Carrier Omnizone 50XCR06 Installation, Start-up And Service Instructions Manual

Contents

18Compressor Rotation — To determine whether or notcompressor is rotating in the proper direction:1. Connect service gages to suction and discharge pressurefittings.2. Energize the compressor.3. The suction pressure should drop and the discharge pres-sure should rise, as is normal on any start-up.4. If the suction pressure does not drop and the dischargepressure does not rise to normal levels, the compressormay be rotating in the wrong direction.5. Since the compressor and fan motors are connected inphase during production, it is likely that the evaporatorand condenser fans are probably also rotating in thewrong direction.6. Turn off power to the unit, lock and tag disconnect perstandard safety procedures.7. Reverse any two of the unit power leads.8. Remove lock and tag per standard safety procedures andreapply power to the unit.9. The suction and discharge pressure levels should nowmove to their normal start-up levels.NOTE: When the compressor is rotating in the wrong direc-tion, the unit makes an elevated level of noise and does notprovide cooling.Operating Sequence — All units require the additionof a thermostat accessory package to complete the control cir-cuit. The sequence of operation may vary depending on whichpackage is selected.ROOM-MOUNTED THERMOSTAT — These units use anelectronic thermostat mounted in the conditioned space.FAN CIRCULATION — The indoor-fan motor is energizedthrough G on the thermostat and the indoor-fan contactor isenergized. This starts the indoor-fan motor (IFM). The fan willoperate to provide continuous air circulation.COOLING — The indoor fan will operate continuously orwhen the compressor runs, depending on the setting of the ther-mostat fan selector switch. When the thermostat closes (on acall for cooling Y1 on the thermostat), the control relay (CR),outdoor-fan contactor (OFC) and compressor contactor(s) (C1and C2 on 50XCR12-16 units) close. The control relay willstart the indoor fan if it is not already running. The compressorcontactors will immediately start the first stage compressor(s).A second stage on 50XCR12-16 units will close if addition-al cooling demand is required, and will then start the second-stage compressor. When the thermostat is satisfied, the secondstage compressor will stop first, and then the first stage com-pressors will stop when cooling demand is satisfied.ALL UNITS — The control circuit incorporates a currentsensing lockout relay (Cycle-LOC™ device) that locks off thecompressor(s) for 5 minutes when any safety device is activat-ed (low or high pressure switches, or compressor internal over-load). If any compressor safety device opens, the compressorwill stop. High and low-pressure switches and compressor mo-tor overload protectors will reset automatically when the condi-tion which caused the device to trip has dropped below the re-set condition. To reset the Cycle-LOC control device, manuallyturn the control power OFF, then back ON.SERVICECleaning Evaporator Coil — Do not use high-pressurewater or air. Damage to fins may result. Clean coils with a vac-uum cleaner, fresh water, compressed air, or a bristle brush (notwire). Backflush coil to remove debris. Commercial coil clean-ers may also be used to help remove grease and dirt. Steamcleaning is NOT recommended.Units installed in corrosive environments should be cleanedas part of a planned maintenance schedule. In this type of appli-cation, all accumulations of dirt should be cleaned off the coil.Take care not to get water in the system ducts or unitinsulation.Lubrication — Fan motors have permanently lubricatedbearings.Indoor Fan Adjustment — To prevent personal injury,be sure wire fan guards (provided by customer) are secured inplace over each fan discharge (or that fans are ducted) beforestarting the unit.TO CHANGE FAN SPEED1. Shut off unit power supply. Lock out power supply andtag disconnect locations.2. Loosen fan belt by loosening fan motor belt adjustingbolts. Do not loosen fan motor mounting bracket fromunit.3. Loosen movable pulley flange setscrew (Fig. 11).4. Screw movable flange toward fixed flange to increase fanspeed and away from fixed flange to decrease speed. In-creasing fan speed increases load on motor. Do not ex-ceed maximum allowable fan speed or motor full loadamps indicated on unit nameplate and in Table 5.5. Set movable flange setscrew at nearest flat of pulley huband tighten setscrew.6. Check pulley alignment and belt tension adjustment asdescribed below.7. Check fan operation. Repeat above procedure as required.Pulley Alignment — Shut off unit power supply. Lockout power supply and tag disconnect locations. Loosen fanmotor pulley setscrews and slide fan pulley along fan shaft.Make angular alignment by loosening motor from mountingbracket (see Fig. 11). Check alignment with a straightedge.Belt Tension Adjustment — Shut off unit power sup-ply. Lock out power supply and tag disconnect locations. Loos-en fan motor mounting plate bolts. Do not loosen motormounting bracket from unit. Adjust belt tensioning bolt untilproper belt tension is obtained.Changing Fan Wheel — If a fan wheel should fail, itmay be replaced as follows:1. Shut off unit power supply. Lock out power supply andtag disconnect locations.2. Remove belts from fan pulley.3. Loosen locking collars on the fan bearings and set screwson the fan wheels.4. Remove the shaft through the access panel on either sideof the unit.5. Remove the fan cut-off plate in the fan discharge.6. Remove the fan wheel through the fan discharge opening.7. Replace the wheel, and reverse Steps 1-5 above.Fan Bearing Replacement — If a fan bearing fails,replace it as follows:1. Shut off unit power supply. Lock out power supply andtag disconnect locations.2. Remove belts from the fan pulley.3. Support fan shaft.4. Loosen locking collar on fan bearing.5. Remove bearing from the shaft.6. Install new bearing onto the shaft, and reverse Steps 1-3above.