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Mitsubishi Electric MXZ-24UV -E2 Service Manual page 22

Inverter-controlled multi system
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11-3.Heat defrosting control
(1) Conditions to enter defrosting mode
1. When temperature of defrosting thermistor is -3; or less.
2.When specified non-defrosting time is counted in the control P.C. board.
(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 8; or more.
2. When it has spent 10 minutes for defrosting.
Defrosting finishes at condition of 1 or 2.
11-4.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. 49;, the operation frequency is set at the current level.
When temperature of the main pipe temp. thermistor is approx. 52; the protection control decreases the frequency at the
speed of 3Hz a minutes.
When temperature of the main pipe temp. thermistor is approx. 57; 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 45; or less, the protection control is Released.
(2) High pressure protection control by high pressure switch (H.P.S)
High-pressure switch controls the operation frequency and outdoor fan motor.
<Control status>
When high-pressure switch is ON.
(When discharge pipe pressure is 2.75 MPa 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.
<Release status>
When high-pressure switch is OFF. (When discharge pipe pressure is 2.35 MPa or more.)
Or, the compressor stops.
11-5.Discharge temperature protection control
This protection controls the compressor ON/OFF and operation frequency according to temperature of the discharge temp.
thermistor.
(1) Compressor ON/OFF
When temperature of the discharge temp. thermistor exceeds 116;, the control stops the compressor.
When temperature of the discharge temp. thermistor is 80; or less, the controls starts the compressor.
(2) Compressor operation frequency
When temperature of the discharge temp. thermistor is expected to be higher than 116;, the control decreases 12Hz from the
current frequency.
When temperature of the discharge temp. thermistor is expected to be higher than 111; and less than 116;, the control
decreases 6Hz from the current frequency.
When temperature of the discharge temp. thermistor is expected to be higher than 104; and less than 111;, the control is set
at the current frequency.
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