Fire pump power supply on primary service 1

[ladengr]

I need some one to interpret what NEC requirements are for a fire pump power connections on a primary service distribution system.

This facility gets utility primary power service and the owner owns the 13.2 KV switchgear and transformer. The transformer supplies power to the building and the fire pump.
The fire pump is connected directly to the transformer secondary(480 Volts). The fire pump is also provided with emergency power from a diesel generator to meet the relaible power source.

Do we have need to coonect the pump ahead of the primary switch through its own transformer or is it ok to connect on the transformer secondary?
LADENGR

 

[rbulsara]

In my opinion you are in compliance with NEC, as you have it.

You surely do not have to go to the primary side. In fact, imho, you do no have to be on the line side of the LV main either if you have a generator as you describe it.

If you really want some kind of official interpretation, you can become a member of NFPA and ask for "informal" interpretation via a simple email and/or phone call. Getting a "formal" interpretation from NFPA is a drawn out process and probably expensive alternative.

But informal interpretation alone would carry a lot of weight compared to any other source.

 

[tommom]

From NFPA Digest, 2004:
"NFPA 20 permits combinations of power sources as follows:

Combination of two or more utility service or on-site power stations,
Combination of a standby generator and utility service or on-site power stations,
Combination of feeders from two or more power sources,
One or more feeders in combination with a standby generator,
Either a diesel engine-driven or steam turbine-driven fire pump."

If you have a main-tie-main auto-throwover arrangement in your switchboard secondary, you might be able to convince the AHJ that this is a reliable power source, or you may not. AHJ has the final say. If you've got a single primary feed with a single transformer and main, it's likely that can't be considered reliable, as it does not come from the utility transformer secondary stabs, and you might need a generator to back it up or use a diesel fire pump.

 

[dpc]

I think this installation is in compliance. Someone will have to explain to me how the installation magically becomes more reliable if the utility owns the transformer instead of the owner.

But of course, only one opinion matters, and it isn't mine.

But I've seen numerous similar installations (and much worse) that somehow passed inspection.

 

[davidbeach]

Main-tie-main won't meet the requirement that a fire at one service doesn't take out the ability of the other service to supply the fire pump. It takes a main-tie-tie-main system with three switchgear lineups in three rated rooms and the fire pump fed from the middle bus, between the ties.

 

[ladengr]

Thanks to DPC & RBULSARA for your valuable comments.

I just want you to know that the fire pump controller has an automatic transfer switch to transfer power from utility to generator in case of power failure or generator to utility when utility power is restored.

Do we meet the code, if we have power supply from the stand-by diesel generator to the pump with adequate on site fuel tank when the sprinkler system calls for the pump to start and no connections to the utility primary power source?

LADENGR

 

[rbulsara]

ladengr:
Answer to your last post is NO.

 

[dpc]

I agree - diesel generator alone is not sufficient.

 

[ladengr]

If so, it may make sense to go with diesel fire pump.

 

[rbulsara]

May be , may be not. Diesel engine driven pumps have their own issues.

A genset can be remote from the fire pump and the fire pump room and can be outside the building. Engine driven pump has to have the engine attached to it, so you need to address all issues such as air inlet, exhaust, louvers, etc that are applicable in an engine room.

You need to evaluate options based on your particular situation.

 

[dpc]

You may also want to consult your underwriters - they are often more interested in details of fire pump power supplies than are the local inspectors.

 

[gadero]

Don't believe that by the letter of the code, the proposed installation meets requirements. Best to check with the AHJ.

NEC 695.3 lists 2 acceptable individual sources...either a utility service connection ahead of the main (in the described case, the main would be the primary disconnect) or on-site power production. The AHJ decides if the connection is reliable. If the connection is not considered reliable, then 695.3(B)-Multiple Sources comes into play.

I'm assuming that your service isn't considered reliable by the AHJ. If it were, the fire pump feeder wouldn't comply with the requirements of 695.3(A) - Individual Services. The pump isn't connected ahead of the main.

Assuming that your single source isn't deemed reliable and your are planning on meeting the requirements of 695.3(B) "approved combination of one or more of such power sources in combination with an on-site standby generator..." you must still meet the requirements of an individual source - connect ahead of the main.

Best to check with the AHJ. I've seen approved installations with the fire pump feeder connected ahead of the transformer main secondary disconnecting means...similar to the described installation, but it was approved by the AHJ.

As far as some of the comments as to why to connect ahead of the main. Maybe someone with fire department experience can pipe in, but I thought the fire departments shut-down power to the building (open main) when fighting fires. Hence the requirement for connecting ahead of the main.

 

[rbulsara]

When a standby generator power is available, connection on line side of utility main is not required.

I do not have time and patience to post rebuttal to gadero's views.

 

[Joecurcio]

Can someone tell me if a standby genset used for a fire pump has to be dedicated to it or can other loads be connected also.

 

[l3city]

By experience, I think this is not a good idea, period. The premises shall be at no moment without power or depending on only one source of power. How about if there is a power outage for several hours and a fire starts (seems ridiculous, but can happen) The building safety (i.e fire alarm, fire pump, etc) shall always have access to power. My recommendation...use a stand-by generator with transfer switch.
Of course, this is just my opinion, with respect..

Answer to Joecurcio:
Yes, you can have other loads, as long you don't exceed the genset capacity. I've seen gensets running fire alarms, fire pumps, critical electrical panels, all at the same time (to keep computers running and security/emergency lighting, etc) Some designers have chosen to add a UPS (i.e. rechargable batteries) to keep everything running in case of a power outage.