Carrier 50JZ Product Data

Also see for 50JZ 024-060: Installation and operating instructions Guide to operating and maintaining Guide to operating and maintaining Product data Installation, Start-Up and Service Instructions

Contents

28Sequence of operationWhen power is supplied to unit, the transformer (TRAN) isenergized.On units with crankcase heater, heater is also energized.Cooling — With the thermostat subbase in the coolingposition, the thermostat makes circuit R-O. This energizesthe reversing valve solenoid (RVS) and places the unit instandby condition for cooling.As the space temperature rises, the thermostat makes,closing circuit R-Y. A circuit is made to contactor (C),starting the compressor (COMP) and outdoor-fan motor(OFM). Circuit R-G is made at the same time, energizing theindoor-fan relay (IFR) and starting the indoor-fan motor(IFM) after a 1-second delay†.When the thermostat is satisfied, contacts open, deenergizingC. The COMP and OFM stop, and the IFM stops after a 60sec time delay†.Heating — On a call for heat, thermostat makes circuits R-Y and R-G.A circuit is made to C, starting COMP and OFM. Circuit R-G also is completed, energizing IFR and starting IFM after a1-sec delay†.Should room temperature continue to fall, circuit R-W ismade through second-stage thermostat bulb. If optionalelectric heat package is used, a relay is energized, bringingon first bank of supplemental electric heat. When thermostatis satisfied, contacts open, deenergizing contactor and relay;motors and heaters deenergize. The IFM is controlled by atime-delay relay that keeps the fan on for 60 sec†.Defrost — Defrost board (DB) is a time and temperaturecontrol, which includes a field-selectable time period (Dipswitch 1 and 2 on the board) between checks for defrost (30,60, 90, or 120 minutes). Electronic timer and defrost cyclestart only when contactor is energized and defrost thermostat(DFT) is closed.The defrost board is also equipped with a 3rd dip switch forselecting Quiet Shift operation. The Quiet Shift operationturns compressor off at defrost initiation and termination.Unit is factory shipped with quiet shift turned off.Defrost mode is identical to cooling mode, except outdoorfan motor stops and a bank of optional electric heat turns onto warm air supplying the conditioned space.NOTES:1.† Standard PSC indoor motor.2. Compressor time delay occurs through the defrost controlboard.3. Defrost control board has built in 5 minute compressordelay: once the compressor has started and then stopped, itcannot be restarted again until 5 minutes have elapsed.4. ICM FIOP models only—The indoor blower operationwith a call for fan operation (G) in either cooling or heatpump heating (compressor) modes will perform by the on/off delay profile selected at start up on the easy select™board.Controls