Mitsubishi MSH-GD-VB – E, MU-GD-VB – E, MS-GE-VB – E, MUH-GD-VB – E, MSH-GE-VB – E Service Technical Manual

SERVICE TECHNICAL GUIDE

CONTENTS

1. MSC/MS/MSH MICROPROCESSOR CONTROL · 4

2. MSZ/MLZ MICROPROCESSOR CONTROL ·······11

SPLIT-TYPE AIR CONDITIONERS

No. OBT17

REVISED EDITION-D

Revision D:

•MSC-GE·VB-E, MS-GE·VB-E, MSH­GE·VB-E, MUZ-FD50VA -E, MSZ-GE42/
50VA -

E

and MSZ-CGE42/50VA -E have

been added.

Please void OBT17 REVISED EDITION-C.

CONFIDENTIAL
(FOR INTERNAL USE ONLY)

Models

MSC-GE•VB -

E

MS-GD•VB -

E

· MU-GD•VB -

E

MS-GE•VB -

E

· MU-GE•VB -

E

MSH-GD•VB -

E

· MUH-GD•VB -

E

MSH-GE•VB -

E

· MUH-GE•VB -

E

MSZ-GC•VA -

E

· MUZ-GC•VA(H) -

E

MSZ-HC•VA(B) -

E

· MUZ-HC•VA(B) -

E

MSZ-CHC•VA -

E

MSZ-FD•VA(S) -

E

· MUZ-FD•VA(H)(BH) -

E

MSZ-GE•VA -

E

· MUZ-GE•VA(H) -

E

MSZ-CGE•VA -

E

MLZ-KA•VA -

E

2

Revision A:

• MSZ-FD•VA -

E

has been added.

Revision B:

•MS-GD•VB -E and MSH-GD•VB -E have been added.

Revision C:

• MSZ-FD50VA -

E

, MSZ-GE•VA -E, MSZ-CHC•VA -

E

and MSZ-CGE•VA -E have been added.

Revision D:

• MSC-GE·VB-E, MS-GE·VB-E, MSH-GE·VB-E, MUZ-FD50VA -E, MSZ-GE42/50VA -

E

and MSZ-CGE42/50VA -E

have been added.

3

2. MSZ/MLZ MICROPROCESSOR CONTROL······································································································11

Indoor unit models Outdoor unit models

MSZ-GC22/25/35VA MUZ-GC25/35VA(H)
MSZ-HC25VA MSZ-HC35VA(B) MUZ-HC25VA MUZ-HC35VA(B)
MSZ-CHC25/35VA
MSZ-FD25/35/50VA(S) MUZ-FD25/35VA(H)(BH) MUZ-FD50VABH
MSZ-GE22/25/35/42/50VA MUZ-GE25/35/42/50VA(H)
MSZ-CGE22/25/35/42/50VA
MLZ-KA25/35/50VA

2-1. COOL OPERATION ··································································································································· 11
2-2. DRY OPERATION ······································································································································12
2-3. HEAT OPERATION ····································································································································12
2-4. AUTO CHANGE OVER ··· AUTO MODE OPERATION·············································································15
2-5. OUTDOOR FAN MOTOR CONTROL ········································································································15
2-6. AUTO VANE OPERATION ·························································································································15
2-7. DRAIN PUMP/FLOAT SENSOR CONTROL ·····························································································16
2-8. INVERTER SYSTEM CONTROL ···············································································································17
2-9. OPERATIONAL FREQUENCY CONTROL OF OUTDOOR UNIT ····························································20
2-10. PRE-HEAT CONTROL ·····························································································································21
2-11. EXPANSION VALVE CONTROL/LEV CONTROL ···················································································22

NOTE: As for the multi system type models or MU/MUH-GA type models, refer to the appropriate service technical

guide as well as this service technical guide.

1. MSC/MS/MSH MICROPROCESSOR CONTROL· ·······························································································4

Indoor unit models Outdoor unit models

MSC-GE20VB
MSC-GE25VB
MSC-GE35VB
MS-GD80VB MU-GD80VB
MS-GE50VB MU-GE50VB
MSH-GD80VB MUH-GD80VB
MSH-GE50VB MUH-GE50VB

1-1. COOL OPERATION ·····································································································································4
1-2. DRY OPERATION ········································································································································5
1-3. HEAT OPERATION ······································································································································5
1-4. INDOOR FAN MOTOR CONTROL ··············································································································8
1-5. AUTO VANE OPERATION ···························································································································8
1-6. EXPANSION VALVE CONTROL (LEV CONTROL) ·················································································· 10

4

2. Indoor fan speed control

Indoor fan operates at the set speed by FAN SPEED CONTROL button.

In AUTO the fan speed is as follows.

Initial temperature difference Fan Speed

Room temperature minus set temperature: 1.7°C or more

························································High

Room temperature minus set temperature: between 1 and 1.7°

C ·············································Med.

Room temperature minus set temperature: less than 1°

C ·························································Low

1°C 1.7°C

3°C

3. Coil frost prevention

Temperature control

The coil frost prevention mode in the temperature control is that the indoor fan operates at the set speed and the com-

pressor stops for 5 minutes or more.

Model

Coil frost prevention

ON OFF

Indoor coil thermistor (°C) Indoor coil thermistor (°C)

MSC-GE20VB
MSC-GE25VB

4 °C or less More than 4 °C

MSC-GE35VB 0 °C or less More than 0 °C
MS-GD80VB -1 °C or less More than -1 °C
MS-GE50VB 3 °C or less More than 3 °C
MSH-GD80VB

MSH-GE50VB

1 °C or less More than 1 °C

The coil frost prevention doesn't work for 5 minutes since the compressor has started.

Compressor
Outdoor fan

OFF

ON

(Continuously at set speed)

Indoor fan

ON

ON

OFF

Operation chart
Example

5. Discharge temperature protection (MU-GD80VB, MUH-GD80VB)

The compressor is controlled by the temperature of discharge temperature thermistor for excess rise protection of compres­sor discharge pressure.

• Compressor
When the temperature of discharge temperature thermistor goes to 120°C or more, the compressor is turned OFF. After 3
minutes since the compressor has been turned OFF, if the temperature of discharge temperature thermistor becomes 100
°C or less, the compressor is turned ON.

4. Outdoor fan speed control (MU-GD80VB, MUH-GD80VB)

Outdoor fan speed control is as follows.

Outdoor
fan speed

High
or
Med.

Indoor
fan speed

20°C 22°C

Low

30°C 33°C

High

Temperature of
ambient temperature
thermistor

Low

High
Low

1-1. COOL ( ) OPERATION

1

MSC/MS/MSH MICROPROCESSOR CONTROL

Time control

When the three conditions as follows have been satisfied for 1 hour and 45 minutes, compressor stops for 3 minutes.
a. Compressor has been continuously operating.
b. Indoor fan speed is Low or Med.
c. Room temperature is 26°C or less.
When compressor stops, the accumulated time is cancelled and when compressor restarts, time counting starts from the
beginning.
Time counting also stops temporarily when the indoor fan speed becomes High or the room temperature exceeds 26°C.
However, when two of the above conditions (b. and c.) are satisfied again. Time accumulation is resumed.

