Heating and cooling system with variable capacity compressor

摘要

Compressor discharge temperature, ambient outdoor air temperature and thermal load are used as control parameters for controlling the expansion valve setting and the indoor fan speed. In a variable capacity system the thermal load parameter also controls the compressor capacity. Thermal load is measured by an integrating procedure that increments or decrements an accumulated demand counter value used as an indication of thermal load on the system. The counter value is incremented and decremented based on the room temperature and thermostat setpoint. These same parameters are also used in the overcharge/undercharge diagnostic system.