controller.
2. 695.7(B) requires that the voltage at the fire pump motor's terminals not exceed 5 percent when operating at 115 percent of full load current.
3. 695.7(A) requires that the voltage at the fire pump controller's terminals not exceed 15 percent upon startup, however, generators are exempt from this requirement. (Regardless, the generator should be sized to ensure that the voltage drop won't be high to the point at which the fire pump controller is unable to start the fire pump.)
4. 695.4(B)(2) outlines circuit breaker sizing requirements for a generator serving a fire pump.

 

[davidbeach]

2. and 3. above - "the voltage at the" should read "the voltage drop at the".

 

[jmbelectrical]

davidbeach,

Thank you for catching that! I guess this is what happens when I drink and post on Eng-Tips at the same time.

 

[waross]

When sizing the gen-set the largest motor to be started on the gen-set should be sized at 300%.
While this is a rule of thumb, it may be well to re-appraise any installation which doesn't meet this rule.
If the largest motor is not a significant portion of the load on a prime rated gen-set this rule may be relaxed somewhat.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

I think bill was drinking too. He means the generator should be 300% the size not the motor.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[dpc]

Eng-Tips can seem so serious when you're sober!

 

[waross]

I meant 3 times the size of the motor.
To start a 100 Amp FLC motor, the generator should have 300 Amps available capacity.
Use current or KVA, not kiloWatts. Motor starting current is at a low power factor so the generator KVA rating is the limit, not the kW rating.
I agree with you Keith. Very poor wording.

Bill
--------------------
"Why not the best?"
Jimmy Carter