-0.3°C

0.3°C

1. Thermostat control (MSC-GE20/25/35VB)
Thermostat is ON or OFF by difference between room temperature and set temperature

Initial temperature difference Thermostat

Room temperature minus set temperature : 0.3°C or more················································ON
Room temperature minus set temperature : less than -0.3°C············································OFF

Set temperature

Difference between room
temperature and set tem­perature during operation

Difference between room
temperature and set tem­perature during operation

5

2. Indoor fan speed control

Indoor fan operates at the set speed by FAN SPEED CONTROL button.
In Auto fan speed becomes Low.

3. The operation of the compressor and indoor/outdoor fan
Compressor operates by room temperature control and time control.
Set temperature is controlled to fall 2°C from initial room temperature.
Indoor fan and outdoor fan operate in the same cycle as the compressor.

● When the room temperature is 23°C or over:
When the thermostat is ON, the compressor repeats 8 minutes ON and 3 minutes OFF.
When the thermostat is OFF, the compressor repeats 4 minutes OFF and 1 minute ON.

● When the room temperature is under 23°C.
When the thermostat is ON, the compressor repeats 2 minutes ON and 3 minutes OFF.
When the thermostat is OFF, the compressor repeats 4 minutes OFF and 1 minute ON.

Set temperature is as shown on the right chart.
The system for dry operation uses the same refrigerant circuit as the
cooling circuit.
The compressor and the indoor fan are controlled by the room tem­perature.
By such controls, indoor flow amounts will be reduced in order to
lower humidity without much room temperature decrease.

DRY operation will not work when the room temperature is 13°C or
below.

1-2. DRY ( ) OPERATION

35

30

25

20

15

10

10 15 20 25 30 35

Set temperature

Initial room temperature

Set temperature and
initial room temperature in DRY mode

Thermostat

Indoor fan

Outdoor fan
Compressor

ON

8 minutes

3

minutes

ON

OFFOFF

OFF

OFF

OFF

OFF

OFF

OFF

ON

ON

ON

ON

ON

ON

Operation time chart
Example
When the room temperature is 23°C or over:

4. Coil frost prevention

• The operation is the same as coil frost prevention during COOL mode.

• The indoor fan operates at the set speed and the compressor does not operate for 5 minutes because the coil frost pre­vention has priority.

1

minute

4

minutes

-0.3°C

0.3°C

1. Thermostat control (MSC-GE20/25/35VB)
Thermostat is ON or OFF by difference between room temperature and set temperature.

Initial temperature difference Thermostat

Room temperature minus set temperature : 0.3°C or more················································ON
Room temperature minus set temperature : less than -0.3°C············································OFF

Set temperature

Difference between room
temperature and set tem­perature during operation

-0.3°C

0.3°C

Set temperature

Difference between room
temperature and set tem­perature during operation

1. Thermostat control (MSC-GE20/25/35VB)
Thermostat is ON or OFF by difference between room temperature and set temperature.

Initial temperature difference Thermostat

Room temperature minus set temperature : less than -0.3°C··············································ON
Room temperature minus set temperature : 0.3°C or more·················································OFF

1-3. HEAT ( ) OPERATION (MSC-GE20/25/35VB, MSH-GD80VB, MSH-GE50VB)

6

(3) Warm air control

When compressor starts in heating operation or after defrosting, the fan changes the speed due to the indoor coil ther­mistor temperature to blow out warm air.
After releasing of cold air prevention, when the indoor coil thermistor temperature is 37°C or above, the fan speed shifts
to the set speed, and when the fan speed is changed by the remote controller, the fan speed is the set speed.
When the indoor coil thermistor temperature is less than 37°C, the fan speed is controlled by time as below.
<Time condition> <Indoor fan speed>
Less than 2 minutes ·······················Low
2 minutes to 4 minutes ···················Med.
4 minutes or more ··························High
The upper limit of the fan speed in MANUAL is the set speed.
The upper limit of the fan speed in AUTO is the speed decided by the indoor fan speed control. (Refer to 1-3.2.(1).)
If the thermostat turns OFF, this operation changes to flow soft control. (MSH-GD80VB, MSH-GE50VB)

(4) Flow soft control (MSH-GD80VB, MSH-GE50VB)

After the thermostat turns OFF, the indoor fan operates at Very Low.
NOTE: When the thermostat turns ON, the fan operates at the set speed. Due to the cold air prevention control, the fan

does not start at set speed until the indoor coil thermistor reads 22°C or more.

3. Outdoor fan speed control (MUH-GD80VB)

Outdoor fan speed control is as follows.

13°C 18°C

Outdoor
fan speed

High

Low

T

emperature of
ambient temperature
thermistor

(2) Cold air prevention control

When the compressor is not operating (MSC-GE20/25/35VB):
( ) If the temperature of indoor coil thermistor RT12 is 0°C or less, the fan stops.
( ) If the temperature of indoor coil thermistor RT12 is more than 0°C, the fan operates at Very Low.

When the compressor is operating:
( ) If the temperature of RT12 is 22°C or more, the fan operates at set speed.
( ) If the temperature of RT12 is less than 22°C and
( ) if the temperature of room temperature thermistor RT11 is 15°C or less, the fan stops.
( ) if the temperature of room temperature thermistor RT11 is more than 15°C, the fan operates at Very Low.

NOTE : If the temperature of RT12 reads from 18°C to 22°C at the air conditioner stating and also after defrosting, this

control works.

Released

Cold Air Prevention

18°C 22°C

Fan speed
Set speed

Very Low or stop

(MSH-GD80VB, MSH-GE50VB) Initial temperature difference Fan speed

Set temperature minus room temperature: 2°C or more ·····················································High
Set temperature minus room temperature: between 1 and 2°C········································· Med.
Set temperature minus room temperature: less than 1°C ····················································Low

1°C 1.7°C

4°C

2°C

2. Indoor fan speed control

(1) In AUTO the fan speed
(MSC-GE20/25/35VB)
Indoor fan speed at set speed by FAN SPEED CONTROL button.

Initial temperature difference Fan speed

Set temperature minus room temperature: 1.7°C or more ·················································High
Set temperature minus room temperature: between 1 and 1.7°

C ·································

Med.

Set temperature minus room temperature: less than 1°

C ·············································

Low

1°C

1.7°C

3°C

Difference between room
temperature and set tem­perature during operation

Difference between room
temperature and set tem­perature during operation

7

4. High pressure protection (MUH-GD80VB, MUH-GE50VB)

During heating operation, the outdoor fan and the compressor are controlled by the temperature of indoor coil thermistor
for excess rise protection of compressor discharge pressure.

• Outdoor fan
When the temperature of indoor coil thermistor goes to 55°C or more, the outdoor fan is turned OFF.
When the temperature of indoor coil thermistor becomes 52°C or less, the outdoor fan is turned ON.

