Apparatus and method of oil charge loss protection for compressors

A method for monitoring oil charge loss in a refrigeration system having a compressor for compressing a refrigerant gas, an oil/gas separator for separating compressed refrigerant from lubricating oil, a condenser for condensing the compressed refrigerant gas, an oil cooler for cooling liquid oil separated from the refrigerant gas, the refrigerant and the liquid oil both having known and differing coefficients of heat transfer, and an injection system for injecting the cooled oil into the compressor, comprising the steps of:

• a. determining a temperature standard of the liquid for the oil cooler and an acceptable standard of deviation from the temperature standard;
• b. sensing the temperature of the liquid at the oil cooler;
• c. comparing the temperature of the liquid at the oil cooler and the temperature standard;
• and
• e. generating a signal to shut down the compressor when the comparison of the temperature of the liquid at the oil cooler is outside the acceptable standard of deviation from the temperature standard;
• wherein the temperature standard is a function of the temperature of the saturated refrigerant at the condenser and the acceptable deviation of the temperature from the temperature is a function of the temperature of refrigerant cooled in the oil cooler sensed at the oil cooler.

An oil charge loss detector in air conditioning system having a compressor for compressing a refrigerant gas, an oil/gas separator for separating compressed refrigerant gas from lubricating oil, a condenser for condensing the refrigerant gas to high pressure liquid, an oil/gas separator for separating the liquid oil from the refrigerant gas, an oil cooler for cooling the liquid oil, and an injection system for injecting the cooled oil into the compressor, the oil and the refrigerant having a known and differing coefficients of heat transfer, comprising:

• a. means for sensing the temperature of the saturated refrigerant exiting the compressor;
• b. means for determining a temperature standard of the liquid at the oil cooler and an acceptable standard of deviation from the temperature standard as a function of the sensed saturated refrigerant;
• c. sensing means for sensing the temperature of the liquid at the oil cooler;
• d. means for comparing the temperature of the liquid at the oil cooler and the temperature standard;
• and
• e. means for generating a signal to shut down the compressor when the comparison of the temperature of the liquid at the oil cooler is outside the acceptable standard of deviation from the temperature standard.

An oil charge loss detector for use with a refrigeration system having a compressor being adapted for compressing a refrigerant gas and being lubricated by oil that is intermixed with the refrigerant gas, a condenser adapted for removing heat from the compressed refrigerant gas and condensing the refrigerant gas to a liquid, a oil cooler for cooling a liquid therein, the oil cooler being filled with oil under normal operating conditions and filling with refrigerant upon the occurrence of an oil charge loss to the refrigeration system, the oil and the refrigerant having known and differing coefficients of heat transfer, the loss detector comprising:

• means for determining a temperature standard as a function of calculating the difference in the temperature of oil cooled in the oil cooler and refrigerant cooled in the oil cooler as a function of the coefficients of heat transfer of the oil and the refrigerant with and respect to the saturated refrigerant liquid temperature in the condenser at any given operating condition of the condenser;
• sensing means for sensing the temperature of the liquid cooled in the oil cooler;
• sensing means for sensing the saturated refrigerant temperature in the condenser;
• and
• means for generating a compressor shut down command when the temperature differential of the temperature of the liquid in the oil cooler and the saturated refrigerant temperature in the condenser deviates from the temperature standard.

A method of determining loss of lubricant in a compressor providing a compressed refrigerant to a condenser, the method comprising the steps of:

• measuring a first temperature representative of the refrigerant fluid exiting the compressor;
• measuring a second temperature representative of a lubricant entering the compressor;
• comparing the first temperature to the second temperature;
• and
• terminating compressor operation if the temperature differential between the first and second temperatures substantially deviates from a predetermined temperature differential.