Friedrich MRM09Y1J, Service & Parts Manual

Page: 35 / 135

35 PB
OPERATION
9-12k Sequence of Operation
Overheating Control
Heat Pump Only
During heating operation, the signals being sent from the indoor unit allow the operating frequency limitation and prevent abnormal
high pressure. (The signal from the indoor unit must be divided as follows.)
1.Conditions for Start Controlling
Judge the controlling start with the indoor heat exchanger temperature after 2 seconds from operation start.
2.Control in Each Zone
The heat exchange intermediate temperature of indoor unit controls the following.
Defrost Control
Heat Pump Only
Defrosting is carried out by the cooling cycle (reverse cycle). The defrosting time or outdoor heat exchanger temperature is dependent
Reset zone
Up zone
Keep zone
Dropping zone
Stop zone
1.Conditions for Starting Defrost
The starting conditions must be made with the outdoor ambient air sensor (outdoor air temperature) and indoor coil sensor
2.Conditions for Canceling Defrost
Current indoor coil sensor (heat exchanger temperature) is between 39°F~72°F)
Heat exchanger
thermistor temperature
Compressor
Frequency
Fan
Electronic expansion
Four way valve
ON
valve opening
OFF
ON
OFF
ON
OFF
0Hz
5sec.
350pps 450pps 450pps
Initial opening
PI control
5sec.
50sec. 50sec. 600sec.
60sec.
on specific conditions being met or satisfied before releasing defrost.
(heat exchanger temperature). When the system is in heating operation for 6 minutes after the compressor is started or more than 45
minutes of accumulated time has passed since he start of operation or ending the defrost cycle