Midea MS9A-09HRDN1-QC2 Service Manual page 29

Zone D: Compressor stops after running with F1 for 60 minutes or when ΔTh＞6℃.
9.7.4 Outdoor unit current control in heating mode.
9.7.5 Indoor heat exchanger high temperature protection.
If T2＞60℃, the compressor will stop and not resume until T2＜48℃.
9.7.6 Defrosting mode.
1) Condition of defrosting.
Condition 1: If T4＞0℃,
When the units are running, if the following two items are satisfied the units start defrosting:
3 minutes.
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.
2) Condition of ending defrosting.
If any one of following items is satisfied, defrosting will finish and the machine will turn to normal heating
mode.
a) T3 rises to be higher than 12℃.
I3HEAT
I2HEAT
I1HEAT
a) The units runs with T3＜3℃ for 40 minutes and T3 keeps lower than -6℃ for more than
b) The units runs with T3＜3℃ for 80 minutes and T3 keeps lower than -4℃ for more than
comp. pause
freq. descends if curr. rises;
freq. remains if curr. descends
running normally
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