Can I fit an on-delay to a fire pump?

[ColinMacPhail]

Hi,

I'm looking for a bit of guidance as to if it would be accepable for me to fit an electronic on-delay timer to a desiel fire pump?

Our system comprises of 2 jockey pumps, an electric and a desiel.

My problem is that we occasionally have pressure drops and it takes a few seconds for the jockeys to recover.
This is bringing on the electric and sometimes the desiel.

Because of the nature of the water system, I am unable to reduce the drops, so the easiest solution would be to fit a delay-on timer set to 3-5 seconds, this would cure it.

I'm just not sure of the legality of doing this as it is a crittical piece of safety equiptment.

Any help or advice would be appreciated.

Regards, Colin

 

[rbulsara]

Most likely yes, but you need to check NFPA first. I believe it specifies maximum time delay for water flow detection and notification. But to be on the safer side I would also let the local fire marshal know of the arrangement.



Rafiq Bulsara

http://www.srengineersct.com

 

[LCREP]

From an insurance AHJ point of view. I agree it is OK to delay the start. The only problem I see it the water hammer caused by the delay and pressure drop. The other option is to use the a flow switch to start the pump, see below from NFPA 20, 2010. I would also check with your insurance carrier if you have one, to see what they think, since they get to pay the claim!

10.9.2 Automatic Starting. In lieu of the pressure-actuated
switch described in 10.5.2.1, automatic starting shall be capable of being accomplished by the automatic opening of a closed circuit loop containing this fire protection equipment.

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Fire Sprinklers Save Firefighters’ Lives Too!

 

[NJ1]

LCREP suggested a great option of starting fire pump with flow device instead.
However if you are looking to fit an electronic delay timer
(I assume at the controller panel) you must contact the panel manufacturer. It could void warranty on panel. Have them come and analyze options before you contract anybody to do so.
Your insurance carrier must approved such alteration.

 

[ColinMacPhail]

Thanks for the advice.

I think I'll get the OEM involved as the pump is fairly new.

Regards, Colin

 

[chillylulu]

Colin,

You stated:

"Our system comprises of 2 jockey pumps, an electric and a desiel.

My problem is that we occasionally have pressure drops and it takes a few seconds for the jockeys to recover.
This is bringing on the electric and sometimes the desiel."


NFPA 20, 2007 states:

"5.24* Pressure Maintenance (Jockey or Make-Up) Pumps.

A.5.24 Pressure maintenance (jockey or make-up) pumps should be used where it is desirable to maintain a uniform or relatively high pressure on the fire protection system. A jockey pump should be sized to make up the allowable leakage rate within 10 minutes or 1 gpm (3.8 L/min), whichever is larger.

5.24.1 Pressure maintenance pumps shall have rated capacities not less than any normal leakage rate.

5.24.2 The pumps shall have discharge pressure sufficient to
maintain the desired fire protection system pressure."

& later:

"5.24.6 The primary or standby fire pump shall not be used as a pressure maintenance pump."

It sounds like either your jockey pumps are not sized appropriately, your check valves are not working properly, something is not installed properly, or the pressure switch settings are not set appropriately.

You have some latitude in setting the on/off settings of your fire pumps and the jockey pumps. Assuming that the fire pumps are installed parallel, I would set the diesel cut-in 10 PSI higher than the electric pump.

The system pressure should not be fluctuating that much, unless there are non-fire protection system connections or some kind of outflow. System check valves should lock the jockey pressure in, which should be set as follows:

NFPA 20, 2007 A.14.2.7
"(4) Fire Pump Settings. The fire pump system, when started by pressure drop, should be arranged as follows:
(a) The jockey pump stop point should equal the pump churn pressure plus the minimum static supply pressure.
(b) The jockey pump start point should be at least 10 psi(0.68 bar) less than the jockey pump stop point.
(c) The fire pump start point should be 5 psi (0.34 bar)less than the jockey pump start point. Use 10 psi (0.68 bar) increments for each additional pump."

If you are the owners representative, you should have someone train you on the proper maintenance of your pumps.

By the way, the pumps are probably set to run automatically at regular intervals. This is especially true of diesel pumps.

Good Luck!

 

[chillylulu]

& 1 more thing...

LCREP

Doesn't 10.9.2 refer to additive pumps only? I have never seen (having performed 100's of fire pump tests over 28 yrs.) a NFPA 20 type pump start off of a flow switch - rather they use pressure switches. An additive type pump is for introducing something into the water flow. I have seen these used on foam and on MIC inhibiting systems.

Regards.

 

[NJ1]

Chillylulu I have seen couple of set up's where a paddle type flow device or pressure sensing device activates the fire pump but you are right technically a pressure switch is a better option because it works as a mercoid switch.

 

[b1ueshift]

I would suggest you find another way. You could modify the control system, but you probably shouldn't. You can't modify the panel without voiding the UL listing conditions of the panel and you can't rely on flow switches or remote pressure sensors to start the pump and still comply with NFPA 20.

Why are you getting pressure fluctuations? Don't you have check valves in your system to maintain the pressure when the supply pressure falls?