• Compressor
When the temperature of indoor coil thermistor goes to 75°C or more, the compressor is turned OFF.
3 minutes after the compressor is turned OFF and if the temperature of indoor coil thermistor becomes 75°C or less, the

compressor is turned ON.

NOTE: During the high pressure protection and for 10 seconds after high pressure protection, defrosting of outdoor heat

exchanger is not detected by the defrost thermistor.

5. Defrosting

Defrosting of outdoor heat exchanger is controlled by deicer P.C. board, with detection by the defrost thermistor.
(1) Starting conditions of defrost
When all conditions of a) ~ c) are satisfied, the defrosting operation starts.

a) Under the heat operation, the compressor cumulative operation time exceeds 40 minutes without the defrosting opera-

tion working.
b) The defrost thermistor reads -3°C or less.
c) After releasing the high pressure protection 4 minutes and 10 seconds have elapsed.

(2) Releasing conditions of defrost
When the condition d) or e) is satisfied, the defrosting operation stops.

d) The defrost thermistor reads 10°C (MUH-GE50VB) /13°C or more (MUH-GD80VB).
e) The defrosting time exceeds 10 minutes.

(3) Defrosting time chart

Defrost thermistor
13°C or more (MUH-GD80VB)
10°C or more (MUH-GE50VB)

-3°C or less
Outdoor 52C

contactor
(Compressor)

X62
(R.V. coil)

SR61
Outdoor fan

Defrost
counter

Indoor fan

Indoor vane

ON
OFF

ON
OFF

ON
OFF

ON
OFF

ON

OFF
Horizontal

Set position

Maximum 10 minutes

30 seconds

15 seconds

30 seconds

5 seconds

NOTE

Very Low

NOTE: • When the indoor coil thermistor reads above 18°C, indoor fan operates at Very Low for 30 seconds.

• When the indoor coil thermistor reads 18°C or less, the indoor fan stops.

8

1-4. INDOOR FAN MOTOR CONTROL

(1) Rotational frequency feedback control
The indoor fan motor is equipped with a rotational frequency sensor, and outputs signal to the microprocessor to feed-

back the rotational frequency. Comparing the current rotational frequency with the target rotational frequency (High,
Med., Low), the microprocessor controls SR141 and adjusts fan motor electric current to make the current rotational
frequency close to the target rotational frequency. With this control, when the fan speed is switched, the rotational fre­quency changes smoothly.

High

Rotational frequency

High

time

Med.

Low

(2) Fan motor lock-up protection

When the rotational frequency feedback signal has not output for 12 seconds, (or when the microprocessor cannot
detect the signal for 12 seconds) the fan motor is regarded locked-up. Then the electric current to the fan motor is shut­off. 3 minutes later, the electric current is applied to the fan motor again. During the fan motor lock-up, the OPERATION
INDICATOR lamp flashes ON and OFF to show the fan motor abnormality.

1-5. AUTO VANE OPERATION (MSC, MSH)

1. Horizontal vane

(1) Cold air prevention in HEAT operation
When any of the following conditions occur in HEAT operation, the vane angle changes to Angle 1 automatically to pre-

vent cold air blowing on users.
Compressor is not operating.
Defrosting is performed.
Indoor coil thermistor reads 24°C or below.
Indoor coil thermistor temperature is rising from 24°C or below until it reaches 28°C.

NOTE1: If the temperature of the indoor coil thermistor reads from 24 to 28°C at the air conditioner starting, this control

works.

NOTE2: When 2 or more indoor units are operated with multi outdoor unit, even if any indoor unit turns thermostat OFF, this

control doesn’t work in the indoor unit.

Released

Cold Air Prevention

24°C 28°C

Angle 1

Horizontal vane

Set position

Indoor coil thermistor temperature

9

(2) ECONO COOL ( ) operation (ECONOmical operation)
When ECONO COOL button is pressed in COOL mode, set temperature is automatically set 2°C higher.
Also the horizontal vane swings in various cycle according to the temperature of indoor heat exchanger (Tp

( 1)).

SWING operation makes you feel cooler than set temperature. So, even though the set temperature is higher, the air

conditioner can keep comfort. As a result, energy can be saved.

ECONO COOL operation is cancelled when ECONO COOL button, VANE CONTROL button, VANE button or LONG but-

ton is pressed or changed to other operation mode.
NOTE: ECONO COOL operation does not work in COOL mode of “I FEEL CONTROL”.
<SWING operation>
1 Tp: • Value of indoor coil thermistor (MSC-GE20/25/35VB, MS-GE50VB, MSH-GE50VB)

• Average value of indoor coil thermistor (main) and indoor coil thermistor (sub) (MS-GD80VB, MSH-GD80VB)
In swing operation of ECONO COOL operation mode, the initial airflow direction is adjusted to “Horizontal”.

According to the temperature of indoor coil thermistor Tp

( 1) at starting of this operation, next downward blow time is

decided. Then when the downward blow has been finished, next horizontal blow time is decided.
For initial 10 minutes the swing operation is performed in table G~H for quick cooling.
Also, after 10 minutes when the difference between set temperature and room temperature is more than 2°C, the swing

operation is performed in table D ~ H for more cooling.
The air conditioner repeats the swing operation in various cycle as follows.

Temperature of Tp( 1)

Downward blow time

(second)

Horizontal blow time

(second)

A

15°C or less 2 23

B

15 to 17°C 5 20

C

17 to 18°C 8 17

D

18 to 20°C

11 14

E

20 to 21°C 14 11

F

21 to 22°C 17 8

G

22 to 24°C 20 5

H

More than 24°C 23 2

10

NOTE : Opening increases and decreases to be in the target discharge temperature during operation.

Opening
completely

Positioning

Power ON

Initial opening

Standard opening

Remote
controller
ON

Operation

Thermostat
OFF

Standard opening

Thermostat
ON

Opening in stop

Operation

Opening in stop

Remote
controller
OFF

Opening
completely

Remote
controller
ON

Positioning

Standard opening

Operation

Time

LEV opening

Initial opening

Initial opening

Open

Close

(2) LEV time chart

1-6. EXPANSION VALVE CONTROL (LEV CONTROL) (MU-GD80VB, MUH-GD80VB)

LEV (Expansion valve) is controlled by “Thermostat ON” commands given from the unit.

Standard

specification

Control range Minimum: 54 pulse, Maximum: 500 pulse
Drive speed 30 ~ 90 pulse/second

Opening set The setting is always in opening direction.

(To close LEV, it is closed to the pulse smaller than the one set finally.
Then LEV is opened to the final setting pulse.)

General operation

Stop of indoor unit Opening in stop: 150 pulse → LEV opening is set to become 500 pulse after 3 min-

utes.

Remote controller ON LEV positioning (LEV is closed completely at once)
Power ON (Breaker ON) LEV is positioned. However, afterwards, LEV is not positioned when the remote

controller is turned ON for the first time after the power ON.

Approximately for 2 minutes after
compressor has started.

