Duct Mounted Smoke Detectors

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You don't mount it.

Generally I turn the detectors over to the Mech Contractor for mounting so there is no way I could accidentally put a hole in something like a coil or refrigeration line.
 
Even if there is a plenum at some point there is usually a small piece of duct attached near the unit, and that is the only place I have seen plenum detectors mounted. (just what I have seen for what its worth)
 
If there is a huge opening to the plenum, I've had spot type detectors installed on 24" centers like a checker board across the opening. I've also mounted duct detectors on angle on one side of the plenum so that the sampling tube runs across the large opening (24" apart).
 
We dont mount them

On a side not what kind of unit cost do you guys use on one of these?

there seems to be a fair amount of labor in wiring them with the low voltage interconnections etc etc
It seems like an easy item to underestimate

Jim
 
jimmyglen said:
We dont mount them

On a side not what kind of unit cost do you guys use on one of these?

there seems to be a fair amount of labor in wiring them with the low voltage interconnections etc etc
It seems like an easy item to underestimate

Jim
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They are very easy to underestimate as I have learned from the school of hard knocks. There are a ton of variables you usually dont have an answer to until you get on the job. Here is a list of variables I can think of. I am sure there are more.

1) Who supplies the duct detectors. EC, MC or FA contractor

2) Who installs the detector.

3) Who does the control wiring to the RTU

4) How high off the ground will they be located

5) Do you need detectors on both supply and return sides.

6) Is a remote test switch required and where will it be located

7) Is the supply 120 or 24 volt

8) Does the detector need to be monitored by the FACP

9) Do the detectors need to be reset from the FACP

10) Is the detector addressable or do I need a monitor module

The prints and specs usually don't answer these questions. Sometimes you can get answers from the fire dept. or mechanical contractor. If the job requires just a couple detectors I usually put in about 3 hours each. I also exclude suppling the detector unless something specifcally tells me to supply it.
 
Where do you mount the detector when you have a plenum return"

Guess I was spoiled. By spec, we always had detailed drawings generated by our FA sub that showed exactly where to mount every device, including those pesky duct detectors. Our subs design was mandated by, and followed, the NFPA.

We just piped, wired, tested the wire, mounted devices, supported the testing, and eventually, and eventually, and eventually went home!!!

This was US government work. In the last 15 years there was only one FA sub available to ECs. All ECs had to use him, and he was a PITA!
Rhetorical question: do you think he was competitive?

Not much help to you here.

Best Wishes Everyone in 2008
 
12- who programs the device?

The sample tube extends at least 1/2 the width of the duct (usualy the whole width,with a plug on the end). and should (must) be 6' from a bend.

It should be a photo and not on alarm verification. supervisory is ok (non alarm).
 
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