Mitsubishi Electronics Mitsubishi Digital Electronics Air Conditioner Muz Fdna U User Manual

Revision B:  
MXZ-2A20NA- 1 , MXZ-4A36NA, MSZ-FD,  
MSZ-D and MSY-D have been added.  
Please void OBT16 REVISED EDITION-A.  
No. OBT16  
REVISED EDITION-B  
SERVICE TECHNICAL GUIDE  
Wireless type Models  
MS-A•WA  
MSZ-A•NA  
· MU-A•WA  
· MUZ-A•NA  
· MUZ-A•NA -  
· MUY-A•NA  
U
MSY-A•NA  
MSZ-FD•NA · MUZ-FD•NA  
U
· MUZ-FD•NA -  
· MUZ-D•NA  
MSZ-D•NA  
MSY-D•NA  
U
· MUZ-D•NA -  
· MUY-D•NA  
Inverter-controlled multi system type Models  
· MXZ-A•NA  
CONTENTS  
1. MS MICROPROCESSOR CONTROL··················4  
2. MSZ, MSY MICROPROCESSOR CONTROL······7  
3. MXZ MICROPROCESSOR CONTROL··············21  
1. MS MICROPROCESSOR CONTROL···························································4  
Indoor unit models  
Outdoor unit models  
MS-A09WA  
MS-A12WA  
MU-A09WA  
MU-A12WA  
1-1. COOL OPERATION ···············································································4  
1-2. DRY OPERATION ··················································································4  
1-3. AUTO VANE OPERATION·····································································6  
2. MSZ, MSY MICROPROCESSOR CONTROL···············································7  
Indoor unit models  
Outdoor unit models  
MSZ-A09NA  
MSZ-A12NA  
MSZ-A15NA  
MSZ-A17NA  
MSZ-A24NA  
MSY-A15NA  
MSY-A17NA  
MSY-A24NA  
MSZ-FD09NA MUZ-A09NA  
MSZ-FD12NA MUZ-A12NA  
MUZ-FD09NA  
MUZ-FD12NA  
MUZ-D30NA  
MUZ-D36NA  
MUY-D30NA  
MUY-D36NA  
MSZ-D30NA  
MSZ-D36NA  
MSY-D30NA  
MSY-D36NA  
MUZ-A15NA  
MUZ-A17NA  
MUZ-A24NA  
MUY-A15NA  
MUY-A17NA  
MUY-A24NA  
2-1. COOL OPERATION ··············································································7  
2-2. DRY OPERATION ·················································································8  
2-3. HEAT OPERATION···············································································8  
2-4. AUTO CHANGE OVER ··· AUTO MODE OPERATION ·····················10  
2-5. OUTDOOR FAN MOTOR CONTROL·················································11  
2-6. AUTO VANE OPERATION··································································11  
2-7  
2-8  
2-9  
.
.
.
INVERTER SYSTEM CONTROL························································12  
OPERATIONAL FREQUENCY CONTROL OF OUTDOOR UNIT ·····17  
EXPANSION VALVE CONTROL (LEV CONTROL)···························18  
3. MXZ MICROPROCESSOR CONTROL·······················································21  
Outdoor unit models  
MXZ-2A20NA  
MXZ-3A30NA  
MXZ-4A36NA  
3-1. INVERTER SYSTEM CONTROL·························································21  
3-2. EXPANSION VALVE CONTROL (LEV CONTROL)····························23  
3-3. OPERATIONAL FREQUENCY RANGE ··············································29  
3-4. HEAT DEFROSTING CONTROL·························································30  
3-5. DISCHARGE TEMPERATURE PROTECTION CONTROL·······················30  
3-6. OUTDOOR FAN CONTROL ································································30  
3-7. PRE-HEAT CONTROL·········································································31  
3-8. COOL OPERATION····················································································31  
3-9. DRY OPERATION·································································· BACK COVER  
3-10  
. HEAT OPERATION···························································BACK COVER  
3
1
MS MICROPROCESSOR CONTROL  
MS-A•WA  
MU-A•WA  
1-1. COOL ( ) OPERATION  
1. Thermostat control  
Thermostat is ON or OFF by difference between room temperature and set temperature  
Room temperature minus  
Room temperature minus  
set temperature (Initial)  
set temperature (During operation)  
Thermostat  
ON  
OFF  
-1.8 °F or more  
less than-1.8 °F  
-1.8 °F  
-1.3 °F  
2. Indoor fan speed control  
Indoor fan operates continuously at the set speed by FAN SPEED CONTROL button regardless of the thermostat’s OFF-  
ON.  