Opening is set by the initial opening.
(Initial opening is set according to each operation mode and outer temperature con­ditions.)

Approximately 2 to 13 minutes (for
11 minutes) after compressor has
started.

Opening is set by standard opening.
(Standard opening is set according to each operation mode and outer temperature
conditions.)

13 minutes after compressor has
started.

LEV opening is corrected once every 2 minutes so that discharge temperature
becomes the target discharge temperature.
(When the discharge temperature is lower than the target temperature: LEV is cor­rected in closed direction, when the discharge temperature is higher than the target
temperature: LEV is corrected in opening direction.)

Thermostat OFF

Opening in stop: 150 pulse → LEV is set to the initial opening after about 3 minutes.

Thermostat ON

Same as the starting of compressor operation

Remote controller OFF

Opening in stop: 150 pulse → LEV is set so that the opening is opened completely
at the speed of 4 pulse every 5 seconds in opening after about 3 minutes.

Operation mode Target discharge temperature (°C)
HEAT (MUH-GD80VB) 85
COOL (Normal) 80
COOL (∆RT is less than 2°C, or ∆RT is 2°C or more and less than 3°C.) 70
COOL (∆RT is 3°C or more.) 65

NOTE: When the discharge temperature is 50°C or less on the cool operation, or is 49°C or less on heat operation

(MUH-GD80VB), LEV opening is set in 54 pulse.
When this state continues for 20 minutes, the compressor is stopped and restarts in 3 minutes.
When the compressor is stopped, the indoor unit indicates the abnormality of refrigerant system and stops.

(OPERATION INDICATOR lamp is 10-time flashing ON and OFF.)

(1) Control data
Reference value of target discharge temperature

11

1. Thermostat control (MSZ)

Thermostat is ON or OFF by difference between room temperature and set temperature.

2-1. COOL ( ) OPERATION

2. Indoor fan speed control

Indoor fan operates continuously at the set speed by FAN SPEED CONTROL button regardless of the thermostat’s OFF­ON. In AUTO, the fan speed is as follows.

3. Coil frost prevention (MSZ)

The compressor operational frequency is controlled to prevent the temperature of indoor heat exchanger from falling exces­sively.
The compressor is turned OFF for 5 minutes when the temperature of indoor coil thermistor continues 3°C or less for 5 min-

utes or more.

The indoor fan maintains the actual speed at the time.

4. Low outside temperature operation (MUZ-GC/FD/GE)
GC25

If the outside temperature falls to 17°C or less during operation in COOL mode, the unit will switch to the low outside
temperature operation mode.
Each outdoor actuator (compressor/fan/LEV) is operated in the exclusive control, which is different from one of normal cool
operation.
Especially, fan motor does not operate continuously to maintain sufficient cooling capacity.
<Operation>
(1) Outdoor fan control
Basically, outdoor unit (compressor) operates with outdoor fan OFF.
But, when any of following conditions are satisfied, the outdoor fan turns ON for about 5 seconds.
a). The defrost thermistor reads 45°C or more.
b). The fin temperature thermistor reads 60°C or more.
(2) LEV (expansion valve) control
In normal cool operation, the opening degree of expansion valve is corrected according to the discharge temperature.
But in this mode it is fixed to the value corresponding to the operation frequency of compressor.
(3) Dew drop prevention
When the ambient temperature thermistor reads -20°C or less, as coil frost or dew drop from indoor unit may occur, the

compressor turns OFF with the outdoor fan ON for prevention of it.
(4) Outdoor temperature detecting control
To detect the exact outdoor temperature in this mode, the compressor turns OFF, but the outdoor fan stays ON for 3

minutes once every 1 hour. If the outdoor temperature rises over 19°C, the unit goes back to the normal COOL mode. If

the outside temperature stays below 19°C, the unit continues to run in the low outside temperature operation mode.

GC35 FD GE

If the outside temperature falls to 18°C or less during operation in COOL mode, the unit will switch to the low outside
temperature operation mode.
<Operation>
(1) Outdoor fan control
The outdoor fan rotation speed slows down to maintain sufficient cooling capacity.

NOTE: Even when the unit is in the "thermostat-off" status under the low outside temperature operation mode, the out-

door fan rotation does not stop.
(2) Dew drop prevention
When the ambient temperature thermistor reads the following temperature, as coil frost or dew drop from indoor unit

may occur, the compressor turns OFF with the outdoor fan OFF for prevention of dew drop.

• -20°C or less (GC35, FD25/35, GE25/35/42)

• -15°C or less (FD50)

• -12°C or less (GE50)
(3) Outdoor temperature detecting control
To detect the exact outdoor temperature in this mode, the compressor turns OFF but the outdoor fan stays ON for 3 min-

utes once evrey 1 hour. If the outdoor temperature rises over about 18°C, the unit goes back to the normal COOL mode.
If the outside temperature stays below about 18°C, the unit continues to run in the low outside temperature operation
mode.

Other protections work as well as in the normal COOL mode.

ON

-1°C or more

Less than -1°C

-1°C

-0.75°C

Room temperature minus
set temperature (During operation)

Room temperature minus
set temperature (Initial)

Thermostat

OFF

High
Med.
Low

1.75°C

3°C

1°C

Fan speed

Room temperature minus
set temperature (During operation)

Room temperature minus
set temperature (Initial)

Between 1 and 1.75°C
Less than 1°C

1.75°C or more

2

MSZ/MLZ MICROPROCESSOR CONTROL

1212

2. Indoor fan speed control

Indoor fan operates at the set speed by FAN SPEED CONTROL button.
When thermostat OFF (compressor OFF), fan speed becomes Very Low.
In AUTO, the fan speed is as follows.

3. Coil frost prevention (MSZ)

Coil frost prevention is as same as COOL mode. (2-1.3.)
The indoor fan maintains the actual speed of the moment. However, when coil frost prevention works while the compressor
is not operating, its speed becomes the set speed.

4. Low outside temperature operation (MUZ-GC/FD/GE)

Low outside temperature operation is as same as COOL mode. (2-1.4.)

NOTE: When 2 or more indoor units are operated with a multi type outdoor unit, the fan operates intermittently at Very Low or

stops in the thermostat-OFF units while at least one unit is thermostat-ON.

High
Med.
Low

1.75°C

2.5°C

1°C

Fan speed

Room temperature minus
set temperature (During operation)

Room temperature minus
set temperature (Initial)

Between 1 and 1.75°C
Less than 1°C

1.75°C or more

2-2. DRY ( ) OPERATION

Set temperature is as shown on the right chart.
The system for dry operation uses the same refrigerant circuit as the
cooling circuit.
The compressor and the indoor fan are controlled by the room tem­perature.
By such controls, indoor air flow amounts will be reduced in order to
lower humidity without much room temperature decrease.

35

30

25

20

15

10

10 15 20 25 30 35

Set temperature (°C)

Initial room temperature (°C)

Set temperature and
initial room temperature in dry mode

1. Thermostat control (MSZ)

Thermostat is ON or OFF by difference between room temperature and set temperature.

