Carrier 50TCQD14 Installation Instructions Manual

Also see for 50TCQD: Installation instructions

Contents

22For wire runs up to 50 ft. (15 m), use no. 18 AWG(American Wire Gage) insulated wire (35_C minimum).For 50 to 75 ft. (15 to 23 m), use no. 16 AWG insulatedwire (35_C minimum). For over 75 ft. (23 m), use no. 14AWG insulated wire (35_C minimum). All wire sizeslarger than no. 18 AWG cannot be directly connected tothe thermostat and will require a junction box and spliceat the thermostat.XCGW2CW2GW1O/B/Y2 Y2RW1RY1 Y1THERMOSTAT(Note 1)(Note 2)Note 1: Typical multi-function marking. Follow manufacturer’s configurationinstructions to select Y2. Do not configure for O output.Note 2: W2 connection not required on units without electric heating.Field WiringCentralTerminalBoardTypicalThermostatConnectionsC09012Fig. 34 -- Typical Low--Voltage Control ConnectionsCentral Terminal BoardThe Central Terminal Board (CTB) is a pass throughconnection point. The CTB provides the capability to addfactory--installed options and field--installed accessories tothe units by cutting jumper wires without having to changeor reroute wires through the structure of the unit. The CTBdoes not provide any microprocessor control; it is simply abasic multifunction wiring terminal configuration.Commercial Defrost ControlThe Commercial Defrost Control Board (DFB)coordinates thermostat demands for supply fan control, 1or 2 stage cooling, 2 stage heating, emergency heating anddefrost control with unit operating sequences. The DFBalso provides an indoor fan off delay feature (userselectable). See Fig. 35 for board arrangement.DIPSwitchesSpeed-UpJumpersC09275Fig. 35 -- Defrost Control Board ArrangementThe DFB is located in the 50TCQ unit’s main control box(see Fig. 36 on page 23). All connections are factory--madethrough harnesses to the unit’s CTB, to IFC (belt--drivemotor) or to ECM (direct--drive motor), reversing valvesolenoids and to defrost thermostats. Refer to Table 5 fordetails of DFB Inputs and Outputs.Reversing valve control — The DFB has two outputs forunit reversing valve control. Operation of the reversingvalves is based on internal logic; this application does notuse an “O” or “B” signal to determine reversing valveposition. Reversing valves are energized during thecooling stages and the defrost cycle and de--energizedduring heating cycles. Once energized at the start of acooling stage, the reversing valve will remain energizeduntil the next heating cycle demand is received. Oncede--energized at the start of a Heating cycle, the reversingvalves will remain de--energized until the next coolingstage is initiated.Compressor control — The DFB receives inputs indicatingStage 1 Cooling, Stage 2 Cooling and Stage 1 Heating fromthe space thermostat or unit control system (PremierLinktcontroller or RTU Open controller); it generates commandsto start compressors with or without reversing valveoperation to produce Stage 1 Cooling (one compressor runs),Stage 2 Cooling (both compressors run) or Stage 1 Heating(both compressors run).Auxiliary (Electric) Heat control — The 50TCQ unit canbe equipped with one or two auxiliary electric heaters, toprovide a second stage of heating. The DFB will energizethis Heating System for a Stage 2 Heating Command(heaters operate concurrently with compressor(s) in the Stage1 Heating cycle), for an Emergency Heating sequence(compressors are off and only the electric heaters areenergized) and also during the Defrost cycle (to eliminate a“cold blow” condition in the space).