In AUTO the fan speed is as follows.  
Room temperature minus  
set temperature (Initial)  
3.1 °F or more  
Room temperature minus  
set temperature (During operation)  
Fan speed  
High  
Med.  
Low  
between 1.8 and 3.1 °F  
less than 1.8 °F  
5.4 °F  
3.1 °F  
1.8 °F  
3. Coil frost prevention  
Temperature control  
When the indoor coil thermistor RT12 reads 37 °F or below the coil frost prevention mode starts immediately.  
However, the coil frost prevention doesn’t work for 5 minutes since the compressor has started.  
The indoor fan operates at the set speed and the compressor stops for 5 minutes.  
After that, if the indoor coil thermistor still reads below 37 °F, this mode is prolonged until the indoor coil thermistor reads  
over 37 °F.  
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 below 79 °F.  
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 79 °F.  
However, when two of the above conditions (b. and c.) are satisfied again. Time accumulation is resumed.  
Operation chart  
Example  
ON  
Compressor  
Outdoor fan  
OFF  
( Continuously at set speed)  
Indoor fan  
ON  
Set temperature and  
initial room temperature in dry mode  
1-2. DRY ( ) OPERATION  
°F  
95  
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 tem-  
perature.  
By such controls, indoor flow amounts will be reduced in order to  
lower humidity without much room temperature decrease.  
86  
77  
68  
59  
50  
50  
59  
68  
77  
86  
95 °F  
Initial room temperature  
4
1. Thermostat control  
Thermostat is ON or OFF by difference between room temperature and set temperature.  
Room temperature minus  
Room temperature minus  
set temperature (Initial)  
set temperature (During operation)  
Thermostat  
ON  
OFF  
-1.8 °F or more  
less than-1.8 °F  
-1.8 °F  
-1.3 °F  
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.  
Room temperature minus  
set temperature (Initial)  
3.1 F or more  
Room temperature minus  
set temperature (During operation)  
Fan speed  
High  
Med.  
Low  
between 1.8 and 3.1 F  
less than 1.8 F  
4.5  
F
3.1  
F
1.8  
F
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 4 °F from initial room temperature.  
Indoor fan and outdoor fan operate in the same cycle as the compressor.  
•When the room temperature is 73 °F 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 73 °F.  
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.  
Operation time chart  
Example  
ON  
Thermostat  
OFF  
ON  
Indoor fan  
OFF  
ON  
Outdoor fan  
Compressor  
OFF  
8 minutes  
4 minutes  
3 minutes  
1 minute  
4. Coil frost prevention  
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.  
5
1-3. AUTO VANE OPERATION  
1. Horizontal vane  
ECONO COOL (  
) operation (ECONOmical operation)  
When ECONO COOL button is pressed in COOL mode, set temperature is automatically set 3.6 °F higher than that in  
COOL mode.  
Also the horizontal vane swings in various cycle according to the temperature of indoor heat exchanger (indoor coil  
thermistor).  
SWING operation makes you feel cooler than set temperature. So, even though the set temperature is higher than that  
in COOL mode, 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.  
<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.  
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 of set temperature and room temperature is more than 3.6 °F, 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 (°F)  
Downward blow time Horizontal blow time  
(second)  
(second)  
A
B
C
D
E
F
59 or less  
59 to 63  
63 to 64  
64 to 68  
68 to 70  
70 to 72  
72 to 75  
more than 75  
2
5
8
11  
14  
17  
20  
23  
23  
20  
17  
14  
11  
8
G
H
5
2
6
2
MSZ,MSY MICROPROCESSOR CONTROL  
MSZ-A•NA  
MSY-A•NA  
MUZ-A•NA  
MUY-A•NA  
MSZ-FD•NA MSY-D•NA  
MSZ-D•NA  
MUZ-FD•NA MUY-D•NA  
MUZ-D•NA  
2-1. COOL ( ) OPERATION  
1. Thermostat control  
Thermostat is ON or OFF by difference between room temperature and set temperature  
Room temperature minus  
set temperature (Initial)  
Room temperature minus  
set temperature (During operation)  
Thermostat  
ON  
OFF  
-1.8 °F or more  
less than-1.8 °F  
-1.8 °F  
-1.3 °F  
2. Indoor fan speed control  
Indoor fan operates continuously at the set speed by FAN SPEED CONTROL button regardless of the thermostat’s OFF-  
ON.  
In AUTO the fan speed is as follows.  
Room temperature minus  
set temperature (Initial)  
3.1 °F or more  
Room temperature minus  
set temperature (During operation)  
MSZ-A  
MSY-A  
Fan speed  
High  
Med.  
