McQuay MQS-24018-CFC216A Installation And Operation Manual page 11

In Summary：
After t mins of operation of the compressor under "heating" mode, defrosting starts when the defrosting
thermistor indicates the temperature below T1 for 1 min. Meanwhile, the 4-way valve is energized, the fan motor of
outdoor unit stops running and the auxiliary electric heating device is powered. The defrosting will stop after it
operates for 10 consecutive minutes or the temp sensor detects the ambient temperature over T2 . At the same time,
the 4-way valve is re-energized, the fan motor of outdoor unit powered and the auxiliary electric heating device runs
as per the setting of wired controller.
The defrosting stops as soon as the A/C is diverted to "COOLING" mode while the outdoor unit defrosting.
Forced Defrosting:
By pressing the forced defrosting button, the A/C starts to defrost promptly. At the same time, the 4-way valve
is energized, the fan motor of outdoor unit stops running and the auxiliary electric heating device is powered. The
defrosting will stop after it goes on for 10 minutes or the temp sensor detects the ambient temperature over T2.
Meanwhile, the 4-way valve is re-energized, the fan motor of outdoor unit is electrified and the auxiliary electric
heating device runs as per the setting of the wired controller.
DIP Switch (SA1):
WARNING:
The default setting of DIP switch in the WZ14301 -1 main board of the outdoor unit is 000.
NOTE：
1
（The number port refers to "1", the ON port to "0"）
Normal Operation
Main Board LED Display Instruction
Defrosting
0
LED1
Flashing every 0.5s
On
7
LED2
Flashing every 0.5s
On