Smoke Control power monitoring

[Kingswillfall]

I have to provide “positive confirmation” according to NFPA92 sec 6.4.8.2. The presence of power for a dual zone smoke control system. VFDs are housed inside with local disconnects at the fans (outside). Power monitoring must be downstream of all circuit disconnects. This means load side of the last disco and the fan motor. My dilemma is that the system is only powered when commanded by Fire Alarm input to the VFDs. How do I show status without power downstream of the disco and still meet the requirement?

 

[Jraef]

Don’t know that NFPA section, but this is what AI said it says:

NFPA 92 Section 6.4.8.2 requires that the loss of normal power to a smoke control system's dedicated power supply equipment be supervised by the fire alarm control unit
. This monitoring ensures that any failure of the primary electrical source for the smoke control system is immediately detected and reported.

Highlight added.

So to my reading, that means you just have to monitor the SOURCE, not the actual load power. So a voltage monitor relay on the switchgear/switchboard that is supplying the dedicated circuit for all of this.

 

[gadfly56]

^^^^^What he said!

 

[Cursitti]

Don’t know what type of drive you have but I’ve been able to monitor power loss on most HVAC equipment with a fire alarm monitor module and a set of NO contacts within the equipment when equipment is powered down monitor module sees a short across resistor and will notify main FACP. or you can use a voltage monitor relay as stated above.

 

[herding_cats]

Don’t know what type of drive you have but I’ve been able to monitor power loss on most HVAC equipment with a fire alarm monitor module and a set of NO contacts within the equipment when equipment is powered down monitor module sees a short across resistor and will notify main FACP. or you can use a voltage monitor relay as stated above.

That's exactly what I do. Really simple and works.

 

[SantaFebuff]

Don’t know that NFPA section, but this is what AI said it says:

Highlight added.

So to my reading, that means you just have to monitor the SOURCE, not the actual load power. So a voltage monitor relay on the switchgear/switchboard that is supplying the dedicated circuit for all of this.

Definitely need to monitor power source, but according to the annex material this standard section is aimed at verification of the system functionality entirely.

"Annex A - Explanatory Material,
A.6.4.8. The means and frequency of verification methods will vary according to the complexity and importance of the system as follows:

• (1) Positive confirmation of fan activation should be by means of duct pressure, airflow, or equivalent sensors that respond to loss of operating power, problems in the power or control circuit wiring, airflow restrictions, and failure of the belt, the shaft coupling, or the motor itself.
• (2) Positive confirmation of damper operation should be by contact, proximity, or equivalent sensors that respond to loss of operating power or compressed air; problems in the power, control circuit, or pneumatic lines; and failure of the damper actuator, the linkage, or the damper itself.
• (3) Other devices, methods, or combinations of methods as approved by the authority having jurisdiction might also be used."

Unfortunately, I do not have a lot of experience on fire circuits. I'll try to recommend something with my last two braincells, and you can let me know if this sounds correct or someone else here will likely check me. The good news is, all of this is looking at confirming operations - so not sure if it being unpowered normally is even an issue. I think this ties back into your regular testing and documentation of system functionality through that testing. To me, it reads that you would just need to prove things are working, when they are supposed to be working.

Breaking down the first bullet point, you would want to focus on mechanical and electrical. Mechanically, I'm thinking a supervised air flow switch that should work, maybe add a pressure switch? Electrically, I'm thinking a current output switch/relay or the above mentioned drive output to a fire module. I can't argue with that idea, I don't work enough on fire panels.