Fire Pump Installation, FLC vs LRA

[Npstewart]

Hello everyone.

I am designing a new fire pump with a new 208-3 phase service to be put in a existing warehouse. I only have done one fire pump because typically, achieving the required flow without one isn't an issue.

The new fire pump will be 75 HP with a 1-1/2 HP jockey pump.

I pretty much have this thing wrapped up, however I have a big question.

According to the table in the NEC for a 208-3 phase load (75HP) the FLC is 211amps, however the LRA is 1200A!!! For some reason im reminded of a code that says the fused disconnect (one only) the fuses must be sized for LRA, however everything else can be sized for FLC. including the wire size.

AN overview of the installation
Right now, I have a new service going to the exterior (3) #600s +Ground, then it goes to a 1200A fused disconnect, from there it goes over head to the fire pump controller (the run is with RHW wire by the way).

There is no way I could size the service for 1200A. The fire pump controller that is specifically made for the 75HP pump will only accept up to a certain wire size, it certainly wont accept a 1200A feeder.

Any help with this would be greatly appreciated.

 

[Volta]

The new fire pump will be 75 HP with a 1-1/2 HP jockey pump. . .

According to the table in the NEC for a 208-3 phase load (75HP) the FLC is 211amps, however the LRA is 1200A!!! For some reason im reminded of a code that says the fused disconnect (one only) the fuses must be sized for LRA, however everything else can be sized for FLC. including the wire size.

AN overview of the installation
Right now, I have a new service going to the exterior (3) #600s +Ground, then it goes to a 1200A fused disconnect, from there it goes over head to the fire pump controller (the run is with RHW wire by the way).

There is no way I could size the service for 1200A. The fire pump controller that is specifically made for the 75HP pump will only accept up to a certain wire size, it certainly wont accept a 1200A feeder.

Any help with this would be greatly appreciated.

I can't tell if your pump is planned to be a separate service, but it needs to be connected to the line side of the regular service, and not in the disconnect enclosure. 695.3.
If you are using a service rated controller for the 75 hp, I would think that it would be sized for the correct OC device to be installed.
If it is not service equipment, you will need the remote disconnect, with OCP.
Let's see: 75hp LRA is 1200 + 1.5hp say 3ph is 44 LRA + accessory equip say 10 amps? = 1254 amp min fuses or breaker.
So I think you either need a smaller pump, or a service enclosure greater than 1200 amps. You can probably still feed it with 300 kcm or so, but don't forget the voltage drop limits of 15 and 5%. 695.7.

 

[bob]

According to the table in the NEC for a 208-3 phase load (75HP) the FLC is 211amps, however the LRA is 1200A!!! For some reason im reminded of a code that says the fused disconnect (one only) the fuses must be sized for LRA, however everything else can be sized for FLC. including the wire size.

695.4 says The overcurrent protective device shall be set to carry indefinitely the sum of the lock-rotor current of the fire pump and other equipment. The requirement to carry lock-rotor current shall not apply to the conductors or devices other than the overcurrent devices in the fire pump circuit. The conductor shall have a rating of 125% of the pump motor + other motors + 100% of the associated equipment. 75 HP FLA
equal 211 amps + 1.5 HP 7 amps = 218 x 1.25 = 273 amps.
In other words you do not need a 1200 amp service.

 

[Volta]

True, but from this info the OP needs a service-rated disconnect greater than 1200 amps.

 

[bob]

True, but from this info the OP needs a service-rated disconnect greater than 1200 amps.

Why is it so?

 

[Npstewart]

Fire rated Cable

Fire rated Cable

To make matters a little more inconvienient for me, I have another predicament!

According to Article 695, the jockey pump (pressure maintenance pump) must be TAPPED in before the fire pump controller. Obviously it would be wise to do this right before the controller. However because my feeder needs to be fire rated, if I tap the feeder it will compromise the (2) hour rating.

I was originally going to use RWH cable which is two hour rated, but has anyone ever heard of a (2) hour rated conduit I could use, and then use a (2) rated junction box with standard cable?

Thanks for your help in advance, more opinions the better

 

[bob]

NP
Check here for more information http://ecmweb.com/nec/code-basics/electric_code_basics_17/

 

[Volta]

Why is it so?

To house the OCP required as a service by 695.3(A)(1)>230.90, or 695.4(B)(1), and by 695.6(D).

To make matters a little more inconvienient for me, I have another predicament!

According to Article 695, the jockey pump (pressure maintenance pump) must be TAPPED in before the fire pump controller. Obviously it would be wise to do this right before the controller. However because my feeder needs to be fire rated, if I tap the feeder it will compromise the (2) hour rating.

I was originally going to use RWH cable which is two hour rated, but has anyone ever heard of a (2) hour rated conduit I could use, and then use a (2) rated junction box with standard cable?

Thanks for your help in advance, more opinions the better

Are you sure the about the maintenance pump? I don't think you need to do that, what section do you mean?

 

[Volta]

Bob, looking at the link you provided, I read that Sec. 7-1.2.4 in NFPA 20 requires all FP controllers to be service rated. So a remote disconnect may not be needed after all, if the supply conductors are run in concrete to be considered "outside of a building". 230.6.

 

[don_resqcapt19]

...

According to Article 695, the jockey pump (pressure maintenance pump) must be TAPPED in before the fire pump controller. Obviously it would be wise to do this right before the controller. However because my feeder needs to be fire rated, if I tap the feeder it will compromise the (2) hour rating. ...

There is nothing in Article 695 that says the jockey pump must be tapped in before the fire pump controller. As a matter of fact, Article 695 does not even cover the jockey pump. It is wired like any other motor per the rules in Article 430.

695.1 Scope.
FPN: Rules that are followed by a reference in brackets contain text that has been extracted from NFPA 20-2007, Standard for the Installation of Stationary Pumps for Fire Protection. Only editorial changes were made to the extracted text to make it consistent with this Code.
(A) Covered. This article covers the installation of the following:
(1) Electric power sources and interconnecting circuits
(2) Switching and control equipment dedicated to fire pump drivers
(B) Not Covered. This article does not cover the following:
(1) The performance, maintenance, and acceptance testing of the fire pump system, and the internal wiring of the components of the system
(2) Pressure maintenance (jockey or makeup) pumps

 

[Volta]

There is nothing in Article 695 that says the jockey pump must be tapped in before the fire pump controller. As a matter of fact, Article 695 does not even cover the jockey pump. It is wired like any other motor per the rules in Article 430.

While 695(B)(2) does say that, other sections such as 695.4(B)(1) and 695.5(B)(1) do make reference to jockey pumps and require us to include those motors in the LRA for OCP selection.

Room for clarification by CMP 13, though I won't hold my breath.

 

[don_resqcapt19]

While 695(B)(2) does say that, other sections such as 695.4(B)(1) and 695.5(B)(1) do make reference to jockey pumps and require us to include those motors in the LRA for OCP selection.

Room for clarification by CMP 13, though I won't hold my breath.

Yes, they are mentioned in a "permissive" manner. They are permitted to be connected to the fire pump power supply and these sections only tell you how to size the fire pump power supply if you use that as the source of power for the jockey pump. It does not tell you how to wire the jockey pump. The rules 430 do that.

 

[Volta]

Gotcha. So if the OP has a remote service disconnect, and only serves the fire pump controller, at LRA of 1200, are 1200 amp fuses big enough? There must be some load associated with the controller.

Or, if the controller is the service disconnect, is it likely to already have provisions for acceptable OCP?