Crank case heater control

Abstract

A control system for a crank case heater for an inverter operated compressor of a cooling system includes a contactor operably connected to the crank case heater and an inverter controller compressor and at least one compressor temperature sensor disposed at the compressor to sense a compressor temperature and an compressor internal temperature sensor. A controller is operably connected to the crank case heater and the at least one compressor temperature sensor and configured to close the contactor to energize the crank case heater independently from operation of the compressor when the at least one compressor temperature sensor senses a compressor temperature below a desired threshold.

1 . A control system for a crank case heater for a compressor of a cooling system comprising:
 a contactor operably connected to the crank case heater, the inverter and indirectly to the compressor;   at least one compressor temperature sensor disposed at the compressor to sense a compressor temperature;   a first temperature switch located in air space; and   a controller operably connected to the crank case heater and the at least one compressor temperature sensor and configured to close the contactor to energize the crank case heater when the at least one compressor temperature sensor senses a compressor temperature below a desired threshold; and   a second temperature switch located at a discharge line of the compressor to energize the crank case heater when a discharge line temperature is below a desired lower limit and the compressor is not operating.   
     
     
         2 . The control system of  claim 1 , wherein the controller is operably connected to the compressor. 
     
     
         3 . The control system of  claim 2 , wherein the controller is configured to energize the compressor independently of the crank case heater via the second temperature switch. 
     
     
         4 . The control system of  claim 2 , wherein the controller is operably connected to the compressor via the inverter. 
     
     
         5 . The control system of  claim 1 , wherein at least one compressor temperature sensor is disposed internal to the compressor. 
     
     
         6 . The control system of  claim 1 , wherein the first temperature switch is in an indoor ambient air space. 
     
     
         7 . The control system of  claim 1  wherein the first temperature switch is in an outdoor ambient air space. 
     
     
         8 . The control system of  claim 1 , wherein the threshold is determined relative to the lesser of a dwelling temperature and an outdoor ambient temperature plus a differential value. 
     
     
         9 . The control system of  claim 8 , further comprising at least one dwelling temperature sensor operably connected to the controller. 
     
     
         10 . The control system of  claim 8 , further comprising at least one ambient temperature sensor operably connected to the controller. 
     
     
         11 . A cooling system comprising:
 a compressor;   an inverter   a crank case heater disposed at the compressor;   a contactor operably connected to the inverter and the crank case heater;   at least one compressor temperature sensor disposed at the compressor to sense a compressor temperature; and   a controller operably connected to the crank case heater and the at least one compressor temperature sensor and configured to close the contactor to energize the crank case heater when the at least one compressor temperature sensor senses a compressor temperature below a desired threshold; and   a temperature switch located at a discharge line of the compressor to energize the crank case heater when a discharge line temperature is below a desired lower limit and the compressor is not operating.   
     
     
         12 . The cooling system of  claim 11 , wherein the controller is operably connected to the inverter. 
     
     
         13 . The cooling system of  claim 12 , wherein the controller is configured to energize the compressor independent of operation of the crank case heater. 
     
     
         14 . The cooling system of  claim 12 , wherein the controller is operably connected to the compressor via an inverter. 
     
     
         15 . The cooling system of  claim 14 , wherein the inverter is connected to the contactor. 
     
     
         16 . The cooling system of  claim 11 , wherein the at least one compressor temperature sensor is disposed internal to the compressor. 
     
     
         17 . The cooling system of  claim 11 , further comprising at least one dwelling temperature sensor operably connected to the controller. 
     
     
         18 . The cooling system of  claim 11 , further comprising at least one outdoor ambient temperature sensor operably connected to the controller. 
     
     
         19 . A method of controlling operation of a crank case heater for a compressor of a cooling system comprising:
 sensing a compressor temperature;   determining if the compressor temperature is below a desired threshold;   closing a contactor operably connected to the compressor and the crank case heater, thereby energizing the crank case heater if the compressor temperature is below the desired threshold;   wherein energizing of the crank case heater is independent of operation of the compressor.   
     
     
         20 . The method of  claim 19 , further comprising deengerizing the crank case heater when the compressor temperature is above the desired threshold. 
     
     
         21 . The method of  claim 19 , further comprising deengerizing the crank case heater when the compressor discharge line temperature is above the desired threshold. 
     
     
         22 . The method of  claim 19 , wherein the threshold is determined relative to the lesser of a dwelling temperature and an outdoor ambient temperature.