Tap for Fire Pumps

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mike w

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An electrical contractor, as an afterthought, wants to tap (hard wire) the 1200 amp factory switchboard after the utility metering section, but before the 1200 amp main disconnect for fire pumps. He desires to make this tap with a 200 amp (3/0 copper conductor) circuit. (200 + 1200 = 1400 amp?). Internally in our company we state the customer must meet or exceed his main disconnect. For multiple main situations contained in a single bussed enclosure, the customer must meet or exceed the main buss rating only, not the sum total of the disconnects acceptable by the 6 switch rule.

What am I missing or not reading correctly in the NEC? Would fire pumps be an exception because of intent to run until the pump is purposely shut down, or the pump itself is destroyed?
 
The only code I have handy right now is the 1999 NEC. Article 695-3(1) allows a fire pump tap ahead of the main. 230-82(4) describes this tap as one that is supplied with the service equipment, which yours is not. I read this to mean that the lugs for this tap would have needed to be factory installed to allow for proper space and protection of these connections. As far as the 1200 amp UGP, your main is most likely rated at 80% which is 960 continuous amps plus the 200 for the fire pump for 1160 amps. I doubt you would be drawing 1200amps at the same time the fire pump was running, but thats just an opinion.
 
I'll take a crack at this one since I like discussing fire pumps.

First, what is the size of the fire pump (HP) ?

Where does the contractor propose to make the tap ? Per 695.3(A)(1), the tap can not be made in the same vertical switchboard section as the main disconnecting means.

I'm not sure what you mean by the statement that the contractor must "meet or exceed his main disconnect". Article 695 of the Code gives specific direction as to the size of conductors for the fire pump feeder. Also, 695 and NFPA 20 are very specific on the installation and routing of the fire pump feeder.

I'd advise your contractor to thoroughly read and make sure he understands Article 695 and it wouldn't hurt to get a copy of NFPA 20 also. It's downloadable from NFPA.
 
Article 695.3A1 clearly states " A connection ahead of and not within the the same cabinet enclosure or vertical switchboard section"
The disconnectiong means must also be UL listed as a Fire Pump The disconnect must sized at 4 times the locked rotor current of the fire pump.
The supply conductors and control conductors must also meet the requirements of 695.
 
"The disconnectiong means must also be UL listed as a Fire Pump The disconnect must sized at 4 times the locked rotor current of the fire pump"


I see in 695.4(B)(2)(1)
That is has to be suitable as service equipment.
Where does it say it has to be listed as a Fire Pump disconnect?
 
The disconnect must sized at 4 times the locked rotor current of the fire pump.
Click to expand...
Joe
I think you ment to say 4 time the FLA of the pump. However, the code says "lock rotor amps". 4 times the FLA may not be the lock rotor amps.
The motors listed in 430.250 have lock rotor amps listed in 430.251(B)
that are in the range of 6 times the FLA.
 
I can not figure out how to post a reply to a specfic question, so i will reply in general

695-4-1 Overcurrent device selection. This requires the overcurrent device to carry ' indefintally" the locked rotor current of the fire pump.
The locked rotor current is listed on the name plate of the motor. If it is unknown it is 4 times the FLA of the motor.

The disconnect must be sized to carry this load as well
 
Joe Gauthier said:
I can not figure out how to post a reply to a specfic question, so i will reply in general
Click to expand...

Simply use the
icon_quote.gif

button from the particular post to which you want to respond, and edit it down to the specific question you want to answer. :)
 
Joe,
The locked rotor current is listed on the name plate of the motor. If it is unknown it is 4 times the FLA of the motor.
Click to expand...
Where does the 4 times come from? That would be too low for many motors.
Don
 
From the Handbook, 695.4:

Step 1.
Determine the minimum ratings of the disconnecting means and the overcurrent protective device. According to the motor nameplates, the locked-rotor current (LRC) is 725 amperes for the 100-hp motor and 20 amperes for the 11/2-hp motor. If the locked-rotor amperes are not on the nameplates, the locked-rotor currents found in Table 430.151(B) must be used.
 
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