Fire Pump Controller (VFD)

[ElecDar]

I have water pumps serving combined water\fire network.
In the Code (NFPA) the fire controller is allowed to start a motor while limiting the current drawn by the motor, the stipulation is that the starting period cannot exceed ten seconds.
My question is there any requirements in the Code which prohibit the use of a Variable Frequency Drive (VFD) as a fire pump controller?

Thanks in advance.

 

[dpc]

I don't know the answer, but it doesn't sound like a good idea, at least to me.

Aside from the added cost, the drive will reduce the overall reliability of the system.

I have never used a reduced-voltage starter on a fire pump and I have seen it only once before.

I would guess that the VFD would have to be part of a tested and labeled fire pump starter assembly and would be required to have a bypass contactor to start the fire pump across the line in the event of a failure of the VFD.

 

[busbar]

ElecDar, look over the functions and capabilities specified for fire pump controllers in '99 NEC Article 695. Also references Standard for the Installation of Centrifugal Fire Pumps, NFPA 20-1996.

I could have misunderstood all this, but with the restrictions in Article 695, I don’t think anyone could produce an NFPA 20-listed controller with a VFD.

 

[ElecDar]

dpc, I agree with you that it is expensive solution but the water pumps are serving a combined water\fire network, this is the main reason for installing the VFD to modulate the pump speed during normal operation based on varying demand in the domestic water system. This combined network is also serving external fire hydrants. Actually NFPA 20 (clause 7-4.5.2) allowed for the operation of reduced voltage controllers (acceleration not to exceed 10 sec.). Soft starter, Autotransformer, Wye-delta etc. Starters are already available, used before and they are all listed for fire service.

busbar, the only restriction I see in the NEC is that VFD should be listed for fire service which I’m not sure if it is available, other requirements could be met.

 

[dpc]

Why not just use a conventional starter to bypass the VFD for fire service? You would also need isolation contactor to isolate output of the VFD.

This would allow you to use the VFD for normal operation and still have a UL-listed fire pump controller for emergency service.

I don't know if this would be acceptable to local inspectors, or more importantly, your underwriter, but it get you a lot closer to a standard system.

dpc

 

[stevenal]

Seems like conflicting requirements. Domestic water pumps are installed under article 430, with the intent that that overloads and resulting fires are avoided. Fire pumps are installed under 695 with the idea that a motor giving its life in this capacity is desirable, since prevention is no longer posssible. Did the AHJ approve this installation, and which article prevailed?

 

[ElecDar]

dpc, that is my other option; actually I was trying to investigate the possibility of having VFD with failure mode cross line full voltage and listed for fire service but it seems it is not available yet.

 

[dpc]

Yes, no one is really interested in breaking new ground when it comes to heavily regulated items such as fire pump controllers. They just like to paint it red and mark-up the price about 100%. And they don't want the liability.

I hate to say it, but no one will give you much credit for being creative when it comes to fire protection system.

It might be less costly in the long run just to take the conservative brute-force approach.

You have to pick your fights, and you won't win any with a fire marshall.