Low  
between 1.8 and 3.1 °F  
less than 1.8 °F  
5.4 °F  
3.1 °F  
1.8 °F  
Room temperature minus  
set temperature (Initial)  
2.7 °F or more  
between 1.8 and 2.7 °F  
less than 1.8 °F  
Room temperature minus  
set temperature (During operation)  
MSZ-FD  
MSZ-D  
MSY-D  
Fan speed  
High  
Med.  
Low  
5.4 °F  
2.7 °F  
1.8 °F  
3. Coil frost prevention  
The compressor operational frequency is controlled to prevent the temperature of indoor heat exchanger from falling exces-  
sively.  
The compressor is turned OFF for 5 minutes when the temperature of indoor coil thermistor continues 37 °F or less for 5  
minutes or more.  
The indoor fan maintains the actual speed of the moment.  
4. Low outside temperature operation  
If the outside temperature falls to 64 °F or less during operation in COOL mode, the unit will switch to the low outside tem-  
perature 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 10 °F (MUZ-A MUY-A MUZ-D MUY-D), -4 °F (MUZ-FD) 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  
them.  
(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  
minutes once 1 hour. If the outdoor temperature rises over 64 °F, the unit goes back to the normal COOL mode. If the  
outside temperature stays below 64 °F, the unit continues to run in the low outside temperature operation mode.  
Other protections work as well as in the normal COOL mode.  
7
Set temperature and  
initial room temperature in dry mode  
2-2. DRY ( ) OPERATION  
°F  
95  
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 tem-  
perature.  
By such controls, indoor flow amounts will be reduced in order to  
lower humidity without much room temperature decrease.  
86  
77  
68  
59  
50  
50  
59  
68  
77  
86  
95 °F  
Initial room temperature  
1. Thermostat control  
Thermostat is ON or OFF by difference between room temperature and set temperature.  
Room temperature minus  
set temperature (Initial)  
Room temperature minus  
set temperature (During operation)  
Thermostat  
ON  
OFF  
-1.8 °F or more  
less than-1.8 °F  
-1.8 °F  
-1.3 °F  
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.  
Room temperature minus  
set temperature (Initial)  
3.1 F or more  
Room temperature minus  
set temperature (During operation)  
Fan speed  
High  
Med.  
Low  
between 1.8 and 3.1 F  
less than 1.8 F  
4.5  
F
3.1  
F
1.8  
F
3. Coil frost prevention  
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  
Low outside temperature operation is as same as COOL mode. (2-1.4.)  
2-3. HEAT ( ) OPERATION (MSZ)  
1. Thermostat control  
Thermostat is ON or OFF by difference between room temperature and set temperature.  
Room temperature minus  
set temperature (Initial)  
less than 3.6 °F  
Room temperature minus  
set temperature (During operation)  
Thermostat  
ON  
OFF  
3.6 °F or more  
3.6 °F  
3 °F  
2. Indoor fan speed control  
(1) Indoor fan operates at the set speed by FAN SPEED CONTROL button.  
In Auto the fan speed is as follows.  
Room temperature minus  
set temperature (Initial)  
Room temperature minus  
set temperature (During operation)  
Fan speed  
High  
Med.  
Low  
3.6 °F or more  
between 0.4 and 3.6 °F  
less than 0.4 °F  
3.6 °F 7.2 °F  
0.4 °F  
3 °F  
8
(2) Cold air prevention control  
MSZ-A09/12/15/17 MSZ-FD MSZ-D  
When the compressor is not operating,  
( ) if the temperature of room temperature thermistor is less than 66 °F, the fan stops.  
(
) if the temperature of room temperature thermistor is 66 °F or more and  
( ) if the temperature of indoor coil themistor is less than 32 °F, the fan stops.  
(
) if the temperature of indoor coil themistor is 32 °F or more, the fan operates at Very Low.  
When the compressor is operating,  
( ) if the temperature of indoor coil themistor is 104 °F or more, the fan operates at set speed.  
(
) if the temperature of indoor coil themistor is less than 104 °F and  
( ) if heating operation starts after defrosting, the fan stops.  
(
(
) if the temperature of room temperature thermistor is 66 °F or less, the fan stops.  
) if the temperature of room temperature thermistor is more than 66 °F, 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.  
MSZ-A24  
When the compressor is not operating,  
( ) if the temperature of room temperature thermistor is 59 °F or less, or temperature of indoor coil thermistor is  
less than 64 °F, the fan stops.  
(
) if the temperature of room temperature thermistor is more than 59 °F, or temperature of indoor coil themistor is  
more than 64 °F, the fan operates at Very Low.  
