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#64043 - 03/29/06 09:39 PM Fire pump service  
Jps1006  Offline
Member
Joined: Jan 2004
Posts: 615
Northern IL
I have a 60 HP fire pump I'm still playing with. FLC 169 amps at 208V. CT cabinet (no disconnect) will be 400-amp 3-phase. I noticed the AIC rating of the CT is 10,000 amp. The utility transformer is 500KVA.

My very rough estimate is 1388-amps for a possible AFC of 13,880 (I know this is rough). When bringing this up to my supplier, he tells me the only way to get AIC of higher I have to put a disconnect in it. Well that puts me up to a 1200-amp disconnect. (fire pump rules- NEC '99 695-4 for you savy types)

This seems odd that with disconnect it would be rated at 100,000 but without only 10,000. Any input or suggestions??


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#64044 - 03/29/06 10:05 PM Re: Fire pump service  
Ron  Offline
Member
Joined: Mar 2002
Posts: 582
White Plains, NY
Is it just a disconnect or a fused disconnect? Many disconnect only switches are only rated 5-10kA withstand, whereas a fused disconnect usually will take on the AIC rating of the fuses you install.


Ron

#64045 - 04/05/06 10:13 PM Re: Fire pump service  
Jps1006  Offline
Member
Joined: Jan 2004
Posts: 615
Northern IL
Ron,

I was planning on going with no disconnect, just CT cabinet. The controller would be the service enterance equipment.


#64046 - 04/06/06 11:57 PM Re: Fire pump service  
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
I've never installed a fire pump without a disconnecting means.

Just how is the service tech going to be able to work on it now that OSHA has weighed in on hot work?

Try and get a hold of the FrenchElectrician: he's an expert on fire pumps.

All of my fire pumps were designed by a committee: the AHJ, FM, pipe fitters, pump techs, EE's all jumped in the soup. You have to make them all happy.

I've never seen any engineering short-cuts withstand the process.

They want what they want, and a contractors opinion counts as a negative.

I never try to design or tweak fire pump systems. You can't win.


Tesla

#64047 - 05/08/06 01:44 PM Re: Fire pump service  
Jps1006  Offline
Member
Joined: Jan 2004
Posts: 615
Northern IL
Thanks for the input guys.

The owner of the building has had his architect buddy call on his EE pal to review a fire pump plan. The plan is to come out of the utility transformer to a 400 amp CT cabinet (no disconnect) and then run up and over the rooftop, then down the other side of the building to the fire pump room into the service equipment rated controller with built-in disconnect.

The EE says "The code interprets conduit attached to the building roof as inside the building (as there is not sufficient fire protection)....... A method to alleviate this violation alltogether would be to provide a main disconnect adjacent to the CT cabinet."

I spoke to him by phone and asked for a reference and he said he didn't have it handy, but it was either NEC or NFPA20. I didn't press the issue because I'm under the impression he is advising as a favor. The local inspectors tell me they think he is wrong and they will approve of the service entrance conductors run over the building.

Any opinions, references or suggestions?


#64048 - 05/08/06 03:33 PM Re: Fire pump service  
mxslick  Offline
Member
Joined: Oct 2004
Posts: 803
Atomic City, ID USA
Quote
..... into the service equipment rated controller with built-in disconnect.


Tesla, I think that would satisfy the concern of the fire pump technician's working on the system.

However:

Quote
The plan is to come out of the utility transformer to a 400 amp CT cabinet (no disconnect) and then run up and over the rooftop, then down the other side of the building to the fire pump room.....


sounds like this run will be well in excess of say, 25 feet or so...

and

Quote
The EE says "The code interprets conduit attached to the building roof as inside the building (as there is not sufficient fire protection).......


A very astute and correct observation...


and

Quote
The local inspectors tell me they think he is wrong and they will approve of the service entrance conductors run over the building.


I wonder if these local inspectors would care to be the ones on the rooftop during a fire event in this building when that unprotected feeder run (with no disconnect, remember) faults from the heat buildup on the roof or if flames from within penetrate the roof and overheat the conductors within the conduit!! This is being fed from a 500kva transformer!!

A stupid plan, with very serious consequences possible. At the very least have a disconnect at the CT cabinet capable of killing that feeder under fault current conditions.

