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View Full Version : Why does one outdoor fan shut off in heat cycle?







JCole21961
04-06-2014, 11:11 PM
I have two Hitachi 5T heat pumps. Each outdoor unit has two fans. One of these is controlled by a pressure switch and shuts off at times. Why is this? I would think the unit needs all the air possible in order to extract as much heat as possible. Note that this is not the defrost mode when both fans stop.

Tayters
04-06-2014, 11:23 PM
Don't know about the specifics of a Hitachi but older Fujitsu's I seem to recall would do it so as to control the temperature of the indoor coil. If indoor coil was getting too hot (over 60*C roughly) outdoor fan would slow down to reduce capacity then stop if coil temp got to a certain level.

Cheers,
Andy.

JCole21961
05-06-2014, 03:41 PM
In this case there is no temperature sensor on the indoor coil. The fan is controlled by a pressure switch on the refrigerant line. I'm not sure if it on the high or low side. I cannot see any reason to shut down one fan except for defrost, when both stop.

frank
06-06-2014, 10:00 PM
In this case there is no temperature sensor on the indoor coil. The fan is controlled by a pressure switch on the refrigerant line. I'm not sure if it on the high or low side. I cannot see any reason to shut down one fan except for defrost, when both stop.
it's called superheat control