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#67735 07/13/06 10:08 PM
Joined: Dec 2004
Posts: 1,064
Need some info on when they are needed if you don't mind..

Reason, HVAC contractor adding new RTU's. Existing RTU's have Duct detectors installed.
Wouldn't these new ones need these and be tied into the fire system?


#67736 07/14/06 05:24 AM
Joined: Jul 2004
Posts: 129
Duct detectors are needed if the unit CFM rating is 2000 or greater on the return side.
If your unit is 4000 or greater you need them on supply and return. About the only thing they do is tell you that your duct has dust in it when the heat comes on.As far as early fire detection they are useless. Think about it you have a small fire in a room your HVAC is drawing clean air from other parts of the building when it gets back to the unit the air is so doluted there is no smoke to detect. But I know THE CODE REQUIRES THEM. I use to work for a fire alarn distributior we had Notifier and Pyrotronics equipment.

#67737 07/14/06 08:21 AM
Joined: Apr 2001
Posts: 507
I'm not that familiar with fire code so I can't say for sure what the code says.

We recently had a bid for a bank building, all smoke detection was removed because the building was sprinkled.

#67738 07/14/06 09:47 AM
Joined: Aug 2003
Posts: 64
The requirement comes from the mechanical code. In the IMC it is found in section 606. There are a couple of exceptions there that will often apply. There will be a simular section in the UMC.

#67739 07/14/06 10:28 AM
Joined: Mar 2002
Posts: 582
Ron Offline
Depending on the applicable mechanical code, most require connection the the building fire alarm system for monitoring (if there is a building fire alarm system).

#67740 07/14/06 01:10 PM
Joined: Apr 2002
Posts: 7,333
Likes: 7
From the Fire Sub-Code Insp (NJ)here, exactly as Hypress said. IF system within structure it must be interconnected to provide notification.

In instances of nuisance activation (dust/humidity/etc) PERMISSION can be granted for local alarm only.



#67741 07/14/06 07:26 PM
Joined: Mar 2005
Posts: 212
I would like to add that if the total CFM of all units in a discrete area (say a single tenant) is 2000 or more then the detectors are required. Not just the CFM of any one unit. They must be wired for unit shutdown and be monitored by the buildings central system. I'll quote NFPA when I find my book in this messy office.

#67742 07/14/06 07:37 PM
Joined: Dec 2004
Posts: 1,064
Single building, single tennant.

30,000 Sq/ft

Had 5 RTU's initially, 5 more added.

The orginal 5 have (DD), but the newer ones do not.

Typical fire system installed, building is sprinklered, and has been since the orginal build.

Are they not needed if sprinklered then?

#67743 07/14/06 08:20 PM
Joined: Jan 2003
Posts: 1,429
LK Offline
"Are they not needed if sprinklered then?"

Still need the detectors, the idea is to get notification, before the heat builds to trigger a sprinkler.

#67744 07/15/06 10:21 AM
Joined: Mar 2005
Posts: 212
Agree. Someone missed something somewhere.

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