Duct Smoke Detectors RTS RTU
When your duct detectors are tied into your fire alarm system there are a few things to remember.
Duct Smoke Detectors consist of the following: A housing many times with built in relays to shut down the air handler, a smoke detector inside the housing, tubes that allow air to be sampled and then send the air back on it's way. The size of these tubes vary. Sometimes you have a monitor module with the set up on the addressable systems or you may have just a zoned wire tie in. Sometimes there is a remote test switch to allow testing and reset from a remote location.
Duct Detectors may be 120 V, 240 V or 24 VDC or 24VAC
1. If the air handlers are over 2000 cfm the duct detectors should be tied to the fire alarm system.
2. When the air handler is over 15,000 cfm you should have duct detectors both on supply and return.
3. Many fire marshals will allow you to have the duct detectors notify the central station as a supervisory signal instead of a full blown alarm that dispatches the fire trucks. Verify this at time of installation.
4. When the duct detectors are not readily accessible and not on an addressable system many times RTS Remote Test Switches will be required in the area below the duct detector so you can do a test and a reset without going to the unit.
5. Global Shut down is when one unit receives a smoke alarm and then reports to the fire alarm panel and the fire alarm panel sends a signal through relays to shut down all the air handler units not just the one that went into alarm.
6. Most of the time it is not global but individual so when smoke is detected in the duct work then that duct detector shuts down that air handler. If a belt is burning or if the motor is burning this helps protect the equipment. Shutting down the air handler does not allow the spread of smoke throughout the building.