Overcurrent Protection, Fire Pump

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ethwinfir

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I would appreciate some input on the required overcurrent protection for a fire pump motor installation as I describe below.
A fire pump controller, which has a transfer switch , is being supplied from a utility transformer with an unfused disconnect being inserted between the transformer and controller. The conductors from the unfused disconnect are terminated to a 150 amp circuit breaker on one side of the transfer assembly. The other side of the transfer assembly, which is another 150 amp breaker, has conductors connected to it which originate at an on site generator. My question is this; Does the overcurrent protection for the fire pump motor have to be capable of carrying the locked rotor current of the motor for an indefinite period of time? Article 695 of the NEC is somewhat unclear to me. I'm trying to apply 695.4 (A) of the 2005 NEC to make this call.
Thanks in advance for any comments.
 
Re: Overcurrent Protection, Fire Pump

I am lookiing at my 1999 NEC and I don't think there has been any change in the locked-rotor requirement. The overcurrent protective device(s) shall be selected to carry indefinitely the sum of the locked-rotor current of the fire pump motor(s) and the pressure maintenance pump motor(s) and the full-load current of the associated fire pump accessory equipment. I think the intent is if the building is on fire, what would be the purpose of saving the fire pump at the risk of the loss of life and property.
 
Re: Overcurrent Protection, Fire Pump

Bob and Grant, Thanks for your input on this. I, in error, stated that there was a disconnect switch between the utility transformer and the fire pump circuit breaker. There is no disconnect switch at this location, which would make it a direct connection. This leads me to the question, since it is a direct connection, 695.4 (A), would the wording under 695.4 (B) apply? I really appreciate you guys taking the time to give me your opinions on this.
 
Re: Overcurrent Protection, Fire Pump

In my opion 695-4 Continuity of Power speaks of Circuits (meaning more than one) shall be supervised ( I assume your installation is) from inadvertent disconnection as covered in (a) OR (b). I take this to mean the service from the utility is a Direct Connection in your case and covered under 695-4(a) while the remote generator supply is covered under 695-4(b) where a disconnecting means that is supervised would be allowed. Both the 150/3 breakers are required to carry the locked-rotor current.
 
Re: Overcurrent Protection, Fire Pump

The controller must be rated as service equipment also and will carry locked rotor current for about 20 seconds before opening up. They just want to make sure that any circuit feeding it will carry locked rotor for an indefinite period of time. :D
 
Re: Overcurrent Protection, Fire Pump

The controller must be rated as service equipment also and will carry locked rotor current for about 20 seconds before opening up.
Click to expand...
Charlie
When you say "controller" are you speaking of the fire pump equipment?
 
Re: Overcurrent Protection, Fire Pump

Yes, it must be a listed fire pump controller. Anything else in front of it will be required to carry locked rotor current. Excessive voltage drop at locked rotor will not be permitted either.

The intent is to permit the listed fire pump controlled to perform in accordance with its listing without anything else opening the circuit first. :D
 
Re: Overcurrent Protection, Fire Pump

Charlie,

When I mention controller, I'm talking about the whole transfer switch assembly which would include circuit breakers, magnetic starters, etc. This is how the package unit is referred to in the specifications.

Thanks,
Bob
 
Re: Overcurrent Protection, Fire Pump

Bob, I am talking about a listed fire pump controller, not a transfer switch (a controller like the NEC is referring to in 695.4). :D
 
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