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Control System 1

Simple PID control system for heat pump.

Note: This control system is expected not to work very well for a PID control system, due to instability problems.
(Not yet tested.)

Fig 1 - Simple heatpump control system.

This simple control system is expected to work ok if the control loop for the compressor is just a simple on/off regulator.

If on he other hand, the control loop for the compressor is a PID continius regulator, this is expected to be working not so
well, due to instability problems and missmatch in time constants between the condenser and evaporator control loop.
Fig 2 - The pressure/temperature loop for the evaporator.

Above: A basic control loop for an evaporator. The evaporator control loop consists of a simple pneumatic-mechanical
P-regulator. Variations in input press from the condenser and variations suction pressure should lead to process
instability to the evaporator control loop.

Under: The control loop for room temperature. Expected to work OK for a simple on/off control loop, but not for a PID
control loop. (Not yet tested.) 

Fig 3 - The room temperature control loop.