ON
OFF

-2°C

-0.75°C

Thermostat

Room temperature minus
set temperature (Initial)

Room temperature minus
set temperature (During operation)

-2

°C or more

Less than -2

°C

2-3. HEAT ( ) OPERATION

1. Thermostat control (MSZ)

Thermostat is ON or OFF by difference between room temperature and set temperature.

ON

2°C or more

Less than 2°C

1.75°C

2°C

Room temperature minus
set temperature (During operation)

Room temperature minus
set temperature (Initial)

Thermostat

OFF

2. Indoor fan speed control

(1) Indoor fan operates at the set speed by F

AN SPEED CONTROL button.

In Auto, the fan speed is as follows.

High
Med.
Low

Fan speed

Room temperature minus
set temperature (During operation)

Room temperature minus
set temperature (Initial)

Between 0.25 and 2°C

Less than 0.25°C

2°C or more

0.25°C

1.75°C

2°C

4°C

1313

(2) Cold air prevention control

When the compressor is not operating,

(

) if the temperature of room temperature thermistor is less than 19°C, the fan stops.

(

) if the temperature of room temperature thermistor is 19°C or more and

(

) if the temperature of indoor coil thermistor is less than 0°C, the fan stops.

(

) if the temperature of indoor coil thermistor is 0°C or more, the fan operates at Very Low.

When the compressor is operating,

(

) if the temperature of indoor coil thermistor is 40°C or more, the fan operates at set speed.

( ) if the temperature of indoor coil thermistor is less than 40°C and

(

) if heating operation starts after defrosting, the fan stops.

(

) if the temperature of room temperature thermistor is 19°C or less, the fan stops.

(

) if the temperature of room temperature thermistor is more than 19°C, the fan operates at Very Low.

NOTE: When 3 minutes have passed since the compressor started operation, this control is released regardless of the

temperature of room temperature thermistor and indoor coil thermistor.

(3) Warm air control (MSZ-FD)

When the following any condition of (a. ~ c.) and the condition of are satisfied at the same time, warm air control
works.

a.) Fan speed is used in MANUAL.
b.) When cold air prevention has been released.
c.) When defrosting has been finished.

When the temperature of indoor coil thermistor is less than 40°C.
When warm air control works, the fan speed changes as follows to blow out warm air gradually.

Gradation of fan speed in initial

<Time condition> <Indoor fan speed>
Less than 2 minutes ------------ Low
2 to 4 minutes -------------------- Med.

More than 4 minutes ----------- High or Super high
The upper limit of the fan speed in MANUAL is the set speed.
When the temperature of indoor coil thermistor has been 40°C or more, or when the set speed has been changed, this
control is released and the fan speed is the set speed.

3. Overload starting

When the room temperature thermistor reads 18°C or more, the compressor runs with its regulated maximum frequency for
a few minutes after the start-up.

4. Defrosting

(1) Starting conditions of defrosting

When the following conditions a) ~ c) are satisfied, the defrosting starts.
a) The defrost thermistor reads: -3°C or less (GC, HC, FD25/35, GE).

-0.6°C or less (FD50).

b) The cumulative operation time of the compressor has reached any of the set values (defrost interval: 40-150 min-

utes).

c) More than 5 minutes have passed since the start-up of the compressor.

The defrost interval is decided by the previous defrosting time. The next defrost interval extends or shortens 0-20

minutes compared with the previous defrost interval.

(2) Releasing conditions of defrosting

Defrosting is released when any of the following conditions are satisfied:
a) The defrost thermistor continues to read following temperature for 30 seconds:

• 5°C or more (GC•VA, HC, FD25/35, GE25/35/42)

• 8°C or more (GC•VAH, FD50)

• 15°C or more (GE50)
b) Defrosting time exceeds 10 minutes.
c) Any other mode than HEAT mode is set during defrosting.

14

Time chart of defrosting in HEAT mode (reverse type)

Set position

Set speed

Set position

Set speed

Indoor fan

Compressor normal

Outdoor fan

R.V. coil

(21S4)

OFF (COOL)

OFF

Maximum frequency

Horizontal

Horizontal vane

Very Low (Temperature of indoor coil thermistor > 18 °C)

30

seconds

30

seconds

30

seconds

40

seconds

5 seconds 5 seconds

40

seconds

OFF

OFF

OFF

ON (HEAT)

ON ON

ON (HEAT)

Compressor normal

<FD50>

Reverse defrost frequency

30

seconds

30

seconds

30

seconds

5 seconds 5 seconds

30

seconds

OFF

OFF

Horizontal (Temperature of indoor coil thermistor 39 °C

)

<Indoor unit>

<Outdoor unit>

30

seconds

14

5. Defrost heater (GC·VAH, FD·VAH/VABH, GE·VAH)

(1) Starting conditions

When all of the following conditions a) ~ d) are satisfied, defrost heater turns ON to prevent ice from foaming on the
base of outdoor unit.
a) HEAT mode is selected.
b) The ambient temperature thermistor reads 5°C or less for 5 minutes continuously. (NOTE1).
c) The defrost thermistor reads -1°C or less for 5 minutes continuously.
d) Outdoor fan motor is turned ON.

(2) Releasing conditions

When any of the following conditions are satisfied, defrost heater turns OFF.
a) Any other mode than HEAT mode is selected. (NOTE2).
b) The ambient temperature thermistor reads 8°C or more for 5 minutes continuously. (NOTE1).
c) The defrost thermistor reads more than 15°C for 5 minutes continuously.
d) Outdoor fan motor is turned OFF.

NOTE1: Ambient temperature thermistor

NOTE2: During defrosting operation, defrost heater continues to be ON.

Defrost heater
ON
OFF

5°C 8°C

1515

2-4. AUTO CHANGE OVER ··· AUTO MODE OPERATION (MSZ-GC/FD/GE/CGE, MLZ-KA)

Once desired temperature is set, unit operation is switched automatically between COOL and HEAT operation.

1. Mode selection

(1) Initial mode

At first, indoor unit operates only indoor fan with outdoor unit OFF for 3 minutes to detect present room temperature.

Following the conditions below, operation mode is selected.

If the room temperature thermistor reads higher than set temperature, COOL mode is selected.
If the room temperature thermistor reads set temperature or lower, HEAT mode is selected.

(2) Mode change

In case of the following conditions, the operation mode is changed.

COOL mode changes to HEAT mode when 15 minutes have passed with the room temperature 1 - 2°C below the set

temperature.

HEAT mode changes to COOL mode when 15 minutes have passed with the room temperature 1 - 2°C above the set

temperature.

In the other cases than the above conditions, the present operation mode is continued.

NOTE1: Mode selection is performed when multi standby (refer to NOTE2) is released and the unit starts operation with

ON timer.

NOTE2: If two or more indoor units are operating in multi system, there might be a case that the indoor unit, which is

operating in AUTO ( ), cannot change over the other operating mode (COOL ↔ HEAT) and becomes a state
of standby.

