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#37648 05/01/04 03:08 PM
Joined: Feb 2004
Posts: 17
S
Member
I have a question about the wiring of fire damper motors used to cut off movement of air between rooms and hallways in case of fire.

How do they interact with fire alarm cable. I assume the power feed is probably #12 wire or mc cable to a switch located near the damper and then the switch leg goes to feed the little motor.

But where does this power come from and how does it communicate with the fire alarm control panel? -thanks

#37649 05/01/04 04:53 PM
Joined: Dec 2003
Posts: 20
T
Member
Fire Dampers usually run on 120V dedicated circuits.

Typically there is a heat or smoke detector on one or both sides of the fire wall mounted on a relay base or with internal relays.

Most of the dampers I've installed require power to close but have a fusible link usually around 185F in case the power is out.

The detectors are wired into the Fire Alarm Panel plus they have the additional contacts for the damper to operate. If one of these detectors goes into alarm the damper will close and the FA panel go into alarm unless you are in an older building with dampers but no Fire Alarm.


Mark Stetson
Stetson Electric
#37650 05/01/04 11:08 PM
Joined: Jun 2003
Posts: 1,143
D
Member
They can be shut by system activation, or zone activation. Zone activation is what you're describing - the system in the rest of the building stays in "normal" mode, but if there's a detector off on the 2nd floor, then the 2nd floor HVAC gets isolated.
General activation (not sure if that's the "proper" term) shuts down the HVAC in case the fire alarm goes off, and doesn't turn back on until the system resets, or FD activates it (see below).

We've also seen them tied into duct detectors - smoke in the duct shuts down the system, and the dampers. When the FD resets, system goes back to normal. Usually the duct dectector is wired to an LED on the outside of the duct, or in the adjoining passageway, to assist in locating the detector.

Fancier systems also have an "FD" override, for evacuation of nuisance smoke - basically, it's a preset where the fans will turn on, and certain dampers will open to exhaust fumes / smopke from an area, but only if the FD / building security activates that aspect of the system.

#37651 05/02/04 03:13 PM
Joined: Mar 2004
Posts: 11
K
Member
the FSD's that Ive seen open on power and close on loss of power. Due to the wound up spring. close upon power loss seems to make more sence. If heat or fire was to trip breakers or damage a cable before the fsd closed.

#37652 05/03/04 11:27 PM
Joined: Feb 2001
Posts: 32
G
Member
I have always put them on the door holder circuit on many buildings in Seattle.

#37653 05/06/04 10:02 AM
Joined: May 2003
Posts: 8
B
Junior Member
does your building have a smoke evacuation system? If so, Relay bases on local detectors may not be enough.

If you have a generator I would use a 120V equipment branch circuit.

I have never used a Smoke damper that required power to close. I have seen units that close whenever power is droped. If it is a Fire/Smoke damper it will have a fusible link that will drop the damper. I have always used a Macabe link. This will drop the damper 'independantly' of the fire alarm system. The ones I have used mechanically break the linkage from the motor. Because the ones I use Spring closed(not powered closed) the damper snaps shut, regardless if the fire alarm wiring is intact, or if power is on.

#37654 05/06/04 11:48 AM
Joined: Oct 2003
Posts: 172
G
Member
you can use a double voltage relay in order to accomplish this as well.


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