Operational Frequency Range; Heat Defrosting Control; Conditions To Enter Defrosting Mode; High Pressure Protection Control On Heat Mode - Mitsubishi Electric MSH09TW Service Manual

10-13. Operational frequency range

Number of
COOL (Hz)
capacity
operating
code
Min.
unit
2
3
1 18
4
4
5
2
6
20
7
8
6
7
3
30
8
9

10-14. Heat defrosting control

(1) Conditions to enter defrosting mode

1. When temperature of defrosting thermistor is 26.6°F or less.
2.When specified non-defrosting time, is counted in the control p.c.board is satisfied.
(Total time of compressor operating)
Going to defrosting mode at both condition of 1 and 2.
(2) Defrosting operation
1. Compressor stops for 50 seconds, Indoor fan is off, Defrosting lamp lights
2.4-way valve reverses flow, Compressor operates by the frequency in heat defrosting control.
3. After compressor stops for 35 seconds, 4-way valve reverses flow, then defrosting finishes.
(3) Conditions to finish defrosting mode
1. When the defrosting thermistor temperature is 46.4°F or more.
2. When it has spent 10 minutes for defrosting.
Defrosting finishes at condition of 1 or 2.
10-15. High pressure protection

(1) High pressure protection control on heat mode

Temperature of the main pipe temp. thermistor in the indoor unit controls the operation frequency.
When temperature of the main pipe temp. thermistor is approx. 120.0°F, the operation frequency is set at the current level.
When temperature of the main pipe temp. thermistor is approx. 125.6°F the protection control decreases the frequency at the
speed of 3Hz a minutes.
When temperature of the main pipe temp. thermistor is approx. 134.6°F the protection decreases the frequency at the speed
of 4Hz a minute and changes the outdoor fan to Low.
Note: Temperature of the pipe temp. thermistor is different depending on the indoor unit.
Temperature of the pipe temp. thermistor is 113°F or less, the protection control is Released.
(2) High pressure protection control by high pressure switch (H.P.S 63H1)
High-pressure switch controls the operation frequency and outdoor fan motor.
<Control status>
When high-pressure switch is ON.
(When discharge pipe pressure is 398.8 PSIG or more.)
<Control details>
(a) When cooling or drying
The protection control decreases the compressor frequency at the speed of 10Hz a minute.
(The compressor operates continuously in min. frequency according to a command to decrease more than the min. level.)
(b) When heating
The protection control decreases the compressor frequency at the speed of 10Hz a minute.
The protection control changes the outdoor fan to Low.
DRY
(Hz)
Max. Rated Min.
52 33
68 46 25 18
85 73
105 80
40 22
110 90
120 104 58 26
Note
• Limit the maximum frequency by means
HEAT (Hz)
of fan speed
Max. Defrost Rated
When all the indoor units in their operation
70 70 49
are running in the same operation mode and
80 80 65
when their fan speed is set to "Low," the
86 86 80
maximum frequency is limited to 6/7 the
rated frequency in the mode.
90 100 88
•Limit the maximum frequency by means of
operation mode
110 100 100
When some indoor units are operating in cool
mode while others are in dry mode, the
maximum frequency, which has the highest
frequency of all the operation mode, is limited
120 100 98
as the table below:
DRY COOL
1
1
2
70
Maximum frequency
1 8/10 of maximum frequency
2 9/10 of maximum frequency
1
7/10 of maximum frequency