Control system for maximizing the efficiency of an evaporator coil

A system and control means therefor, comprising:

• a compressor, said compressor including a fluid sump;
• a first coil operatively connected to said compressor;
• a second coil operatively connected to said first coil and to said compressor;
• an electrically operable expansion valve connected between said first and said second coils, said expansion valve including electrically energizable means for controlling the position of said valve;
• and
• control means operatively connected between said system and the electrically energizable means of said expansion valve, said control means including a first sensor for sensing a condition in said system, a second sensor for sensing the same condition in said system at a point displaced from said first sensor, differential means for comparing the condition sensed by said first and said second sensors, said differential comparing means having an input side operatively connected to said first and said second sensors, and an output side, a mixer amplifier having a first input operatively connected to the output of said differential comparing means, and a second input, and override means having an output side forming a second input to said mixer amplifier, said override means including a third sensor for sensing a condition in said system, amplifier means operatively connected to said third sensor, and feedback means connected between the output and the input sides of said amplifier, said feedback means acting to remove the output of said amplifier under certain predetermined conditions sensed by said third sensor, the output side of said mixer amplifier being operatively connected to said electrically energizable means, said control means acting to regulate fluid flow through said expansion valve so as to establish equality in the condition sensed by said first and said second sensors.