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Sprinkler (Fire) Pumps - Generator Secondary Supply

Good afternoon.

I am currently working on the design of a 5 storey commercial building equipped with a sprinkler system.

The sprinkler pumps will naturally be provided with a secondary supply, which in our case will be via a diesel generator.

While sizing the generator, i was advised by the pump manufacturers that the generator needs to be sized based upon the Locked Rotor Current + Starting Current of the

sprinkler pump as per BS 12845 and LPC Rules for automatic sprinkler installations TB210.

I checked BS 12845 (2015+ A1:2019) and TB210 (2009 - don't have the 2015 edition), but couldn't find anything clearly confirming the above.

I have also seen references to NFPA 20 and specifically 695.3 which states that generators should be selected with sufficient capacity (kW) to permit the normal starting and running of the motors in the fire pump system -- plus all other connected loads.

Does anybody have any relevant experience on the matter? Do i really have to provide a generator for the LRC + SC? Any ways around it?

I would appreciate your thoughts.

Thank you in advance for your help.

Ilias

0 Former Community Member over 5 years ago

The generator needs to be able to handle the starting of the fire pump and still provide adequate voltage

It's pretty normal to size the set based on the pump locked rotor current at a 15% volt drop - plus any other loads the gen set supplies, and to close those loads in within 10 Seconds

Basically you are treating the fire pump and generator combination as a run to destruction system providing life safety

If the generator is solely for the fire pump, it's often more efficient to provide a secondary diesel engine direct drive fire pump instead of the generator. Often you have the motor, pump and diesel engine on the same shaft, with a clutch - if the motor doesn't get the pump running (loss of mains as an example), the diesel engine starts and takes over and usually does get the pump running

In my experience, yes, you will have to comply and the generator set is often frighteningly large (particularly if it wasn't accounted for in early design stages) when supplying fire sprinkler pumps and similar

Regards

OMS
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0 fiftyhertz over 4 years ago

Sorry to dig up an old thread OMS, but if I have a Fire pump with a 900A LRC would the base generator size really be 620KVA + all my other loads. Doesnt seem quite right, and as you say the generator would be enormous.
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0 Former Community Member over 4 years ago

Chris Dixon

Technical & Sales Manager

Fire Suppression Solutions

Ceasefire Industries UK Ltd
chris@ceasefire.co.uk

07716 642072
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0 ilias over 4 years ago

Hi,

It will probably need to be bigger than that as you will need to additionally consider the SC of the secondary fire pump...

I would speak with a generator manufacturer if i was you. Tell them your loads and they should be able to size the generator for you.
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0 Former Community Member over 4 years ago

Have a chat with Chris, details in previous post, who will discuss your overall system requirement and provide advice.
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Sprinkler (Fire) Pumps - Generator Secondary Supply

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