Fire alarm raceway requirement

[peter d]

I used to live in a state that has an all-metal raceway requirement for fire alarm conductors (EMT, RMC, IMC, FMC and Wiremold). Thankfully, MC cable is also permitted.

Is there any evidence that metal raceways have better survivability in a fire?

I would think that heating up a raceway with fire will just as quickly destroy the conductors inside as a non-metallic cable assembly.

I have heard the smoke contribution argument (with respect to the use of cable), but aren't FA cables allready required to be low-emission?

When a fire starts raging, does any wiring method short of MI cable stand a chance?

[ January 22, 2005, 11:23 PM: Message edited by: peter d ]

 

[peter d]

Re: Fire alarm raceway requirement

Hmmm.....no takers?

 

[ron]

Re: Fire alarm raceway requirement

I would suggest that metal raceway does not effect the survivability due to heat of a standard fire alarm cable. It surely would help survivability due to physical damage.
If your concerned about survivability due to heat, check CI and CIC cable

 

[peter d]

Re: Fire alarm raceway requirement

After further research, it appears that metal raceways do not provide anything near a 2-hr rating as prescribed by NFPA 72.

The CI cable does have a 2-hr rating.

I think the raceway requirement has more to do with giving electricians more work than it does with increasing safety. :roll:

 

[Nick]

Re: Fire alarm raceway requirement

Some reps pushing vitalink circuit integrity cable came in a few years ago and had some interesting video. In laboratory tests it showed that cable inside conduit burned up faster than the same cable without conduit. The conduit has an oven effect increasing the temperature of the cable making it fail faster.

 

[peter d]

Re: Fire alarm raceway requirement

Thanks Nick. That further confirms my suspicions.

 

[oliver100]

Re: Fire alarm raceway requirement

Who needs a fire alarm when a fire is going on?

May be the reason for metal conduits requirements is a phisical damage protection.

 

[peter d]

Re: Fire alarm raceway requirement

Originally posted by oliver100:
Who needs a fire alarm when a fire is going on?

There are many reasons why fire alarms are required. Preservation of human life is first and foremost among them.

But, you do raise an interesting point. By the time the alarm is going off, and flames are raging, there could be very little time to escape.

There is no one living at a Lowe's or Walmart at night, and in that case, the FA system is strcitly there to alert the FD and save the building.

By day, it is there to alert the shoppers to get the heck out, but with a wide open place like those, hopefully people would get the idea if they saw one of the aisles on fire.


There is a lot of psychology involved with FA systems. Most people ignore the alarms unless they actually see flames and see or smell smoke.

This is why they sweep dormitory rooms after a fire alarm, to make sure all the students are out. Most will just stay in their rooms and ignore the alarm, because dormitories and the like have so many false alarms. False alarms totally destroy people's confidence in FA systems.