Heat pump with improved performance during cold outdoor temperatures

Abstract

A heat pump system that achieves improved performance in cold weather by slowing the indoor blower motor in response to reduced temperature or pressure of the indoor liquid refrigerant line is described. A pressure transducer or temperature sensor on the indoor refrigerant line sends an electrical signal to a variable speed drive controlling the indoor blower motor, so that the indoor blower motor maintains normal speed during cooling or defrosting mode. The signal input from the pressure transducer or temperature sensor commands the variable frequency drive control to slow the fan motor down or speed it up by modifying the voltage and the frequency to the indoor motor. As a result, the indoor air handler motor slows down or speeds up to maintain the head pressure at optimal performance.

1 . A heat pump system comprising:
 a compressor;   an indoor coil and an outdoor coil connected to the compressor and connected to each other in a circuit by way of a liquid line comprising a liquid;   a reversing valve connected with the liquid line for reversing flow of the liquid;   an indoor blower motor configured to blow air across the indoor coil;   a variable speed drive in operable connection with the indoor blower motor; and   a sensor configured for measuring pressure or temperature of the liquid in an indoor portion of the liquid line;   wherein the sensor is operably configured to send an electrical signal to the variable speed drive; and   wherein the variable speed drive is operably configured to send a reduced electrical signal to the blower motor in response to a reduced electrical signal from the sensor thereby reducing speed of the indoor blower motor.   
     
     
         2 . The system of  claim 1 , wherein the variable speed drive is operably configured to send an electrical signal to the indoor blower motor that is reduced in voltage or hertz in response to a reduced electrical signal from the sensor. 
     
     
         3 . The system of  claim 1  further comprising a thermostat operably configured to send an electrical signal to the variable speed drive during cooling mode. 
     
     
         4 . The system of  claim 3 , wherein the variable speed drive is configured to operate the indoor blower motor at full speed during cooling mode in response to the electrical signal from the thermostat. 
     
     
         5 . The system of  claim 4 , wherein the thermostat is operably configured to send a 24 volt signal to the variable speed drive during cooling mode. 
     
     
         6 . The system of  claim 1 , wherein the sensor is operably configured to send a 4 to 20 milliamp or 0 to 10 volts DC signal to the variable speed drive. 
     
     
         7 . The system of  claim 6 , wherein the signal from the sensor is proportional to pressure or temperature level of refrigerant in the indoor portion of the liquid line. 
     
     
         8 . The system of  claim 1 , wherein the indoor blower motor is a three-phase motor. 
     
     
         9 . The system of  claim 1 , wherein the indoor blower motor is a one-phase motor. 
     
     
         10 . A method of operating a heat pump system, the method comprising:
 providing a variable speed drive and connecting the variable speed drive to an indoor blower motor of a heat pump;   measuring pressure or temperature of a liquid in an indoor portion of a liquid line connecting an indoor coil, an outdoor coil, and a compressor of the heat pump; and   in response to reduced pressure or temperature over a period of measurement, sending a reduced electrical signal from the variable speed drive to the indoor blower motor, thereby slowing speed of the indoor blower motor.   
     
     
         11 . The method of  claim 10 , wherein the reduced electrical signal from the variable speed drive is reduced in voltage or hertz. 
     
     
         12 . The method of  claim 10  further comprising sending an electrical signal to the variable speed drive during cooling mode. 
     
     
         13 . The method of  claim 12  further comprising operating the indoor blower motor at full speed during cooling mode in response to the electrical signal. 
     
     
         14 . The method of  claim 13  further comprising sending a 24 volt signal to the variable speed drive during cooling mode. 
     
     
         15 . The method of  claim 10  further comprising sending a 4 to 20 milliamps or a 0 to 10 volt DC signal to the variable speed drive. 
     
     
         16 . The method of  claim 15 , wherein the signal is proportional to pressure or temperature of the liquid in the indoor portion of the liquid line. 
     
     
         17 . The method of  claim 10 , wherein the indoor blower motor speed correlates with outdoor temperature such that the indoor blower motor speed is reduced as the outdoor temperature is reduced. 
     
     
         18 . A kit for converting a heat pump system into a higher efficiency heat pump system, the kit comprising:
 a control board or a variable speed drive operably configured for connection with an indoor blower motor of a heat pump; and   a sensor configured for measuring pressure or temperature of a fluid in an indoor portion of a liquid line of the heat pump;   wherein the sensor is operably configured to send an electrical signal to the variable speed drive; and   wherein the variable speed drive is operably configured to send a reduced electrical signal to the blower motor in response to a reduced electrical signal from the sensor thereby reducing speed of the indoor blower motor.