Évaluations - 4, GPA: 4.3 ( )

Fabricant : Carrier Taille : 996 kb Nom Fichier : Langue d'enseignement:

Heater musi be tight to prevent backing out (heater will burn out if exposed to air). The heater is wired into compressor control circuit through a relay to energize only when compressor shuts off. This keeps the oil at a temperature that will prevent excessive absorption of refrigerant during shutdown periods. Crankcase heater is located in a lockout circuit. If crankcase heater is defective, the compressor locks off Heat pump remains off until corrective action is taken. This lockout circuit cannot be reset by adjusting the thermostat. Crankcase heater should be energized at all times when unit is not running except during prolonged shutdown or during servicing. In these cases, heater should be energized for 24 hours before unit is restarted. Fan Motor Protection — Fan motors are inherently protected, grouped on a single circuit breaker. Fan Adjustment — When replacing a fan, adjust fan until top surface of hub plate is below top of orifice ring as indicated in Fig 11. Then, tighten both setscrews, located over the keyway of fan hub of motor shaft. Seal recessed area of fan hub bore with Permagum to prevent rusting. Head Pressure Control reduces condensing capacity under low-ambient conditions. For intermediate season operation, fan cycling is employed. Fan no. 2 is cycled by pressure control, with the pressure sensor located in the liquid line. Fan no. 3 is cycled by an air temperature thermostat (see Table 2). Liquid Line Solenoid Valve closes when compressor is off, and opens when compressor is on. The valve minimizes refrigerant migration during heat pump OFF cycle, protecting against flooded starts. Accumulator Oil Return is external. The accumulator drains through an extenal port at bottom of accumulator. The port feeds an orifice which regulates the rate of oil and refrigerant returned to the compressor. The orifice is removable and cleanable when the system does not contain refrigerant. The oil return mechanism also contains a solenoid valve that opens when compressor is ON, and closes when compressor is OFF. The oil return solenoid does not allow liquid refrigerant to drain from the accumulator during the heat pump OFF cycle, protecting the compressor against flooded starts. Lubrication FAN MOTORS — Fan motors have permanently lubricated bearings. No provisions for lubrication are made. COMPRESSOR — The compressor has its own oil supply. Loss of oil due to a leak in the system should be the only reason for adding oil after system has been in operation. Coil Cleaning — Clean coils with a vacuum cleaner, fresh water, compressed air or a bristle brush (not wire). Set up coil cleaning as part of a planned maintenance schedule when units are installed in corrosive environments. Wash all accumulations of dirt from coil in these applications. Keep condenser coil drain holes free of dirt and debris to ensure adequate coil drainage. UNIT DIMENSION A (in.) 38AQ Center Fan End Fan 024 3/4 % 028 034 1% 2% Fig. 11 — Fan Adjustment 9 OPERATING SEQUENCE (Refer to wiring diagrams in 38AQ wiring booklet) Standby (OFF) Mode — During the standby or OFF mode, crankcase heater is energized. Reversing valve may or may not be energized depending on mode of operation (heating or cooling) when thermostat is satisfied. COOLING — When thermostat calls for first-stage cooling (TCI closed), indoor fan motor starts immediately. Compressor and outdoor fans start between 3 seconds and 5 minutes depending on length of time unit is off after thermostat is satisfied, due to 5-minute Time Guard® II circuit. Outdoor fan motors nos. 2 and 3 may or may not operate depending on position of fan cycling pressure switch (FCPS) and air temperature switch (ATS). The reversing valve solenoid (RVS) becomes deenergized causing reversing valve to shift to cooling position. Crankcase heater is off. Liquid line and accumulator oil return solenoid valves open, allowing refrigerant and oil flow. Defrost Timer does not operate during cooling mode. When thermostat calls for second-stage cooling (TC2 closed), unloader is de-energized causing compressor to run fully loaded. If a malfunction occurs, causing high-pressure switch (HPS) discharge gas thermostat (DGT) or loss-of-charge switch (LCS) to open, compressor and outdoor fans stop and are locked out by a Signal-Loc circuit, and a warning light comes on at the thermostat. RVS remains de-energized so reversing valve does not shift. These safeties reset by adjusting thermostat up to open TCI and TC2, or by momentarily switching subbase to OFF position. When thermostat is satisfied (TCI open), compressor, indoor fan motors shut off. Liquid line and accumulator oil return solenoid valves close. Reversing valve does not shift, but remains in cooling position until there is a call for heating. If compressor oil pressure is lost, or if oil pressure fails to build on start-up, an oil pressure safety switch shuts down unit. Switch must be manually reset at the unit. DO NOT RESET MORE T...

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