Stimmen - 4, Durchschnittliche Bewertung: 4.3 ( )

Hersteller: Bryant Dateigröße: 1.16 mb Dateiname: Unterrichtssprache:

Defrost is achieved with a timer set to initiate defrost every 30, 50, or 90 minutes (factory set at 30 minutes). Defrost is initiated when refrigerant temperature leaving the outdoor coil is measured below 27 F, (typically when the outdoor ambient temperature is below 45 F as sensed by the defrost thermostat [DFT]). Defrost is terminated when: The refrigerant temperature rises to 80 F at the DFT location on the liquid line; or the refrigerant pressure rises to 280 psig at the HPS2 location on the liquid line; or the defrost timer completes the 10-minute cycle. IV. DUPLEX UNITS A. Duplex 575C120 Units with 524A-H240 (See Fig. 12) Cooling When the thermostat is set for cooling, and the space temperature comes within 2° F of the cooling set point, the thermostat completes the circuit from R to O and the reversing valves in both units are energized. If the space temperature continues to rise, the circuit from R to Y1 is completed. If the time delays and safeties are satisfied, the compressor contactor closes, starting the compressor and outdoor-fan motors of Heat Pump A. At the same time the circuit is completed from R to G, starting the indoor-fan motor. If the space temperature continues to rise, the circuit is completed from R to Y2 and the Cooling mode is initiated in Heat Pump B in a similar manner. When the thermostat is satisfied, the contacts open, deenergizing first the Heat Pump B and then Heat Pump A. Heating When the thermostat calls for heating, the circuit from R to Y1 is completed. If the time delays and safeties are satisfied, the compressor contactor closes, starting the compressor and outdoor-fan motors of Heat Pump A and Heat Pump B. At the same time the circuit is completed from R to G, starting the indoor-fan motor. If the second stage of heating is required, the circuit from R to W2 will be completed and the electric resistance heaters will be energized. When the thermostat is satisfied, the contacts open, deener gizing Heat Pump A and Heat Pump B. B. Duplex 575C120 and 541A180 Units With 524A-H300 (See Fig. 13) Cooling When the thermostat calls for cooling, the circuit from R to Y1 is completed. If the time delays and safeties are satisfied, the compressor contactor closes, starting the compressor and outdoor-fan motors of Heat Pump A (541A180). At the same time the circuit is completed from R to G, starting the indoor- fan motor. If the space temperature continues to rise, the circuit is completed from R to Y2 and the Cooling mode is initiated in Heat Pump B (575C120). When the thermostat is satisfied, the contacts open, deenergizing first the Heat Pump B and then Heat Pump A. Heating When the thermostat calls for heating, the circuit from R to W1 is completed. If the time delays and safeties are satisfied, the compressor contactor closes, starting the compressor and outdoor-fan motors of Heat Pump A and Heat Pump B. At the same time the circuit is completed from R to G, starting the indoor-fan motor. If the second stage of heating is required, the circuit from R to W2 will be completed and the electric resistance heaters will be energized. When the thermostat is satisfied, the contacts open, deener gizing Heat Pump A and Heat Pump B. C. Safeties The high-pressure switch, loss-of-charge switch, oil pressure safety switch, and compressor overtemperature safety are located in a CLO circuit that prevents heat pump operation if these safety devices are activated. A light at the thermostat energizes when CLO circuit is affected. The lockout system can be reset by adjusting the thermostat to open the contacts (down for Heating mode, up for Cooling mode), deenergizing the CLO circuitry. Compressor overcurrent protection is achieved with a circuit breaker which requires manual resetting at the outdoor unit control box. The unit is equipped with an oil pressure safety switch that protects the compressor if oil pressure does not develop on start-up or is lost during operation. The oil pressure switch is of the manual reset type and therefore must be reset at the outdoor unit. DO NOT RESET MORE THAN ONCE. If oil pressure switch trips, determine cause and correct. DO NOT JUMPER OIL PRESSURE SAFETY SWITCH. To reset the oil pressure switch: 1. Disconnect power to the unit. 2. Press the RESET button on the oil pressure switch. 3. Reconnect power to the unit. —19— Unit is equipped with a no-dump reversing valve circuit. When unit is in Cooling mode, reversing valve remains in cooling position until a call for heating is requested by thermostat. When unit is in Heating mode, reversing valve remains in heating position until there is a call for cooling. The crankcase heater is in a lockout circuit. If crankcase heater is defective, compressor is locked off. Heat pump remains off until corrective action is taken. The lockout circuit cannot be reactivated by adjusting the thermostat. To reset the crankcase heater lockout, disconnect and then reconnect power to unit. D. Check Operation Ensure operation of a...

Herunterladen

Geben Sie zwei Ziffern: