Fire Pump Circuit

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dvcraven0522!

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Electrical Design
I have attached a a one line sketch showing utility xfrm. feeding a MDP with full generator back up.

It is my understanding I am allowed to feed a fire pump circuit as shown on the CB #1 from the MDP as shown. The only requirement is that this circuit breaker shall carry the the locked-rotor current of the FP motor. But the conductors to this FP are only require to be sized for 125% of the FP motor FLA. Is that correct?

Thanks
Dan Craven
 

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  • Sketch One Line.pdf
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The one-line you have shown has quite a few issues. The ATS will need to be a service rated ATS, which means you will have too many disconnects ahead of the fire pump, among other issues.

Save yourself a ton of headache and get a service rated, ATS fire pump controller. Get two output breakers in your generator, one for your building ATS and one for your fire pump controller. Bring two service laterals from your utility transformer, one for your building ATS, and one for your fire pump controller.
 
There is a good Standard at

Application Guide for Electric Fire Pump Controllers​

Application Guide for Electric Fire Pump Controllers
www.nema.org
www.nema.org
 
dvcraven0522! said:
Could I not provide a FP tap section in the MDP?
Click to expand...

NEC Article 695.3

The connection must be ahead of, and not within the same cabinet, enclosure, switchgear section, or switchboard section as the service disconnecting means. The objective is to minimize the possibility of fire damage to the fire pump feeder. Keeping it out of the electrical service equipment is an effective means to achieve that.
 
dvcraven0522! said:
Could I not provide a FP tap section in the MDP?
Click to expand...
Not with a service rated ATS ahead of the MDP. There is a breaker in that transfer switch, and you are adding a breaker in MDP ahead of the fire pump. 695.4(B)(1) limits you to one disconnecting means. Your design has at least two.

Also, I would be very surprised if the power company would let you meter on the load side of that ATS.
 
A few comments on the revised sketch:
  1. The fire pump ATS could be part of the controller. I would strongly recommend getting that in lieu of providing a separate ATS. That puts the sizing for all of the fire pump related equipment on the fire pump manufacturer and removes the risk from your plate.
  2. The utility meter will need to be ahead of your transfer switches. The exact requirements will depend on your utility company. Some will meter at the transformer and some will make you provide a CT cabinet for the metering.
 
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