Carrier 50KC04-06 Service And Maintenance Instructions

20Fig. 24 — Smoke Detector SensorAir is introduced to the duct smoke detector sensor’s sensingchamber through a sampling tube that extends into the HVACduct and is directed back into the ventilation system through a(shorter) exhaust tube. The difference in air pressure betweenthe two tubes pulls the sampled air through the sensing cham-ber. When a sufficient amount of smoke is detected in the sens-ing chamber, the sensor signals an alarm state and the control-ler automatically takes the appropriate action to shut down fansand blowers, change over air handling systems, notify the firealarm control panel, etc.The sensor uses a process called differential sensing to preventgradual environmental changes from triggering false alarms. Arapid change in environmental conditions, such as smoke froma fire, causes the sensor to signal an alarm state but dust anddebris accumulated over time does not.For installations using two sensors, the duct smoke detectordoes not differentiate which sensor signals an alarm or troublecondition.Smoke Detector LocationsSUPPLY AIRThe Supply Air smoke detector sensor is located to the left ofthe unit’s indoor (supply) fan. See Fig. 25. Access is throughthe fan access panel. There is no sampling tube used at this lo-cation. The sampling tube inlet extends through the side plateof the fan housing (into a high pressure area). The controller islocated on a bracket to the right of the return filter, accessedthrough the lift-off filter panel.Fig. 25 — Typical Supply Air Smoke DetectorSensor LocationRETURN AIR WITHOUT ECONOMIZERThe sampling tube is located across the return air opening onthe unit basepan. See Fig. 26. The holes in the sampling tubeface downward, into the return air stream. The sampling tube isconnected via tubing to the return air sensor that is mounted ona bracket high on the partition between return filter and con-troller location. (This sensor is shipped in a flat-mounting loca-tion. Installation requires that this sensor be relocated to its op-erating location and the tubing to the sampling tube be con-nected. See installation steps below.)Fig. 26 — Typical Return Air Detector LocationRETURN AIR WITH ECONOMIZERThe sampling tube is inserted through the side plates of theeconomizer housing, placing it across the return air opening onthe unit basepan. See Fig. 27. The holes in the sampling tubeface downward, into the return air stream. The sampling tube isconnected via tubing to the return air sensor that is mounted ona bracket high on the partition between return filter and con-troller location. (This sensor is shipped in a flat-mounting loca-tion. Installation requires that this sensor be relocated to its op-erating location and the tubing to the sampling tube be con-nected. See installation steps below.)SEE DETAIL ADETAIL APLUGSAMPLING TUBE(ORDERED SEPARATELY)COUPLINGMAGNETICTEST/RESETSWITCHALARMTROUBLEPOWERDIRTYSENSORCOVERCOVER GASKET(ORDERING OPTION)SENSOR HOUSINGAND ELECTRONICSEXHAUST GASKETEXHAUST TUBE DUCT SMOKE SENSORINTAKEGASKETTSD-CO2(ORDERING OPTION)SUPPLY AIRSMOKE DETECTOR*RA detector must be moved from shippingposition to operating position by installer.RETURN AIR DETECTORSAMPLING TUBERETURN AIRDETECTOR MODULE(Shipping positionshown)*CONTROLLERMODULE