Carrier Weathermaster 48HJD Series Product Data

Also see for 48HJD005: Installation, Start-Up and Service Instructions

58Heating, units with economizer/two-positiondamper — When the thermostat calls for heating, termi-nal W1 is energized. The induced-draft motor is energizedand the burner ignition sequence begins. The indoor (evap-orator) fan motor (IFM) is energized 45 seconds after aflame is ignited and the damper moves to the minimum po-sition. If the accessory two-position damper is used, theoutdoor-air damper opens to the minimum position when-ever the evaporator fan runs. On units equipped for twostages of heat, when additional heat is needed, W2 is ener-gized and the high-fire solenoid on the main gas valve(MGV) is energized. When the thermostat is satisfied andW1 is deenergized, the IFM stops after a 45-second time-off delay. The economizer damper then moves to the fullyclosed position. When using continuous fan, the damperwill remain in the minimum position.Operating sequence for 48HJ008-014 unitsCooling, units without economizer — When thermo-stat calls for cooling, terminals G and Y1 are energized.The indoor (evaporator) fan contactor (IFC) and compres-sor contactor no. 1 (C1) are energized, and evaporator-fanmotor, compressor no. 1, and condenser fans start. Thecondenser-fan motors run continuously while unit is cool-ing. For units with 2 stages of cooling, if the thermostatcalls for a second stage of cooling by energizing Y2, com-pressor contactor no. 2 (C2) is energized and compressorno. 2 starts.When the thermostat is satisfied, C1 and C2 are deener-gized and the compressors and outdoor (condenser) fanmotors (OFM) shut off. After a 30-second delay, the indoor(evaporator) fan motor (IFM) shuts off. If the thermostat fanselector switch is in the ON position, the evaporator mo-tors will run continuously.Cooling, units with Durablade economizer — Whenthe outdoor-air temperature is above the OAT setting andthe room thermostat calls for cooling, the compressor con-tactor no. 1 is energized to start compressor no. 1 and out-door (condenser) fan motors (OFM). The indoor (evapora-tor) fan motor (IFM) is energized and the economizerdamper moves to the minimum position. Upon a furthercall for cooling, compressor contactor no. 2 will be ener-gized, starting compressor no. 2. After the thermostat issatisfied and the IFM is deenergized, the damper moves tothe fully closed position.When the outdoor-air temperature is below the OAT set-ting and the thermostat calls for Y1 and G, the economizerdamper moves to the minimum position when the evapo-rator fan starts. The first stage of cooling is provided by theeconomizer. If the supply-air temperature is above 57 F, aswitch on the supply-air thermostat is closed between theT2 terminal and the 24 vac terminal. This causes thedamper to continue to modulate open until the supply-airtemperature falls below 55 F or the damper reaches thefully open position.When the supply-air temperature is between 55 F and52 F, the supply-air thermostat has open switches betweenthe T2 and 24 vac terminals and between the T1 and24 vac terminals. This causes the economizer damper toremain in an intermediate open position.If the supply-air temperature falls below 52 F, a switchon the supply-air thermostat is closed between the T1 ter-minal and the 24 vac terminal. This causes the damper tomodulate closed until the supply-air temperature risesabove 55 F or the damper reaches the minimum position.When the supply-air temperature is between 55 F and57 F, the supply-air thermostat has open switches betweenthe T2 and 24 vac terminals. This causes the economizerdamper to remain in an intermediate open position.If the outdoor air alone cannot satisfy the cooling re-quirements of the conditioned space, economizer coolingis integrated with mechanical cooling, providing secondstage cooling. Compressor no. 1 and condenser fan will beenergized, and the position of the economizer damper willbe determined by the supply-air temperature. Compressorno. 2 is locked out.When the second stage of cooling is satisfied, the com-pressor and condenser fan motors will be deenergized.The damper position will be determined by the supply-airtemperature.When the first stage of cooling is satisfied, the IFM shutsoff after a 30-second delay. The damper then moves to ful-ly closed position.Cooling, units with EconoMi$erWhen the outdoor-air temperature (OAT) is above theECON SP set point and the room thermostat calls forStage 1 cooling (R to G + Y1), the indoor (evaporator) fanmotor (IFM) is energized and the EconoMi$er dampermodulates to minimum position. The compressor contac-tor is energized to start the compressor and outdoor (con-denser) fan motor (OFM). After the thermostat is satisfied,the damper modulates to the fully closed position when theIFM is deenergized.When the OAT is below the ECON SP setting and theroom thermostat calls for Stage 1 cooling (R to G + Y1),the EconoMi$er modulates to the minimum position whenthe IFM is energized. The EconoMi$er provides Stage 1 ofcooling by modulating the return and outdoor-air dampersto maintain a 55 F supply air set point. If the supply-airtemperature (SAT) is greater than 57 F, the EconoMi$ermodulates open, allowing a greater amount of outdoor airto enter the unit. If the SAT drops below 53 F, the outdoorair damper modulates closed to reduce the amount of out-door air. When the SAT is between 53 and 57 F, theEconoMi$er maintains its position.If outdoor-air alone cannot satisfy the cooling require-ments of the conditioned space, and the OAT is above theMECH CLG LOCKOUT set point, the EconoMi$er inte-grates free cooling with mechanical cooling. This is accom-plished by the strategies below.NOTE: Compressor has a two minute Minimum On, Mini-mum Off, and Interstage delay timer.1. If Y1 is energized, and the room thermostat calls forY2 (2-stage thermostat), compressor no. 1 and OFMare energized. The position of the EconoMi$erdamper is maintained at its current value.2. If Y1 is energized for more than 20 minutes, and Y2is not energized (whether or not a 2-stage thermostatis used), compressor no. 1 and OFM are energized.Controls (cont)