Small tuning changes to the system....

7 June : Two small changes recently:-  I added a pushbutton switch that allows me to force the system on even when the thermostat says No! This allows me to read the digital clock.
     But also, it enables me to kickstart the system when there is warm glycol in the panels, but everytime warmed glycol rushes down from the sunboxes, it changes the delta-T and turns the sunboxes off again. This only happens when the air temperature in the sunboxes is less than 20ºC. This often happens on cold cloudy days or in the early evening.
    To make the Delta-T less of a hindrance, I reduced it to 4 degsC, instead of the 5 degs that I have used since March.
    The algorithm in the heat pump's controller likes to calculate the outgoing glycol to construct a difference of about 3.6 degC between the input and output temperatures. This makes me think that while I can reduce the delta-T to 4.0, I should not be tempted to reduce it to anything less than 3.6 degsC. There has to be enough delta-T to push energy from the air temp into the moving liquid in the panels, through a wall of polypropylene.