AussieFridgie
30-03-2011, 01:27 PM
I've recently been do a good customers home to work on his heat pump pool heater. It's an APAC C023. I'm pretty sure the C in the code designates this unit as a chiller, though the unit has a reversing valve so can heat and also cool. For some reason though, there is a fan speed controller for the outdoor fans, in this case they are the evaporator fans. It measures liquid line pressure and adjusts fan speed accordingly. Condensing temp is around 45c at about 30c ambient (pool water coming in around 26c), but the suction side is down below zero, in fact coil was icing up when I was there. I've also just verified the charge and it's correct. It's a positive coefficent speed controller, so the higher the head pressure the faster the fan speed, but under these conditions the fans are just ticking over drawing .5 amp (normally about 6 full load).
Is this a mistake? In my mind this means the lower the evap temp drops the lower the airflow, therefore exacerbating the problem. To me it would make more sense to have a negative coefficient controller, measuring AFTER the TXV the evaporator pressure.
To get this going I just bridged out the speed controller so the fans run full load, but I want to be able to give my customer the correct information.
I'm only 1 year in the trade so value your experience. Thoughts??
Is this a mistake? In my mind this means the lower the evap temp drops the lower the airflow, therefore exacerbating the problem. To me it would make more sense to have a negative coefficient controller, measuring AFTER the TXV the evaporator pressure.
To get this going I just bridged out the speed controller so the fans run full load, but I want to be able to give my customer the correct information.
I'm only 1 year in the trade so value your experience. Thoughts??