Staircase Pressurization Fan Motor Overload

[janagyjr]

No, you are not comparing apples to apples, 410.136(B) specifically allows the installation per the manufacturers listing and labeling / instructions and has wording for this.



Can you provide another article section which will specifically allow the topic at hand?

Roger

relevant bit of 430.31:
"These provisions shall not require overload protection where a power loss would cause a hazard, such as in the case of fire pumps."

 

[roger]

relevant bit of 430.31:
"These provisions shall not require overload protection where a power loss would cause a hazard, such as in the case of fire pumps."

And I agree with you that in this case that is the relevant section.

Roger

 

[janagyjr]

So if a fan is being used to evacuate smoke in an emergency situation, bypassing the overloads would be okay with the code because if the overloads tripped off, it would create a hazardous situation, just as if the water stopped pumping from a fire pump.

 

[roger]

So if a fan is being used to evacuate smoke in an emergency situation, bypassing the overloads would be okay with the code because if the overloads tripped off, it would create a hazardous situation, just as if the water stopped pumping from a fire pump.

IMO yes but, unlike the Fire Pump example, all inspectors may not interpet stairwell pressuration as important.

Roger

 

[janagyjr]

*nods* I could see that, I've heard some horror stories about how qualified some inspectors are to begin with at other discussion places located on the Internet so one who doesn't understand stairway pressurization wouldn't surprise (nor horrify) me, at least in this case. At the very least hopefully the OP can make an informed decision and be ready to defend it (whether or nor it does any good to defend it is another case entirely).

AND I've learned something in the process (mainly that because it says one thing in some part of the code doesn't necessarily mean it applies to all of it, though I would have thought 110.3(B) would have been sufficient I am apparently wrong about that).

 

[Twoskinsoneman]

I'm no fire expert but isn't a smoke purge system something that happens after the emergency is over? I mean you wouldn't want all that air moving a possible fanning the flames right? Just curious

 

[janagyjr]

I don't know. I wouldn't want the smoke to remain in the stairwells if that's the only means of evacuation. I'm not versed in fire codes either. He was asking about the NEC portion of it. Let him go to a Fire Marshall to ask about that (and that is something to be asked about).

 

[roger]

I'm no fire expert but isn't a smoke purge system something that happens after the emergency is over? I mean you wouldn't want all that air moving a possible fanning the flames right? Just curious

Smoke purge, smoke evac, and pressurization is a neccessity in OR's during the emergency, the doctors have to be able to close a proceedure. This confines the air flow and air movement to an area isolated from the flames.

Roger

 

[don_resqcapt19]

relevant bit of 430.31:
"These provisions shall not require overload protection where a power loss would cause a hazard, such as in the case of fire pumps."

I missed that section and the application of that section along with the instructions would permit the overloads to be omitted. Thanks

 

[janagyjr]

No, thank you for allowing me to participate in this discussion. I spent 30 minutes digging in my code book for that bit (what's sad is I went over it several times looking at other parts of 430). I wound up using the index out of frustration and as a result am more familiar with my book.

 

[gadfly56]

I'm no fire expert but isn't a smoke purge system something that happens after the emergency is over? I mean you wouldn't want all that air moving a possible fanning the flames right? Just curious

Yes, but the same fans used for purge may be used for pressurization (stairwells, elevator shafts). The difference is usually how the dampers are set. So in the pressurization mode, you could bypass, but in the purge mode you couldn't. I'm not an expert on smoke control, but it is also possible that the purge operation is considered a potential hazardous situation as well.

 

[sccat]

NFPA 92A-2006 Standard for Smoke-Control Systems Utilizing Barriers and Pressure Differences

Annex D Fire Fighters? Smoke-Control Station Considerations

Control actions issued from the FSCS should not override or bypass devices and controls intended to protect against electrical overloads, provide for personnel safety, and prevent major system damage. These

 

[sccat]

Is "Staircase Pressurization Fan " a part of "Smoke-Control Systems"?

 

[janagyjr]

NFPA 92A-2006 Standard for Smoke-Control Systems Utilizing Barriers and Pressure Differences

Annex D Fire Fighters’ Smoke-Control Station Considerations

Control actions issued from the FSCS should not override or bypass devices and controls intended to protect against electrical overloads, provide for personnel safety, and prevent major system damage. These

That says from the fire safety control system (assuming that's the expansion for FSCS). I don't think the OP is suggesting that the controls bypass it, but the power wiring itself. 430.31 will allow for such overloads to be bypassed (legally) if it's considered part of a system necessary for safety "such as a fire pump." If the argument can be made for the pressurization system being necessary for safety in a fire...the OCPD will still be in the circuit.

 

[weressl]

I don't know. I wouldn't want the smoke to remain in the stairwells if that's the only means of evacuation. I'm not versed in fire codes either. He was asking about the NEC portion of it. Let him go to a Fire Marshall to ask about that (and that is something to be asked about).

Your OP stated that the fans are used for pressurizing the staircase. In that case - no pun unintended - the fans are installed to keep smoke OUT of the staircase, the positive pressure would 'drive' the smoke back to its source to provide an escape route smoke-free. If you have an overload situation it could be that the original leakage through the various openings are is less than the original design estimated. The crude way to overcome this is to install gravity louvers to relieve overpressure and resulting overload. The efficient way is to install a differential pressure controlled ASD that spins low when all openings are closed and spins up as the doors are opened. Should you judge this to be a fire safety item, you would still want to rethink the omittance of the OL protection unless this fan only pressurizes the staircase when it is triggered by the FA system. (If the fan continuously pressurizes the staircase,not only during fire, then you may install redundant fans and alarms on overloadtrip and/or pressure loss.)

 

[don_resqcapt19]

i would expect that these fans would be of centrifugal type and a higher pressure in the protected area as result of reduced air flow would result in a lower current.

 

[weressl]

i would expect that these fans would be of centrifugal type and a higher pressure in the protected area as result of reduced air flow would result in a lower current.

Correct, dyslexic thinking, the overload may occur if there are too many doors open.