Fire Pump

A wild guess. Maybe they don't mind burning up the pump, but they don't want to burn up the generator. That could get pricey.

The intention is so the generator does not overload due to the fire pump smoking away as the generator also supports other life safety necessities such as elevator, emergency lighting, fire alarm AOR, ect.

That may be it, Thanks

I have a partial one-line showing the wiring for fire pump/generator/normal power layout.

I tried to post it within my response but the file may be too large.

If you want me to e-mail the one-line to you, shoot me a PM.

Good Luck!

How else you wish to avoid paralleling of mains with the generator.

What would be arrangement if many fire pumps (say 04) are put on same bus.

In plant i worked we had 4 fire pump with breakers and each getting starting signal at different water pressure.

With arangment as asked by guest all fire pump (04) would start simultaneously? if one pump burn it would trip generator tripping all pump.

if this is a ul listed panel the breaker is on the normal side not emerg. It is also not just a breaker it is a locked rotor protector.

If the generator capacity is 125% greater than pump a lrp should be here also as per NFPA20

Here are some of the rationales, but check your local code requirements.

A motor can run slightly overloaded for quite a while before it will burn up. In the case of fire pumps, it is deemed best to run the pump to failure rather than stop it on an overload. (Putting out the fire is more important.) Thus motor overload heaters/relays are not installed.

If there is a short circuit, however, that could start another fire or even bring down a genset. Therefore there should be short circuit protection (breaker or fuses). I think there is a different sizing calculation so that the breaker opens at or near locked rotor current. And maybe wire size calculation also. (At least it would make sense to use "oversize" wiring.)

The pump itself should be selected to have non-overloading impeller trim, even at the far right of the pump curve. A motor service factor >1.00 might also be good; I'm not sure if it is required.

More than one code may apply, such as both NEC and NFPA in the U.S. Once again, check your local jurusdiction(s).