Just my 25cents. [Linked Image]


Stupid should be painful.

#64049 - 05/08/06 06:15 PM Re: Fire pump service  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Quote


quote:
--------------------------------------------------------------------------------
The EE says "The code interprets conduit attached to the building roof as inside the building (as there is not sufficient fire protection).......
--------------------------------------------------------------------------------

A very astute and correct observation


I disagree.

I sure would like to see some code reference for that.

If the conduit is on the outside f the roof than the conduit is in fact outside the building in NEC terms.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#64050 - 05/08/06 06:37 PM Re: Fire pump service  
frenchelectrican  Offline
Member
Joined: Feb 2003
Posts: 939
Wi/ Paris France { France for ...
for the firepump set up there are few thing i am little consdering about this ;,,

the conduct running top of the roof ? well did the inspector and EE and Fire inspector approve this kind of methold ??

i am very lerry with this set up because you did mention CT cabent with no disconnect means.

where is the controller will be located ?? it will play big diffrence there

but i did look for NEC code related with the conduct for running on roof for fire pump set up and i have few conflet answer there so my best bet is check with your local inspector for further details

i dont know if you have other option you can run the conduct in diffrent way insead of using the roof ??

thanks

Marc

p.s. please sized the ct and related fire pump system with locked rotor amps


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)


#64051 - 05/09/06 04:48 PM Re: Fire pump service  
Jps1006  Offline
Member
Joined: Jan 2004
Posts: 615
Northern IL
Mx,

Astute? yes, correct? not sure. (if it is possible to be astue and wrong at the same time.) Our local inspectors are fairly astute as well, and they disagree. Although the disconnect or not disconnect issue may be moot because for whatever reason the CT alone is only rated 10,000 AIC and with disconnect is 100,000 AIC.
Quote
sounds like this run will be well in excess of say, 25 feet or so...

No limit to length outside the building. Are thinking of a tap rule? Even those are allowed at unlimited length outside the building.

Bob,
I was under the impression the reference would be in NFPA 20. The NFPA website is pretty nice. They let me "thumb" through NFPA 20 for free and I couldn't find anything.

Marc,
The CT cabinet was going to be 10' from the transformer. Then up and over the building for roughly 100' total of conductor to the controller in the pump room which would have the disconnect. This way I save on not having to supply the disconnect and my grounds would be easier in the pump room.

The other options are to run 325' around the building with USE (oversized for VD) or through the building with MI cable or concrete encased RMC. Because the building is the net result of (3) seperate additions, it is not possible to get a clear shot through (concrete block stairwells, subbasements with different elevations), and I'm not interested in investingating how I would encase an overhead conduit run, properly support & form and cover. Even if I could, there is still not a clear shot.
Quote
p.s. please sized the ct and related fire pump system with locked rotor amps

I'm aware of the requirement to size the disconnect to locked rotor current, but not the requirement to size the CT cabinet to LRC.

Thanks for the input gentlemen.


#64052 - 05/09/06 09:01 PM Re: Fire pump service  
mxslick  Offline
Member
Joined: Oct 2004
Posts: 803
Atomic City, ID USA
Quote
I sure would like to see some code reference for that.

If the conduit is on the outside f the roof than the conduit is in fact outside the building in NEC terms.


I may have dropped the ball with that one, as I can't recall any Code reference as well. I'll brouse the book I've got ('99 edition) to figure out where I got the idea.

On a personal level though, thinking of how the metal, sparks and flames from a faulted conduit would in all likelyhood drop down upon the roof, it would still constitute a hazard IMO. (Thinking of the damage in the "4"RMC vs. Utility Current" thread)

I guess it depends on how one would look at the fact it's attached to the building, maybe? (But I agree, still qualifies as outside.)

Quote
No limit to length outside the building. Are thinking of a tap rule? Even those are allowed at unlimited length outside the building.


Most likely yes, I was thinking of the tap rule. Wouldn't a feeder to a fire pump technically qualify as a tap, since it is not part of the building's service equipment proper, and takes it's source prior to the building service disconnect? The mind wobbles... [Linked Image]

In light of your additional info, the rooftop is the most practical option here.


Stupid should be painful.


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