
www.freedomhp.co.uk
©G Hendra Nov 18
5
What makes the unit go?
When operating the unit measures the water flow and return temperatures across the
outdoor heat exchanger. T/S 2 and T/S1 in the diagram below.
If the delta T (temp difference across T/S1 and T/S2) is 5 degrees C the unit is
happy, this is its main control feature.
If T/S 2 (flow) is less than 5 c above T/S1 (return) the unit is providing too much heat
so the compressor will slow down reducing capacity.
If T/S 2 (flow) is more than 5 C above T/S1 (return) the unit needs to work harder so
it will rev up.