Fire alarm cable in flex?

[kbsparky]

I have a client with an elevator/electrical room that has a couple of smoke detectors mounted on the ceiling.

The ceiling is about 15 feet high, poured concrete. There are a total of nine(9) recessed cavities in this ceiling, about 18 inches deep or so. They look like mini-alcoves from the floor.

Along comes a state elevator inspector, and now he wants us to install a smoke detector inside of =each= of these recessed alcoves in the ceiling.

Aside from the logistical problems of erecting and moving scaffolding to accomplish this task, it appears that installing a flex type cable (MC?) would be an easier task than using EMT and individual conductors. Lots of bends to get in and out of each of these alcoves.

Can I install some riser type multi-conductor fire alarm cable into greenfield for this type of installation? It might simplify things a bit ...

 

[PEDRO ESCOVILLA]

is this concrete ceiling what is rerferred to as a "waffle slab". it looks like a waffle only a lot bigger. i've always been under the impression that one smoke detector was required at the top af an elevator shaft. , but i digress, yes i don't see why you couldnt use greenfeild to accomplish the task at hand.it looks good per 620.21 in the NEC

 

[iwire]

Keep in mind flex is limited to 360 degrees just like EMT.

On the other hand you could just use fire alarm MC cable with as many bends as needed.

 

[nhfire77]

Fire MC is the best option, although most of it is partially or totally painted red. Ugly on a ceiling.

I can't see it, but a beam detector below may fit the bill better. It will depend on a bunch of factors

Since the inspector is treating each bay as a separate space: Wall mount the smokes in the bays (4"-12" from the ceilng). then only 180 degrees

We all know you (and I) would put the cable in first, in that case.

And use THHN/TFFN if you want (unless there's a local/customer/manufacturer regulation prohibiting it)

 

[kbsparky]

is this concrete ceiling what is rerferred to as a "waffle slab". it looks like a waffle only a lot bigger. i've always been under the impression that one smoke detector was required at the top af an elevator shaft. , but i digress, yes i don't see why you couldnt use greenfeild to accomplish the task at hand.it looks good per 620.21 in the NEC

Yeah, a really BIG waffle!!

Like I said earlier, there are already 2 smokes up there, but this guy decided that each hole could accumulate smoke, and therefore needed a detector ....

The center one has a rather large grate in it to ventilate air to the roof. That is where one of the smokes is right now, although it is hanging down a couple of feet from the top.

 

[gadfly56]

Yeah, a really BIG waffle!!

Like I said earlier, there are already 2 smokes up there, but this guy decided that each hole could accumulate smoke, and therefore needed a detector ....

The center one has a rather large grate in it to ventilate air to the roof. That is where one of the smokes is right now, although it is hanging down a couple of feet from the top.

If your jurisdiction follows NFPA-72, look at 5.7.3.2.4.2 (3) [2007 edition]; for "waffle or pan-type ceilings" if the beam depth is less than 24" and the spacing is less than 12 feet, you can use smooth ceiling spacing and put the detectors on the bottoms of the beams. Or take the customer's money, whichever.

 

[jewellfish]

waffle

waffle

If they follow NFPA 72 (2010) then 17.7.3.2.4.2 applies. If the beam depth is greater than .10 the ceiling height and beam spacing is less than .40 ceiling height, then normal spacing applies parallel to beams 1/2 spacing perpendicular.

 

[kbsparky]

is this concrete ceiling what is rerferred to as a "waffle slab". it looks like a waffle only a lot bigger. i've always been under the impression that one smoke detector was required at the top af an elevator shaft. , but i digress, yes i don't see why you couldnt use greenfeild to accomplish the task at hand.it looks good per 620.21 in the NEC

Looking at your response again, you mentioned elevator shaft. Is there a difference between the shaft and the equipment room as far as these requirements go? FWIW, the top of the shaft is a floor grate in the equipment room, which sometimes has a solid cover over it.