duct detector/ fresh air question

[cda]

Church has two separate a/c units

OVER 2000 cfm,

and cannot meet the exception:::

Exception: Smoke detectors shall not be required where air distribution systems are incapable of spreading smoke beyond the enclosing walls, floors and ceilings of the room or space in which the smoke is generated.

1. fresh air intake is about two feet from the duct detector

2. duct detector cannot be moved already at the return and short vent return.

3. no area smoke detectors

I am thinking the duct detector is getting dirt, cold air, moisture, which sets the duct detector into alarm.

any suggestions??

 

[fireguy]

We have seen where the intake duct detector is upstream of a filter. After moving the detector downstream of the filter, the problems of dirty, wet detectors going into false alarm decrease or stop. Unless the detector has been damaged by the moisture and dirt. Then the detector needs to be changed, preferably at not cost to the customer.

I am not sure what the lowest temp rating is on detectors. http://www.systemsensor.com/en-us/Pages/2251BR.aspx This detector is listed for 32°F. Others may be different. Each smoke is packaged with a spec sheet that lists that information.

http://www.systemsensor.com/en-us/Documents/DuctApplicationSmokeDetectors_AppGuide_A05-1004.pdf

 

[cda]

We have seen where the intake duct detector is upstream of a filter. After moving the detector downstream of the filter, the problems of dirty, wet detectors going into false alarm decrease or stop. Unless the detector has been damaged by the moisture and dirt. Then the detector needs to be changed, preferably at not cost to the customer. I am not sure what the lowest temp rating is on detectors. http://www.systemsensor.com/en-us/Pages/2251BR.aspx This detector is listed for 32°F. Others may be different. Each smoke is packaged with a spec sheet that lists that information.

http://www.systemsensor.com/en-us/Documents/DuctApplicationSmokeDetectors_AppGuide_A05-1004.pdf

I thought the duct detector is required to be before the filter??? I need to look at 72 tomorrow

 

[mtlogcabin]

606.2.1 Return air systems.

Smoke detectors shall be installed in return air systems with a design capacity greater than 2,000 cfm (0.9 m3/s), in the return air duct or plenum upstream of any filters, exhaust air connections, outdoor air connections, or decontamination equipment and appliances.