Refrigeration system

An air conditioning system comprising:

• a duct defining therein an air passage having a downstream end open to a chamber to be air-conditioned;
• a refrigeration system including:
• a variable capacity refrigerant compressor including means for varying the displacement of said compressor and means for driving said compressor displacement varying means;
• and an evaporator disposed in said air passage and being in fluid-flow communication with the intake side of said compressor;
• means for causing air to flow through said evaporator and through said duct into said chamber;
• a heater disposed in said duct downstream of said evaporator and being operative to heat at least a part of the air which has passed through said evaporator;
• means for controlling the heating of the air by said heater;
• and
• means for controlling the capacity of said compressor, said capacity controlling means including:
• sensor means operative to detect a condition related to the cooling operation of said evaporator and emit a first electric signal representing the condition thus detected;
• means for detecting the position of said air heating controlling means to emit a second electric signal representing the position thus detected;
• and
• electric circuit means operative in response to said first and second electric signals from said sensor means and from said position detecting means to actuate said driving means for thereby varying the displacement of said compressor whereby the capacity of said refrigeration system can be controlled, said electric circuit means including:
• (a) means emitting a third electric signal in accordance with the ratio between said first and second electric signals;
• (b) a first comparator means operative to compare said third electric signal with a first electric reference signal to emit a first electric output;
• (c) a second comparator means operative to compare said third electric signal with a second electric reference signal different from said first electric reference signal to emit a second electric output;
• (d) first electric actuating means responsive to said first electric output to actuate said driving means in a direction to decrease the compressor displacement;
• and
• (e) a second electric actuating means responsive to said second electric output to actuate said driving means in a direction to increase the compressor displacement.