Discharge Temperature Protection Control; Refrigerant Recovery Control On Heating; Outdoor Fan Control; Compressor Operation Frequency - Mitsubishi Electric MSH09TW Service Manual

<Release status>
When high-pressure switch is OFF. (When discharge pipe pressure is 340.8 PSIG or more.)
Or, the compressor stops.

10-16. 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 240.8°F, the control stops the compressor.
When temperature of the discharge temp. thermistor is 212°F or less, the controls starts the compressor.

(2) Compressor operation frequency

When temperature of the discharge temp. thermistor is expected to be higher than 240.8°F, the control decreases 12Hz from
the current frequency.
When temperature of the discharge temp. thermistor is expected to be higher than 231.8°F and less than 240.8°F, the con-
trol decreases 6Hz from the current frequency.
When temperature of the discharge temp. thermistor is expected to be higher than 219.2°F and less than 231.8°F, the con-
trol is set at the current frequency.

10-17. Refrigerant recovery control on heating

<Control status>
The control performs when the all following status are satisfied;
• When there is 1 unit or more not operating indoor unit on heat operation. (Excluding thermo OFF)
• When discharge temperature becomes 224.6°F or more.
• When it passed 60 minutes or more since the operation has started or the last refrigerant recovery has controlled.
<Control details>
LEV opening, which adjusts to not operating indoor unit, is considered to be 80 pulse.
<Control finish status>
The control finishes either as follows. However, the LEV opening is considered to be 59 pulse.
• When it passed 60 seconds since the control has started.
• When the discharge temperature is 194°F or less.

10-18. Outdoor fan control

Fan speed is switched according to a number of operating indoor unit and the compressor frequency.
Fan speed
Down
Hi
Low
Min. Compressor frequency
<Relation between compressor frequency and fan speed.>
Mode
Fan speed
COOL
HEAT
Note
• When operation, fan speed of High/ Low mode changes to Very High/ High mode by promoting those fan speeds respec-
tively by 1 step after defrosting is operated. This control is cleared, when the compressor off.
• When overheat protection of P.C. board temperature or fin temperature operates, the outdoor fan speed is fixed to Very High
mode regardless of compressor frequency. Also, when the overheat protection is cleared, the fan speed is back to normal
• When the indoor coil thermistor is 134.6°F or more on HEAT operation, fan speed is fixed to Low notch .
Or, the indoor coil thermistor is 113°F or less on HEAT operation, fan speed is back to normal.
Up
Max.
Indoor unit operation
Single Double
Up 55 Hz 50Hz
Down 45 Hz 45 Hz
Up 60 Hz 45 Hz
Down 50 Hz 40 Hz
Triple
50 Hz
45 Hz
40 Hz
35 Hz
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