Fire Pump Short-Circuit/OCPD

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Canton

Senior Member
Location
Virginia
Occupation
Electrician
A full service listed fire pump controller with a SUSE rating can be directly connected to service conductors. It is the service disconnecting and OC protection. As long as the service conductors are outside the building (using the NEC definition of outside) it is compliant. See 695.4(A). While the UL standard does not require FP controllers to be SUSE rated, as a practical matter, I've never seen one that wasn't. As I mentioned previously, for most installations this is the simplest and least costly way to go.
In cases where you can't get service conductors directly to the FP controller without going through the building then you can use 695.4(B) and install the supply as a feeder. The big down side to this method is that the disconnect will have to be rated for locked rotor and the feeder installation will have to have a 2 hour fire rating. This can get quite costly.

Thank you for the information!
 

david luchini

Moderator
Staff member
Location
Connecticut
Occupation
Engineer
It is locked rotor current of the main motor + the full current load of the maintenance pump motor and the full load current of the fire pump accessories NEC 695.4 B(2)(A)

I think it would be the locked rotor current of the main motor + the locked rotor current of the maintenance pump motor and the full load current of the fire pump accessories per NEC 695.4(B)(2)(a).
 

iwire

Moderator
Staff member
Location
Massachusetts
So I happened to visit a friend working in a fire pump room. The sprinkler contractors had the fire pump down for testing so I took the opportunity to snap some pictures for those that do not get to see fire pump controllers.

This one has both a utility feed and a generator feed.
 

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Canton

Senior Member
Location
Virginia
Occupation
Electrician
So I happened to visit a friend working in a fire pump room. The sprinkler contractors had the fire pump down for testing so I took the opportunity to snap some pictures for those that do not get to see fire pump controllers.

This one has both a utility feed and a generator feed.

That is very similar to what I'm used to seeing with OCPD for normal and emergency. The one at my job looks the same but inside it looks like a standard ATS with no OCPD's....I will be there Tuesday and take some pictures to compare. Thanks for sharing.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
So I happened to visit a friend working in a fire pump room. The sprinkler contractors had the fire pump down for testing so I took the opportunity to snap some pictures for those that do not get to see fire pump controllers.

This one has both a utility feed and a generator feed.
Do we get to nit pick? At first glance I see a few violations.:)
 

Canton

Senior Member
Location
Virginia
Occupation
Electrician
No problem at all. It just worked out funny, I got done a bit early on Friday and found myself standing in front of a shutdown fire pump controller. Figured I could snap a few photos and post them.

Interesting turn of events today. I went to go take some pictures of the Fire Pump Controller today at the job.....and its gone. I asked the Sprinkler contractor what happened to it. Turns out that controller was for another job and their shop sent out the wrong one...:? The correct one is being sent out next week.

I asked some questions trying to get some info on make and model but the Sprinkler Fitter looked at me like i was speaking another language. I wonder if this one will come with OCPD's built in like the one posted...? I'll post some pictures when I see it.
 

wireddd

Member
No confusion here. The object is to have the fire pump run in a emergency until it literally melts itself into the ground. Did one recently, had to tap the main buss on a 3000 amp 480 volt service buss on the electric co side with #2 conductors feeding a 400 amp CT cabinet with a 45 amp load with 350 amp time delay fuses in the controller.

Keep in mind that many people do not exit a building when the fire alarm goes off. The fire pump must run until they decide that they have finished the file they were working on and indeed there is a fire. Then they exit.
Also many people do not maintain fire pumps like they should and many have a locked shaft at the pump due to no maintenance. the motor must break this loose and could cause a main overcurrent device to trip.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
No OCPD, connected directly to the service transformer - yep.

I was involve in repairing a fire pump feeder - mid 1990s. Parallel 250kcil, maybe 750 feet, 3" rsc, 3' burial, concrete incased. Fault developed in the middle of one of the 3" rsc.

Service was 480 grnd Y, 750kva, utility owned oil filled pad mount, ug 34kv primary fed from pole outside the plant, xfm located inside the plant ~75" from the outdoor serviceequipment.

Showed up in the morning to bad electrical - looked like one or two phases out.

Called the power company, they came out and replaced the transformer 34kV primary bayonet fuses. They don't have the 10A fuses so they use 30A. Lineman turns switch on the xfm. Transformer starts rumble, smoke starts coming out of the service equipment. Lineman drops the pole he is holding for the xfm switch actuation. Runs over to truck, parked out by the pole, jumps in the bucket, goes up and jerks the cutouts open.

It was obvious which conduit had the fault. The locknuts were burned off, melted. The wire insulation from that conduit was bubbled, scorched.

Connected a boom truck to the conductors at the fire pump end and pulled until we tore them off. Pull the other end till we tore it off. Laid the conductors on the ground over the conduit path. We dug up the conduits where the 6' section was missing. Yep - burned and melted right clear though the conduit. Concrete and 2" minus backfill looked like it was trying to turn into glass.

I have no clue as to how/why the cable decided to fault after 5 years in service, in the middle of the run, in conduit, concrete incased. No backhoes, no water, didn't see any rocks in the conduit when I pulled out the wires. No obvious nicks in the insulation - at least none that I could tell were there before we pull them out with a boom truck. :?

So I am asking the fire marshal, How about we install a mag only CB for the fire pump feeder? I offered a 1200A frame, 4000A instantaneous only. In 30 years there had never been a fire that threatened the plant. The fire pump feeder failure could have taken out the whole place. I don't know where the electrical would have burned clear had the lineman not pulled the pole cutouts - I suspect when the xfm blew up

Fire Marshal said No. No OCP between the service and the fire pump controller. He absolutely understood the NEC allowed appropriatle sized OCP.

I'm still baffled as to the cause. But I think the Fire Marshal considered the failure a way-the-hell-out-there-fluke.

I'm not saying the fire marshal is wrong ..... but ....... Nah, no buts. I'm not saying he was wrong

ice
 
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