Midea MSC-09HRDN1-QD0(E) Service Manual page 32

9.7.7 Outdoor unit current control in heating mode.
1) The frequency descending is based on current grade, and judges if descending
again or resuming every 2 minutes.
2) If the current descends and stays at frequency remaining zone for 3 minutes, the
frequency will rise a grade. After 3 minutes if stays at this zone still, the frequency will rise a grade again.
9.7.8 Indoor heat exchanger high temperature protection.
1) If T2＞TEH2℃, compressor frequency will be descended one grade every 20 seconds. When it drops to F2, if
T2 is still higher than TEH2℃ and remains 3 minutes, the compressor will stop.
2) If T2 descends to be lower than 48℃, or remains between 48℃ to TEH2℃ for 6 minutes, frequency limit will
be released.
3) If T2＞60℃, the compressor will stop and not resume until T2＜48℃.
9.7.9 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:
a) The units runs with T3＜3℃ for 40 minutes and T3 keeps lower than TCDI℃ for more than 3 minutes.
b) The units runs with T3＜3℃ for 80 minutes and T3 keeps lower than (TCDI+2) ℃ for more than 3
minutes.
Remark: The above means that when T3 is lower than 3℃ PCB begins to time, if T3 is lower than start
temperature for 3 minutes, the machine starts defrosting. Here start temperature are TCDI ℃and
(TCDI+2) ℃.
Condition 2.
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
℃
5.0
4.5
3.5
3.0
2.5
2.0
1.5
1.0
0.5
Remark: ΔTcon can be changed among 0, -2,- 4 , the default is 0
I3HEAT
I2HEAT
I1HEAT
If T4＜0℃,
H
G
F
E
D
C
B
A
℃ ℃
comp. pause
freq. descends if curr. rises;
freq. remains if curr. descends
running normally
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