• We will be performing upgrades on the forums and server over the weekend. The forums may be unavailable multiple times for up to an hour each. Thank you for your patience and understanding as we work to make the forums even better.

Combo Fire/Smoke Damper 24 VAC Power Supply

Status
Not open for further replies.
S

Sean.Day72

Member
Location
Florida
I have (5) combo smoke/fire dampers in 2 hours rated walls in a new facility. The are constantly fed 24VAC through a normally closed contact on the Fire Alarm and a fused link, if either pops open the dampers springs shut.

My question is there any special power supply that is required to power the 24VAC actuators in the dampers since this is part of a fire/smoke protection system? I was looking at the Functional Device Inc. Model PSH500A-LVC . Converts (1) 120VAC input into (5) 24VAC outputs. If not, can someone recommend one that meets any required code?

The actuators are only used to open the dampers back up after a smoke alarm or fire to "reset" them to their normally open position. They also will test their function once a year for annual maintenance.

Thanks!
 
tortuga

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Its been a while since i did these,
If its 'controlled' by the fire alarm system then your into Article 760 and probably need to look into 760.121 and a Class 3 or PLFA power supply.
I would check with the manufacturer of the dampers and see how much each one draws and size a 24V transformer based on that.
That PSH500A-LVC looks to be a class 2 device.
Perhaps others will chime in.
 
gadfly56

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
It may depend on how your AHJ views things (may require listing to UL-1481), but the power supply should get the job done. Is power applied to open the dampers with spring or other stored energy return? If so, then you have a class "D" fail safe circuit and almost anything should be suitable.

One thing to watch for, and not your responsibility, are fan shut downs so you don't turn rectangular duct into round duct, or blow a joint.
 
S

Sean.Day72

Member
Location
Florida
It is a "fail safe"operation. If the power supply fails or is destroyed the vent springs shut. Basically if 24V is lost through a normally closed contact it closes.

Power is only to reopen after an alarm or test the louver, its similar to a door holder set up.

I directed the contractor to provide a 100VA, 120VAC/24VAC transformer with fusible output. Actuators are only 10VA each.
 
Status
Not open for further replies.
Top