smoke detectors in air ducts and water condensation
smoke detectors in air ducts and water condensation
(OP)
Hi, I'm thinking of installing smoke detectors into air conditioning ducts and I am wondering if I'm going to have problems with water condensation getting into the smoke detectors and killing them.
Anyone have any experience in this area and could tell me if there is going to be a lot of water condensation? If there is then any ideas on stopping it getting into the smoke detectors?
Thanks.
Anyone have any experience in this area and could tell me if there is going to be a lot of water condensation? If there is then any ideas on stopping it getting into the smoke detectors?
Thanks.





RE: smoke detectors in air ducts and water condensation
Generally smoke detectors are installed in return ducting and are used to control fire control dampers. We have been using them for years and I am not clear about your possible doubt of condensation. Why do you anticipate it?
Regards,
Repetition is the foundation of technology
RE: smoke detectors in air ducts and water condensation
RE: smoke detectors in air ducts and water condensation
RE: smoke detectors in air ducts and water condensation
In most of the installations I see, the detector housing uses pitot tube technology in that total (velocity plus static) pressure enters ports in a tube protruding into the air stream, facing the moving air. Static pressure is sensed by a simple tube from the detector housing into the duct. Basically, the difference between the total pressure and static pressure (equal to velocity pressure - preferably 400 feet per minute or greater) drives flow through the smoke detector, which is mounted within a chamber that experiences flow-through by this differential sensed by the tubing protruding into the duct.
Condensation will only occur if the surface temperature within the tubing is below the dewpoint of the air in the duct. Since this is a continually flowing system, the smoke detector sensing tubing attains equilibrium temperature with the duct air temperature. This means that if air doesn't condense randomly within the duct, it will also not condense on the wall of the smoke detector sensor tubing.
Basically, no worries, as long as the sensing location is away from water sources such as humidifiers.
Personally, in my experience, I have never seen problems with condensate adversely affecting in-duct smokes.
RE: smoke detectors in air ducts and water condensation
The result was "raining" in the ductwork, which caused all kinds of raining below the ductwork, and the smoke detector was activated. This was an abnormal condition and the only occurence I have ever witnessed in my career.
Generally speaking, this should not be a problem if your smoke detector is located an appropriate distance downstream of your humidifier (if you have one in the duct) and if your high humidity limit is properly set.
RE: smoke detectors in air ducts and water condensation
RE: smoke detectors in air ducts and water condensation
For Eyeap's purposes, I would not worry about condensation in a detector that will be at equilibrium with the duct air temperature.
RE: smoke detectors in air ducts and water condensation