Fire Pump Wiring

[dvcraven052256]

I would like some input on what is requirement for 2 hour rated cables feeding a FP.

In essence what I have is an existing FP that is to be replace with new for a 30 story residential tower in St. Louis. The FP and all associated controls are located at the basement level. MY question is if 2-hour rated cable in required where I have highlighted?

I have attached a partial one line diagram for reference. The generator is located outside. I am thinking once I enter the basement level mechanical equipment room those conductors would require a 2-hour rated cable.

My other thought is since the FP service is fed from MSB-2 which is also located in the basement that maybe that portion of the cable would not necessarily require a 2-hour rated cable.

Your thought and consideration are most welcome. You may have to rotate the attachment to get the proper orientation.

Dan Craven

 

[Revous]

695.6(A)(2) should have your answer for the feeders coming from the generator and the normal side of the distribution.

 

[PD1972]

I agree the feeder between generator and FP ATS needs to be 2-hour rated (as you show it) for the portion inside the building.

The FP service doesn't look right. Is this a separate FP service with service conductors between the switchboard tap section and the FP ATS? If so, those conductors need to be installed per 230. Providing a 2hr cable doesn't satisfy the requirements of 230.6.

 

[Revous]

I agree the feeder between generator and FP ATS needs to be 2-hour rated (as you show it) for the portion inside the building.

The FP service doesn't look right. Is this a separate FP service with service conductors between the switchboard tap section and the FP ATS? If so, those conductors need to be installed per 230. Providing a 2hr cable doesn't satisfy the requirements of 230.6.

I didn't catch that! 695.3(A)(1) is the section that specifies that you can't have the FP tap in the same switchboard as the normal service, it has to be tapped ahead of the service.

Also take a look at 695.4 for disconnect and OCP sizing because the normal side OCP and emergency side OCP devices are sized differently.

 

[hillbilly1]

I didn't catch that! 695.3(A)(1) is the section that specifies that you can't have the FP tap in the same switchboard as the normal service, it has to be tapped ahead of the service.

Also take a look at 695.4 for disconnect and OCP sizing because the normal side OCP and emergency side OCP devices are sized differently.

The emergency side does not have to be sized for locked rotor, but many engineers will call for it to be tied ahead of the generator ocp. Doesn’t make any difference though, because cause the generator will shut down on overcurrent unless it is very large.

 

[PD1972]

I didn't catch that! 695.3(A)(1) is the section that specifies that you can't have the FP tap in the same switchboard as the normal service, it has to be tapped ahead of the service.

You can have a FP tap section in the same switchboard line-up as the normal service, it just needs to be its own separate vertical section and ahead of any service disconnecting means. Based on how the bussing is drawn on the riser, the tap is ahead of any circuit breaker.

 

[infinity]

Vita-link is 2 hour rated MC cable which is what everyone uses around here. 20 years ago it was always MI cable but those days seem to be over.

 

[dvcraven052256]

FP will have is its own section and yes the FP tap is arranged such that it will not be connected to the MCB.