Fire Pump Controller

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ken44

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Austin, TX
I have a hot issue that I need some help with, we had an ATS Controller for a fire pump that pulls 73 amps at 480 volts, it was delivered to the job site yesterday and the replacement ATS has 150 amp OCPD's while the existing ATS has 225 amp OCPD's. The company that designed the replacement insists that it is correctly sized in accordance with NFPA-20, while I maintain that it should have been sized at 300% of the FLA according to Article 695 of the NEC.
 
Assuming that it is a standard thermal magnetic breaker and not an instantaneous trip device, I would agree that the 150 amp breaker is unlikely to have a trip curve that meets the requirements of 695.4(B)(2).
 
I have a hot issue that I need some help with, we had an ATS Controller for a fire pump that pulls 73 amps at 480 volts, it was delivered to the job site yesterday and the replacement ATS has 150 amp OCPD's while the existing ATS has 225 amp OCPD's. The company that designed the replacement insists that it is correctly sized in accordance with NFPA-20, while I maintain that it should have been sized at 300% of the FLA according to Article 695 of the NEC.

You need a sit down with the manufacturer providing the controller. Unless they've been mislead as to the size of pump this combo controller will feed, they usually know what they are doing re OCPD's.
 
Assuming that it is a standard thermal magnetic breaker and not an instantaneous trip device, I would agree that the 150 amp breaker is unlikely to have a trip curve that meets the requirements of 695.4(B)(2).

I wouldn't make that assumption. We've had presentations by pump manufacturers and IIRC this issue crops up regularly. One of them has a handout they fax to AHJ's all the time.
 
I wouldn't make that assumption. We've had presentations by pump manufacturers and IIRC this issue crops up regularly. One of them has a handout they fax to AHJ's all the time.
So are they using an instantaneous type breaker?
 
Fire Pump locked rotor current tolerance

Fire Pump locked rotor current tolerance

Below is a TCC that shows a 60 hp fire pump and a Cutler-Hammer J250AF/150 amp-trip breaker with 5-10X adjustable instantaneous, adjusted to 10X.
Using a locked-rotor current of 5.88 times the 60hp running amps it looks like it meets 695.4(B)2 criteria. The additional jockey pump locked-rotor current would also fit within the breaker's tolerance.
So it really comes down to the breaker being used, but chances are good that it works.
 

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  • 60HP FP.JPG
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The C-H breaker I plotted is a thermal-mag breaker as well. What's the part number?

Part # SQD HGL36000S15. There is also a tag that states:
Circuit breaker is sized per NFPA 20 F
Frame sized at 115% of FLA - 10.4.3.3.1 (1)
Trip in 8-20s at 600% of FLA - 10.4.4.(1)(a)
Hold for 3 min. at 300% of FLA - 10.4.4.(1)(b)
 
Part # SQD HGL36000S15. There is also a tag that states:
Circuit breaker is sized per NFPA 20 F
Frame sized at 115% of FLA - 10.4.3.3.1 (1)
Trip in 8-20s at 600% of FLA - 10.4.4.(1)(a)
Hold for 3 min. at 300% of FLA - 10.4.4.(1)(b)

Below is a TCC with your Square D HG breaker and the 60 hp fire pump.
The 300% level is tolerated and agrees with "holds for 3 min at 300%".
The 600% level does not "trip within 8-20 seconds", but I wouldn't want it to. Especially since it also needs to tolerate the lra of the jockey.
Bottom line is that breaker will work.
 

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Below is a TCC with your Square D HG breaker and the 60 hp fire pump.
The 300% level is tolerated and agrees with "holds for 3 min at 300%".
The 600% level does not "trip within 8-20 seconds", but I wouldn't want it to. Especially since it also needs to tolerate the lra of the jockey.
Bottom line is that breaker will work.

Many thanks for all of your help guys.
 
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