Midea MSY-09HRDN1-QC8 Service Manual page 31

8.7.5 Indoor heat exchanger high temperature protection.
If T2＞60℃, the compressor will stop and not resume until T2＜48℃.
8.7.6 Defrosting mode.
Condition of defrosting.
Condition 1: If T4＞0℃,
When the units are running, if the following two items are satisfied the units start defrosting:
The units runs with T3＜3℃ for 40 minutes and T3 keeps lower than -6℃ for more than 3 minutes.
The units runs with T3＜3℃ for 80 minutes and T3 keeps lower than -4℃ for more than 3 minutes.
Condition 2: If T4＜0℃,
The program judges according to the condition 1, if the two items are satisfied, then judges if T2 has
descended for more than 5℃, if it has the machine starts defrosting, or continues to judge T2 and will
not defrost until T2 drops more than 5℃.
Condition 3: No matter what value T4 is, if the machine runs with T3＜3℃ for more than 120 minutes
and T3 keeps lower than -2℃ for more than 3 minutes, the machine will defrost, no matter if T2 drops
for more than 5℃ or not.
Condition of ending defrosting.
If any one of following items is satisfied, defrosting will finish and the machine will turn to normal
heating mode.
T3 rises to be higher than 12℃.
T3 rises to be higher than 8℃ and remains for 80 seconds.
The machine has run for 10 minutes in defrosting.
8.7.7 Defrosting action
For MSY-09HRDN1-QC2 and MSY-12HRDN1-QC2
I3HEAT
I2HEAT
I1HEAT
comp. pause
freq. descends if curr. rises;
freq. remains if curr. descends
running normally
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