Heat pump compressor crankcase low differential temperature detection and control system

Claim 1

A compressor crankcase low differential temperature detection and control system (hereinafter "control system") for a reverse cycle refrigeration system (hereinafter "system") for heating and cooling an enclosure wherein said system comprises refrigerant compression means including crankcase heating means, refrigerant compression control means, an indoor coil, an outdoor coil, and refrigerant conduit means connecting said compression means and said coils, said control system comprising: outdoor air temperature sensing means (hereinafter "TODAS") having an output indicative of outdoor air temperature (hereinafter "TODA"); compressor crankcase temperature sensing means (hereinafter "TCCS") having an output indicative of the temperature (hereinafter "TCC") of the crankcase of said refrigerant compression means; enclosure temperature sensing means (hereinafter "STAT") having an output indicative of a demand for heating or cooling of the enclosure; and controller means having operative connections to said TODAS, TCCS, and STAT so as to receive the outputs thereof, said controller means including circuit connect-disconnect means selectively interconnecting said STAT output to said refrigerant compression control means whereby, when said STAT output is connected thereto, said compression means is enabled to operate in response to a demand from said STAT for heating or cooling and, when said STAT output is disconnected therefrom, said compression means is inhibited from operating, said controller means being effective to inhibit said compression means from operating whenever the value of TCC minus TODA is less than a preselected amount, and said controller means being further characterized by permitting operation of said compression means whenever TODA is greater than a predetermined value.