(3) Indoor fan control/Vane control

As the indoor fan speed and the horizontal vane position depend on the selected operation mode, when the operation
mode changes over, they change to the exclusive ones.

2-5. OUTDOOR FAN MOTOR CONTROL

Fan speed is switched according to the compressor frequency.

2-6. AUTO VANE OPERATION

1. Horizontal vane

(1) Cold air prevention in HEAT operation

When any of the following conditions occur in HEAT operation, the vane angle changes to horizontal position automati-

cally to prevent cold air blowing directly onto users.

Compressor is not operating.
Defrosting is performed.
Temperature of indoor coil thermistor does not exceed following temperature within about 3 minutes after compressor

starts.

• 24°C (MSZ)

• 18°C (MLZ)

NOTE: When 2 or more indoor units are operated with multi outdoor unit, even if any indoor unit turns thermostat OFF,

this control doesn’t work in the indoor unit.

(2) ECONO COOL (

) operation (ECONOmical operation)
When ECONO COOL button is pressed in COOL mode, set temperature is automatically set 2°C higher.
Also the horizontal vane swings in various cycle according to the temperature of indoor coil thermistor.
SWING operation makes you feel cooler than set temperature. So, even though the set temperature is higher, the air
conditioner can keep comfort. As a result, energy can be saved.
ECONO COOL operation is cancelled when ECONO COOL button is pressed once again or VANE CONTROL button is
pressed or change to other operation mode.

Compressor frequency (Hz)

Down Up

MUZ-HC/GC

41 54

MUZ-FD25/35
MUZ-GE35/42

33 43

MUZ-FD50

25 33

MUZ-GE25

41 54

MUZ-GE50

33 44

High

Low

Down Up

Fan speed

Minimum Compressor frequency Maximum

1616

<SWING operation>
In swing operation of ECONO COOL operation mode, the initial air flow direction is adjusted to “Horizontal”.
According to the temperature of indoor coil thermistor at starting of this operation, next downward blow time is decided.
After the downward blow has been finished, next horizontal blow time is decided.
For initial 10 minutes, the swing operation is performed in table G ~ H for quick cooling.
Also, after 10 minutes when the difference of set temperature and room temperature is more than 2°C, the swing opera­tion is performed in table D ~ H for more cooling.
The air conditioner repeats the swing operation in various cycle as follows.

Temperature of indoor coil

thermistor (°C)

Downward blow time

(second)

Horizontal blow time

(second)
A 15 or less 2 23
B 15 to 17 5 20
C 17 to 18 8 17
D

18 to 20

11 14
E 20 to 21 14 11
F 21 to 22 17 8

G 22 to 24 20 5

H More than 24 23 2

2-7. DRAIN PUMP/FLOAT SENSOR CONTROL (MLZ)

Drain pump motor OFF

When ON timer is set, or during multi system operation.

Operation mode

Start

Judge water level

COOL/DRY

Above fi xed point

Outdoor unit STOP

Rejudge water level

Indoor unit STOP

Above fi xed point

Abnormal indication

Below fi xed point

Below fi xed point

Drain pump motor ON

Above fi xed point

Judge water level

Below fi xed point

2 minutes later

Judge water level

Above fi xed point

HEAT/STAND-BY /STOP

Drain pump motor ON

Below fi xed point

17

Function of main parts

NAME FUNCTION
INTELLIGENT POWER MODULE (IPM) It supplies three-phase AC power to compressor.
SMOOTHING CAPACITOR It stabilizes the DC voltage and supply it to IPM.
CURRENT TRANSFORMER It measures the current of the compressor motor.
DIODE MODULE 1 It converts the AC voltage to DC voltage.

RESISTOR

It absorbs the rush current not to run into the main power supply circuit
when the electricity turns ON.

RELAY

It short-circuits the resistance which restricts rush current during the nor­mal operation after the compressor startup.

BOOSTER
CHOPPER
CIRCUIT

DIODE MODULE 2

It improves power factor.
It controls the bus-bar voltage.

SWITCHING POWER TRANSISTOR
REACTOR

2-8. INVERTER SYSTEM CONTROL

2-8-1. Inverter main power supply circuit

MUZ-GC, HC, FD25/35, GE

POWER
SUPPLY

NOISE
FILTER
CIRCUIT

RESISTOR

SWITCHING
POWER
TRANSISTOR

RELAY

SMOOTHING
CAPACITOR

CURRENT
TRANSFORMER

COMPRESSOR

DIODE
MODULE1

DIODE
MODULE2

REACTOR

P

W

V

U

N

IPM

U

W

MS

3~

V

+

BOOSTER CHOPPER CIRCUIT

+

-

~~

+

-

~~

POWER
SUPPLY

NOISE
FILTER
CIRCUIT

RESISTOR

RELAY

SMOOTHING
CAPACITOR

CURRENT
TRANSFORMER

COMPRESSOR

REACTOR

P

W

V

U

N

IPM

PFC

U

W

MS

3~

V

+

MUZ-FD50

Function of main parts

NAME FUNCTION
INTELLIGENT POWER MODULE (IPM) It supplies 3-phase AC power to compressor.
SMOOTHING CAPACITOR It stabilizes the DC voltage and supplies it to IPM.

CURRENT TRANSFORMER

It measures the current of the compressor motor.
It measures the current of the main power supply circuit.

REACTOR

It rectifi es AC, controls its voltage and improves the power factor of power
supply.

POWER FACTOR CORRECTION MODULE (PFC)
RESISTOR It restricts rush current with the resistance.

RELAY

It short-circuits the resistance which restricts rush current during the compres­sor operates.

18

Input current waveform without PAM Input current waveform with PAM

Due to the time of no electricity;

• Power factor gets worse.

• Harmonic gets increased.
Input voltage

Energized time is short in
case L inductance is small.

No electricity runs into
diode module because the
voltage at both sides of smoothing
capacitor is higher than input voltage.

Input current

Owing to the increase of energized time;

• Power factor gets better.

• Harmonic gets suppressed.

Release of energy stored in L.

Peak gets down.

Energized time is
extended by
optimization
of L inductance.

Compulsory energizing
by switching.

2-8-2. Outline of main power supply circuit
MUZ-GC, HC, FD25/35, GE

1. At the start of operation

Main power supply circuit is formed when RELAY is turned ON at COMPRESSOR startup.
To prevent rush current from running into the circuit when power supply is turned ON, RESISTOR is placed in sub circuit.

2. At normal operation

When AC runs into P.C. board, its external noise is eliminated in the NOISE FILTER CIRCUIT.
After noise is eliminated from AC, it is rectifi ed to DC by DIODE MODULE 1.
DC voltage, to which AC has been rectifi ed by process , is stabilized by SMOOTHING CAPACITOR and supplied to IPM.
DC voltage, which has been stabilized in process , is converted to three-phase AC by IPM and supplied to COMPRES-

SOR.

3. Purpose of PAM adoption

PAM: Pulse Amplitude Modulation
PAM has been adopted for the effi ciency improvement and the adaptation to IEC harmonic current emission standard.

