The duct smoke detector is equipped with an auxiliary relay.
Hvac duct smoke detector requirements.
The automatic shutoff shall interrupt the power to the air moving system by the use of a smoke detector located in the main supply air duct.
The ashrae handbook of smoke control engineering nfpa life safety book for health.
Summary duct smoke detector requirement air moving systems supplying air in excess of 2 000 cfm to enclosed spaces within buildings shall be equipped with an automatic shutoff.
Duct smoke detection nfpa 90a code requirements there are exceptions to the two basic requirements.
A duct smoke detector should shut off a typical blower and fresh air and turn on the exhaust duct detectors aren t a replacement for room sensors if the duct system is designed to carry more than 2000 cfm 5 tons nominal of air you need one in the return if imc is being followed and the supply if nfpa is being followed.
Nfpa 72 also states that a duct smoke detector is not allowed to replace an area smoke detector mainly because if the air handling unit ahu is not running the detector would not detect smoke.
Therefore duct smoke detectors are typically considered mechanical equipment devices instead of life safety devices.
A heating ventilating or air conditioning hvac fan motor overheats and resulting smoke is sensed by the duct smoke detector installed in the main supply duct.
Duct smoke detection may be useful in preventing injury and property dam age in instances such as the following.