The high pressure line of the AC is very hot. This is what the condenser coil is just a high pressure line. It's very hot and needs to be cooled to raise the efficiency of the unit. This is why there is a fan pulling air through the coil. What this unit does is cool the condenser coil by using the pool water in a gas to water heat exchanger. As this is done with a very small pump that runs 24hrs a day. The water pump is the size of a soda can. Since the coil is cool this means the fan on the condenser unit does not need to turn on. There is a thermal switch that controls the fan.