Outline of simple partial switching method

In conventional inverter models, DIODE MODULE rectifi es AC voltage to DC voltage, SMOOTHING CAPACITOR makes its DC
waveform smooth, and IPM converts its DC voltage to imitate AC voltage again in order to drive the compressor motor.
However, it has been diffi cult to meet IEC harmonic current emission standard by above circuit because harmonic gets gener-
ated in the input current waveform and power factor gets down. The simple partial switching method with PAM, which has been
adopted this time, places and utilizes BOOSTER CHOPPER CIRCUIT before rectifying AC voltage in the general passive-meth­od converter circuit. As harmonic gets suppressed and the peak of waveform gets lower by adding BOOSTER CHOPPER CIR­CUIT as mentioned above and by synchronizing the timing of switching with the zero-cross point of waveform, the input current
waveform can be improved and the requirement of IEC harmonic current emission standard can be satisfi ed. Since the switching
is synchronized with the zero cross point, this simple partial switching method has the feature of lower energy loss compared to
active fi lter method. In addition, output and effi ciency is enhanced by combining with vector-controlled inverter in order to boost
the voltage of power supplied to IPM.

4. Intelligent power module

IPM consists of the following components

• IGBT (x6) : Converts DC waveform to 3-phase AC waveform and outputs it.

• Drive Circuit : Drives transistors.

• Protection circuit : Protects transistors from overcurrent.
Since the above components are all integrated in IPM, IPM has a merit to make the control circuit simplify and miniaturize.

5. Elimination of electrical noise

NOISE FILTER CIRCUIT, which is formed by *CMC COILS capacitors placed on P.C. board, eliminates electrical noise of AC
power that is supplied to main power supply circuit. And this circuit prevents the electrical noise generated in the inverter cir­cuit from leaking out.

*CMC COILS: Common mode choke coils

19

MUZ-FD50

1. At the start of operation

Main power supply circuit is formed when RELAY is turned ON at COMPRESSOR startup.
To prevent rush current from running into the circuit when power supply is turned ON, RESISTOR are placed in sub circuit.

2. At normal operation

When AC runs into noise fi lter P.C. board, its external noise is eliminated in NOISE FILTER CIRCUIT.
After noise being eliminated from AC, it is rectifi ed to DC by REACTOR and PFC. If the operating frequency becomes 25

Hz or more, DC voltage rises to 370 V.

DC voltage, to which has AC been rectifi ed by process

, is stabilized by SMOOTHING CAPACITOR and supplied to IPM.

The DC (Bus voltage), which has been stabilized in process , is converted to 3 phase AC by IPM and supplied to COM-

PRESSOR.

CURRENT TRANSFORMER which is placed in the power supply circuit to COMPRESSOR, is used to measure the value

of phase current and locates the polar direction of rotor with algorithm. PWM (Pulse width modulation) controls impressed
voltage and frequency with those information.

3. Power factor improvement

Booster coil reactor and power factor controller rectify AC to DC and control its voltage.
In the motor drive system of sine wave control, power factor can be improved by reducing harmonics. PFC and reactor that
stabilizes the voltage of DC supplied to inverter circuit and makes its waveform smooth.

4. Power transistor module

IPM consists of the following components.

• Power Transistors (x6) : Converts DC waveform to 3-phase AC waveform and outputs it.

• Drive Circuit : Drives transistors.

• Protection circuit : Protects transistors from over current.
Since the above components are all integrated in IPM, IPM has a merit that can get the control circuit simplifi ed and miniatur-
ized.

5. Elimination of electrical noise

NOISE FILTER CIRCUIT, which is formed by *CMC COILS and capacitors placed on the noise fi lter P.C. board, eliminates
electrical noise of AC power that is supplied to main power supply circuit. In short, common mode noise is absorbed in this
circuit.
Moreover, normal mode noise is absorbed in another NOISE FILTER CIRCUIT which is formed by *NMC COILS and capaci­tors.
Both NOISE FILTER CIRCUITS exist for preventing the electrical noise generated in the inverter circuit from leaking out.

*CMC COILS: Common mode choke coils
*NMC COILS: Normal mode choke coils

2-8-3. Sine wave control

In these air conditioners, compressor equips brushless DC motor which does not have hall element.
In short, the motor is sensorless. However, it is necessary to locate the polar direction of rotor in order to drive brushless DC
motor effi ciently. The general detection method of the polar direction for such a DC motor is to locate it from the induced voltage
by unenergized stator.
Therefore, it is necessary to have a certain period of time in which the stator is being unenergized for the rotor position detection
when the supplied power voltage is impressed.
So the motor has been driven by square wave control (the conventional motor drive system) which energizes the motor only
when the range of electrical angle is within 120° because it is forced to be unenergized within 30° at start and end of one heap
in one waveform cycle (180°) when the voltage is impressed.
However, torque pulsation occurs at rotation in this method when the current-carrying phases are switched over to other phases
in sequence. Therefore, sine wave control system is adopted for these air conditioners because it can make the phase-to-phase
current waveform smoother (sine wave) in order to drive the motor more effi ciently and smoothly.

2-8-4. Characteristics of sine wave control in case of brushless DC motor

● Although ordinary three-phase induction motor requires energy to excite the magnetic fi eld of rotor, brushless DC motor does
not need it. So, higher effi ciency and torque are provided.

● This control provides the most effi cient waveform corresponding to the rotation times of compressor motor.

● The rotation can be set to higher compared to the conventional motor drive system. So, the time in which air conditioner can

be operated with saved energy is longer than conventional models. This can save annual electric consumption.

● Compared to square wave control, the torque pulsation is reduced at rotation so that the motor operates more quietly.

● Since response and effi ciency of motor are enhanced in sine wave control, fi ner adjustment can be provided.

DC Motor AC Motor
Rotor Permanent magnet is embedded Excited by magnetic fi eld of stator
Rotor Position Signal Necessary Unnecessary

In brushless DC motor, permanent magnet is embedded in the rotor. Therefore, it does not require energy to excite the

rotor like AC motor does. However, it is necessary to control the frequency of three-phase AC current supplied to the sta­tor according to the polar direction of magnet embedded in the rotor so as to drive the motor effi ciently. Controlling three-
phase AC current frequency also means controlling the timing to switch the polarity of stator. Therefore, the polar direction
of rotor needs to be detected.

2020

2-8-5. Control Method of Rotation Times

Sine wave control makes the current transformers conduct real time detection of the value of the current running into the mo­tor, locates the rotor position from the detected value, and decides if voltage should be impressed and if frequency should be
changed.
Compared to the conventional control and rotor position detection method, sine wave control can provide fi ner adjustment of the
voltage of supplied power. The value of the current running into the motor is determined by each motor characteristic.

2-9. OPERATIONAL FREQUENCY CONTROL OF OUTDOOR UNIT

1. Outline
The operational frequency is as follows:
First, the target operational frequency is set based on the difference between the room temperature and the set tem­perature.
Second, the target operational frequency is regulated by discharge temperature protection, high pressure protection,
electric current protection, overload protection, and the maximum/minimum frequency.

