Fire alarm / mechanical code question

[nscherneck]

I'm bidding a fire alarm tenant improvement project in a five story building (non high-rise). There are VAVs with CFM ratings exceeding 2000. My question is do these VAVs require a duct detector or do the existing duct detectors in the main supply duct satisfy the code (IMC 609)?

 

[Jesse7623]

I would think that it may.But the best way to know is to ask the AHJ.
Local municipalities are always a little different.

 

[nhfire77]

OK, I have no idea what a VAV is.

 

[ronmath]

What you are referring to is either a Fan Powered VAV or Fan coil unit and my experience is that a duct smoke detector would be required if over 2000 CFM. You could also use area smoke detectors for each room served by the units. This might be less expensive in some situations. I agree about talking with the AHJ ahead of time.

 

[barbeer]

my experience is that a duct smoke detector would be required if over 2000 CFM.

I agree about talking with the AHJ ahead of time.

I concur.

Definitely review the building/mechanical codes for wherever you are/talk to AHJ.

 

[STHOMAS]

The mechanical code dictates air moving "systems" over 2000 cfrm require automatic shut down. This also includes two or more units each under 2000 cfm serving the same area and totaling over 2000 cfm would require detection on each unit and global shutdown.

I believe you are going to need a duct detector on each VAV if it is over 2K cfm, as well as multiple units each under 2k if they serve the same area and total over 2k.

Check the exceptions in the mechanical code, you may find one that applies. The reason is simply to help minimize the number of duct detectors installed for the simple reason that DD's are prone to false alarms.

Anyway, check out this application guide from System Sensor...info may help.

http://www.systemsensor.com/pdf/A05-1004.pdf

 

[Stallzer]

A VAV = Variable air volume box, and no it does not require a Duct Detector. Duct Detectors are usually used as a control device and are not considered Life Safety devices.
Since you can't shut down a RTU / AHU via a VAV, it's not required. Most 5 story building would contain hundreds of VAV's, and it would be quite the bill for that many Duct Detectors.For further reference check NFPA 90A & 90B.

 

[RJohnsonMasterElectrician]

5.16.4.2.2.2

 

[nakulak]

in my area all we ever had to do was install one duct smoke and shunt the unit to off. the duct detectors here go in the return so supply side vavs don't have anything to do with it (do you actully have vavs on the return ? - never seen that) the only problem we have is generally placement of an indicator - inspectors often require a remote visual/audible indicator.

 

[RJohnsonMasterElectrician]

also, if the state requires HRV?or if they are just put in (heat, vent recovery systems), if that is over the 2000cfm max that also must be shut down along with the ac,heat units