Carrier 48MPD Installation, Start-up And Service Instructions Manual

Contents

Hot Gas Bypass — An optional hot gas bypass systemmay be factory installed on circuit no. 1. This system willintroduce discharge vapor from the compressor discharge lineinto the distributors and evaporator coil circuits on circuitno. 1 when suction pressures drop to damaging levels. Nofield adjustments of the hot gas bypass valve should berequired.Condenser Fans — Each fan is supported by a formedwire mount bolted to fan deck and covered with a wire guard.The exposed end of the fan motor shaft is protected fromweather by grease. If fan motor must be removed for serviceor replacement, be sure to regrease fan shaft and reinstallfan guard. For proper performance, fan should be 7 ⁄8 in.(22 mm) below top of venturi on the fan deck to top ofthe fan hub. (See Fig. 64.) Tighten set screws to 15 ± 1 ft-lbs(20 ± 1.3 N-m). Figure 64 shows proper position ofmounted fan.IMPORTANT: Check for proper fan rotation (clock-wise viewed from above). If necessary to reverse, switchleads.Compressor Removal — Access to the pump end ofthe compressor is from the compressor side of the unit.Access to the motor end of the compressor is from the insideof the unit. All compressors can be removed from the com-pressor side of the unit.IMPORTANT: All compressor mounting hardware andsupport brackets removed during servicing must be re-installed prior to start-up.1. Disconnect power to unit; lockout power to compressor.2. Close suction and discharge service valves.3. Relieve refrigerant pressure into a refrigerant recoverysystem.4. Remove:a. Fan-cycling pressure switch (FCPS)b. High-pressure switchc. Low-pressure switch5. Disconnect power wires at terminal box and disconnectconduit.6. Disconnect wires from crankcase heater.7. Disconnect service valves from compressor.NOTE: On units with 2 compressors per circuit, discon-nect both oil equalizer lines located on the motor barreland on the oil pump sump.8. Units 48/50MP62L:a. Remove 4 large screws securing compressor mount-ing pan to unit base rail.b. Slide compressor (on mounting pan) to outside of unitframe; support and/or lower to ground.c. Unbolt compressor from mounting pan and remove.9. Units 48/50MP70M,82N,90P,10R:a. Remove 4 large screws securing compressor to the com-pressor rails.b. Lift compressor off mounting bolts and remove.Compressor Replacement — Perform the following:1. Reverse procedure in Compressor Removal section to endof Step 4.2. Reinstall service valves and safety switches, and tightento torques as listed:TORQUE COMPRESSOR(S)Tighten discharge valves to —20-25 ft-lbs ( 27- 34 N-m) 06E-25080-90 ft-lbs (109-122 N-m) 06E-265,275,299Tighten suction valves to —80- 90 ft-lbs (109-122 N-m) 06E-25090-120 ft-lbs (122-163 N-m) 06E-265,275,299Tighten the following fittings as specified —120 in.-lbs (13.5 N-m) High-Pressure Switch120 in.-lbs (13.5 N-m) Low-Pressure Switch3. Leak-check and evacuate system, reclaim refrigerant.4. Recharge system per pre-start-up and start-up sequences.Recheck oil levels.5. Energize crankcase heater for 24 hours prior to restart ofsystem.TROUBLESHOOTINGThe 48/50MP units provide extensive troubleshooting in-formation to service personnel through the use of status codesand alarm and alert codes from the control system, whichare displayed on the unit HSIO or through the use of ServiceTool or CCN Building Supervisor. For more information ondiagnostics, codes, and possible causes, refer to the Controlsand Troubleshooting manual.Use the Quick Test function to check control inputs andoutputs (including economizer actuators). Refer to Controlsand Troubleshooting Guide.If there are indications of hunting (rapid oscillations) ofcontrol functions (such as duct static pressure or supply airtemperature), or if the response rate is too slow, check thegain values. Refer to the Control Loop Checkout section onpage 40 for more information.If the unit is equipped with an optional VFD and the sup-ply or exhaust fan is not running when required, refer to thetroubleshooting section of the separate VFD technical manualprovided with the unit.For troubleshooting information on mechanical systems,refer to the troubleshooting and diagnostics table on the nextpage.NOTE: Fan rotation is clockwise when viewed from top of unit.Fig. 64 — Condenser Fan Adjustment55