2. Maximum/minimum frequency in each operation mode

Applied model

Operational frequency (Hz)

COOL HEAT DRY

Minimum Maximum Minimum Maximum Minimum Maximum

MUZ-GC25 32 85 28 105 32 41
MUZ-GC35 32 98 48 105 32 58
MUZ-HC25 28 85 28 105 28 41
MUZ-HC35 28 98 28 98 28 41
MUZ-FD25 10 52 18 90 28 41
MUZ-FD35VA 10 62 18 90 28 41
MUZ-FD35VAH/VABH 10 62 18 115 28 41
MUZ-FD50 20 85 20 130 20

45

MUZ-GE25 24 93 32 105 38

48

MUZ-GE35 20 98 32 98 38

55

MUZ-GE42 10 90 18 115 35

54

MUZ-GE50 20 98 20 108 20

98

The operation frequency in COOL mode is restricted by the upper limit frequency after 0.5 - 1 hour as shown

below for dew prevention. It is rated frequency or less.

Maximum
frequency

0.5 - 1 hour

Upper limit
frequency

Rated frequency or less

Time

2121

2-10. PRE-HEAT CONTROL

MUZ-GC, HC, FD, GE

1. Outline
Compressor is energized to improve the start-up of compressor at a low outside temperature even when compressor

is stopped.

2. Pre-heat control

Pre-heat control ON condition

(1) Compressor is not operating. (However, pre-heat control is still OFF for 30 minutes after compressor is stopped,

regardless of the outside temperature.)
(2) Outside temperature is 20°C or below.
Outside temperature is monitored hourly, and when outside temperature is 20°C or below, pre-heat control is turned

ON.
When pre-heat control is turned ON, compressor is energized about 50 W (40-60 W). (Compressor and fan are not

operated.)

30 minutes 1 hour

ON

ON

OFF

OFF

20 °C

Compressor

Pre-heat control

Outside temperature

2. Pre-heat control ON condition
(1) Pre-heat control is turned ON for 15 or 30 min

after the breaker is turned ON.

(2) 30 min. after the unit is stopped, pre-heat control is turned ON for 15 or 30 min.

and turned OFF for 30 min.

This is repeated as shown in the graph until the breaker is turned OFF.

When outside temperature is 20°C or below, pre-heat control is ON for 30 min.

When outside temperature is 21°C or above, pre-heat control is ON for 15 min.
NOTE: When the unit is started with the remote controller, pre-heat control is turned OFF.

Compressor uses 50 W when pre-heat control is turned ON.

1. Outline
The compressor is energized even while it is not operating.
This is to generate heat at the winding to improve the compressor's start-up condition.

Power ON

OFF

Compressor ON

OFF

Outside temperature

30min.

30min. 30min. 30min. 30min. 30min. 15min. 30min. 15min. 30min.

Pre-heat ON

OFF

Breaker ON

20°C

Stop
operation

Start
operation

When outside
temperature is
above 20°C

22

2-11. EXPANSION VALVE CONTROL/LEV CONTROL (MUZ-GC/FD/GE HC35)

(1) Outline of LEV control
The LEV basic control is setting of LEV opening degree to the standard opening degrees set for each operational fre­quency of the compressor. However, when any change in indoor/outdoor temperatures or other factors cause air condi­tioning load fluctuation, the LEV control also works to correct LEV opening degree based on discharge temperature (Shell
temperature) of the compressor, developing the unit’s performance.

Standard

specification

Control range

Minimum : 54 pulse
Maximum : 500 pulse

Actuating speed

Open: 40 pulse/second
Close: 90 pulse/second.

Opening degree adjustment LEV opening degree is always adjusted in opening direction.

(When reducing the opening degree, LEV is once over-closed,
and then adjusted to the proper degree by opening.

General operation

Unit OFF LEV remains at maximum opening degree. (LEV is reached

maximum opening degree approximate in 15 minutes after
compressor stops)

Remote controller ON LEV is positioned. (First LEV is full closed at zero pulse and

then positioned.)

During 1 to 15 minutes after compressor starts LEV is fixed to standard opening degree according to opera-

tional frequency of compressor.
More than about 15 minutes have passed since com­pressor start-up

LEV opening degree is corrected to get target discharge tem-

perature of compressor.

(For lower discharge temperature than target temperature,

LEV is corrected in closing direction.)

(For higher discharge temperature than target temperature,

LEV is corrected in opening direction.)

It may take more than 30 minutes to reach target tempera-

ture, depending on operating conditions.
Thermostat OFF LEV is adjusted to exclusive opening degree for thermostat

OFF.
Thermostat ON LEV is controlled in the same way as that after the compressor

has started up.
Defrosting in HEAT mode LEV is adjusted to open 500 pulse.

22

(2) Time chart

OFF Time

Time

ON

Operational frequency

of the compressor

Commanded
to open

Standard
opening
degree

Opening degree is
corrected according
to discharge
temperature.
(Refer to (3))

Positioning

Air conditioner ON

Air conditioner OFF
(thermostat off)

LEV opening degree

About 15 minutes

2323

In COOL operation, the two indoor coil
thermistors (one main and one sub) sense
temperature ununiformity (super heat)
at the heat exchanger, and when tem­perature difference have developed, the
indoor coil thermistors adjust LEV open­ing degree to get approximate 10°C lower
temperature than the target discharge
temperature in the table on the left, thus
diminishing super heat.

(3) Control data

Reference value of target discharge temperature (COOL/HEAT °C)

Applied model

ABCDEF

MUZ-GC25 54/36 59/46 65/55 70/63 75/70 79/76
MUZ-GC35 51/42 57/50 62/58 67/65 71/70 71/70

MUZ-FD25/35
MUZ-GE42

49/43 55/51 61/59 67/69 72/75 76/80

MUZ-FD50 45/51 58/59 65/65 72/72 72/72 72/72
MUZ-GE25 52/43 58/50 65/55 67/59 70/65 71/69
MUZ-GE35 53/43 60/51 64/58 67/59 72/69 76/75
MUZ-GE50 57/60 60/65 62/70 67/75 74/75 81/75

F
E
D
C
B

A

Target discharge

temperature

30 50 70

Operational frequency of the compressor (Hz

)

90 110 130

HEAD OFFICE: TOKYO BLDG.,2-7-3, MARUNOUCHI, CHIYODA-KU, TOKYO 100-8310, JAPAN

New publication, effective Dec. 2008
Specifications subject to change without notice.

© Copyright 2007 MITSUBISHI ELECTRIC CO.,LTD

Distributed in Dec. 2008. No. OBT17 REVISED EDITION-D 6
Distributed in Aug. 2008. No. OBT17 REVISED EDITION-C 5
Distributed in Apr. 2008. No. OBT17 REVISED EDITION-B 7
Distributed in Aug. 2007. No. OBT17 REVISED EDITION-A 7
Distributed in Feb. 2007. No. OBT17 7
Made in Japan