How to size Fire Pump based on Incoming Electrical Service

Status
Not open for further replies.
E

Electricalhelp

Senior Member
Location
NJ
The current building has 800 AMP/208V/3 Phase service.
The existing drawing is calling for a 10-hp Fire Pump with a 1/2-hp jockey pump with a OCPD OF 200 AMP
But the project manager told me the lead time for the 10-hp motor is 6 to 8 months.
The PM, recommend installing a 15-hp motor?

The 10-hp and 1/2-hp OCPD [200.1A to 200 AMP LRC] AND FLC [33.2A]
The 15-hp and 1/2-hp OCPD [ 279.1A to 400AMP LRC] and FLC [48.6A]

Will the 80AMP effect the incoming electrical service size? Do I need to increase the incoming electrical service to accommodate the new pump.
The total building demand is about 700 AMP.
 
Does the 700 amp calculation already include the fire pump? If so you're only adding about 15 amps.
 
You have to size it for the 15 hp motor size. The 10 hp load is irrelevant. If this is a legally required fire pump, it has to served separately from the normal service.
 
You are adding 15 amps the the service conductors from CT to service point. What size are those conductors?

Also are the 10 hp and 15 hp fp controllers the same size?
Are the pump curves for 10 and 15 hp similar? Is the higher head on the 15 hp ok?
 
tom baker said:
You are adding 15 amps the the service conductors from CT to service point. What size are those conductors?

Also are the 10 hp and 15 hp fp controllers the same size?
Are the pump curves for 10 and 15 hp similar? Is the higher head on the 15 hp ok?
Click to expand...
I will upgrade the size of the conductors for the 15 hp motor.

David Castor said:
You have to size it for the 15 hp motor size. The 10 hp load is irrelevant. If this is a legally required fire pump, it has to served separately from the normal service.
Click to expand...
The connection is ahead of the service disconnect.
 
I think the electrical system should be modelled (like in SKM) for determination of compliance with 695.7 Voltage Drop for Fire Pumps. I would expect that since you're on an 800-amp service it could start a 15 hP motor, but if you could show a maximum starting voltage drop of 15% and a running drop of 5% you would meet the NEC criteria.
Modelling of the system would include contact with the Utility source for determination of their fault contribution and ocpd.
 
This is not the kind of thing that you can just arbitrarily go from 10 HP to 15 HP without the EOR blessing. Also most AHJs would require plan resubmittal for a change like this.
Is the pump curve acceptable for the application?
Depending on the voltage this may require a larger FP controller.
Will it affect VD calcs for the FP?
 
mayanees said:
I think the electrical system should be modelled (like in SKM) for determination of compliance with 695.7 Voltage Drop for Fire Pumps. I would expect that since you're on an 800-amp service it could start a 15 hP motor, but if you could show a maximum starting voltage drop of 15% and a running drop of 5% you would meet the NEC criteria.
Modelling of the system would include contact with the Utility source for determination of their fault contribution and ocpd.
Click to expand...
I got the same wire size as continuous load and Voltage drop of 15%.
This calculation was only for the 15 hp motor.
So i need to size the wire pump with #6

I need to determine the building demand load and include the fire pump to see if the 800 AMP can handle the new pump.

Screenshot 2023-12-28 211742.png
 
Electricalhelp said:
I need to determine the building demand load and include the fire pump to see if the 800 AMP can handle the new pump.
Click to expand...
You really should feed the fire pump with a separate service from the utility transformer if you can. Get the fire pump supplier to provide a service rated fire pump controller, or a service rated, transfer switch, fire pump controller if you have a generator. Keep the service conductors outside the building until they enter the fire pump room. This approach will save you a ton of headache dealing with the quantity of disconnect limitations, sizing the overcurrent to handle locked rotor current, conductor requirements, and all the other requirements of Article 695.
 
As others have alluded to, I will make explicit. Do you have a sign-off from the company/engineer that is responsible for sizing the fire pump? There's going to be a bunch of changes, not the least of which is the outlet pressure of the pump. You could easily exceed the design for the pipe and fittings.
 
Status
Not open for further replies.
Top