Fire Pump Feeder

[kcunningham59]

Best way to feed a fire pump assuming a separate section isn’t included in the gear and the utility transformer can’t handle any more conduits. Man-hole with splice connectors? The service is 4,000A and I need to feed a 75 HP fire pump obviously ahead of the service disconnect

 

[Npstewart]

This is a 4000A service which means that it likely has a CT Cabinet in the building (assuming its not metered at the transformer).

Assuming the utility Co approved, why not turn the existing CT Cabinet into a large wireway and splice the existing service feeder to feed the Fire Pump service, and then re-feed a new CT Cabinet for the existing 4000A service?

 

[kcunningham59]

This is a 4000A service which means that it likely has a CT Cabinet in the building (assuming its not metered at the transformer).

Assuming the utility Co approved, why not turn the existing CT Cabinet into a large wireway and splice the existing service feeder to feed the Fire Pump service, and then re-feed a new CT Cabinet for the existing 4000A service?

Nothing is installed. But the gear is ordered with out a fire pump section. Is it feasible to hit a manhole after the transformer and splice in there and send one feed to the FP and then one to the metered/CT gear section


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[Npstewart]

Nothing is installed. But the gear is ordered with out a fire pump section. Is it feasible to hit a manhole after the transformer and splice in there and send one feed to the FP and then one to the metered/CT gear section


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It's feasible but this is entirely up to the power company. I had a project one time for an existing building where the existing service conductors between the Utility XFRMR and meter center were damaged by a saw blade, so we had to put in a hand hole to pull out the damaged conductors and we had to get special permission in writing from the power company to tap the existing service conductors.

Personally, I think the bigger issue could actually be voltage drop. Fire Pump feeders are required have a voltage drop of less than 15% under Locked Rotor Amp (LRA) Conditions. Assuming 208/3, the LRA of the 75HP fire pump would be about 1200 Amps, and then you have to add the demand amps of the non-fire pump loads to that.

What is the calculated demand of the "normal" loads on this service, and how far are you running?

FYI: If this is new construction then its probably a new transformer. The power co should be a able to put an additional cabinet next to the transformer to land additional conductors. The easiest thing may be to just email the power company.

 

[kcunningham59]

It's feasible but this is entirely up to the power company. I had a project one time for an existing building where the existing service conductors between the Utility XFRMR and meter center were damaged by a saw blade, so we had to put in a hand hole to pull out the damaged conductors and we had to get special permission in writing from the power company to tap the existing service conductors.

Personally, I think the bigger issue could actually be voltage drop. Fire Pump feeders are required have a voltage drop of less than 15% under Locked Rotor Amp (LRA) Conditions. Assuming 208/3, the LRA of the 75HP fire pump would be about 1200 Amps, and then you have to add the demand amps of the non-fire pump loads to that.

What is the calculated demand of the "normal" loads on this service, and how far are you running?

FYI: If this is new construction then its probably a new transformer. The power co should be a able to put an additional cabinet next to the transformer to land additional conductors. The easiest thing may be to just email the power company.

Yeah I guess on smaller services you could do a hand hole with an 8 or 12 port splice connectors but once you SE conductors start reaching 6+ sets you need to land on something with lugs, which assuming has to be done above grade and not ingrade.


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