When the compressor is operating,  
( ) if the temperature of indoor coil themistor is 64 °F or more, the fan operates at set speed.  
(
) if the temperature of indoor coil themistor is less than 64 °F and  
( ) if heating operation starts after defrosting, the fan stops.  
(
(
) if the temperature of room temperature thermistor is 59 °F or less, the fan stops.  
) if the temperature of room temperature thermistor is more than 59 °F, 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 104 °F.  
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 minutes 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 104 °F 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 64 °F or more, the compressor runs with its maximum frequency regulated for  
10 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 27 °F or less.  
b) The cumulative operation time of the compressor has reached any of the set values (40, 45, 55, 65, 75, 85, 95, 105,  
115, 125, 150 minutes.  
c) More than 5 minutes have passed since the start-up of the compressor.  
Set value of compressor operation time (here in after referred to as defrost interval)  
This is decided by the temperature of defrost thermistor, ambient temperature thermistor, and the previous defrosting  
time. For example, the first defrost interval is 40 minutes long, and the second is 45 minutes long. The third and sub-  
sequent intervals are set to be longer, and less frequent, depending on defrosting time.  
The third and subsequent defrost intervals follow any of the three patterns 5 or 10 to 20 minutes longer, the same,  
or 5 or 10 to 20 minutes shorter compared with the previous defrost interval  
shortest 40 minutes.  
with the longest 125 minutes and the  
9
(2) Releasing conditions of defrosting  
Defrosting is released when any of the following conditions is satisfied:  
a) The defrost thermistor continues to read 50 °F or more (MUZ-A09/12 MUZ-D) / 41 °F or more (MUZ-A15/17 MUZ-FD) /  
59 °F or more (MUZ-A24) for 30 seconds.  
b) Defrosting time has exceeded 10 minutes.  
c) Any other mode than HEAT mode is set during defrosting.  
Time chart of defrosting in HEAT mode (reverse type)  
<Indoor unit>  
horizontal  
set position  
set speed  
set position  
set speed  
Horizontal vane  
Indoor fan  
<
horizontal (temperature of indoor coil thermistor 102 °F)  
Very Low (temperature of indoor coil thermistor > 64 °F)  
OFF  
30  
seconds  
<Outdoor unit>  
Maximum frequency  
Compressor normal  
OFF  
30  
OFF  
30  
40  
40  
seconds seconds  
seconds seconds  
5 seconds  
5 seconds  
ON  
ON  
Outdoor fan  
OFF  
ON (HEAT)  
ON (HEAT)  
R.V. coil  
(21S4)  
OFF (COOL)  
2-4. AUTO CHANGE OVER ··· AUTO MODE OPERATION (MSZ)  
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 more than set temperature, COOL mode is selected.  
If the room temperature thermistor reads set temperature or less, HEAT mode is selected.  
10  
(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 4 °F below the set  
temperature.  
HEAT mode changes to COOL mode when 15 minutes have passed with the room temperature 4 °F 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 (  
of standby.  
), cannot change over the other operating mode (COOL  
HEAT) and becomes a state  
(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.  
<Relation between compressor frequency and fan speed>  
Compressor frequency (Hz)  
Fan speed  
High  
Down  
Up  
Down  
Up  
MUZ-A  
MUY-A  
33  
44  
Low  
Min. Compressor frequency Max.  
MUZ-FD  
33  
39  
44  
54  
MUZ-D  
MUY-D  
2-6. AUTO VANE OPERATION  
1. Horizontal vane  
(1) Cold air prevention in HEAT operation (MUZ)  
When any of the following conditions occurs in HEAT operation, the vane angle changes to Horizontal position automati-  
cally to prevent cold air blowing on users.  
Compressor is not operating.  
Defrosting is performed.  
Indoor coil thermistor temperature does not exceed 102 °F within about 3 minutes after compressor starts.  
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 3.6 °F higher than that in  
COOL mode.  
Also the horizontal vane swings in various cycle according to the temperature of indoor heat exchanger (indoor coil  
thermistor).  
SWING operation makes you feel cooler than set temperature. So, even though the set temperature is higher than that  
in COOL mode, 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.  
11  
<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 RT12 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 of set temperature and room temperature is more than 3.6 °F, 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 (°F)  
Downward blow time Horizontal blow time  
(second)  
(second)  
A
B
C
D
E
F
59 or less  
59 to 63  
63 to 64  
64 to 68  
68 to 70  
70 to 72  
72 to 75  
more than 75  
2
5
8
11  
14  
17  
20  
23  
23  
20  
17  
14  
11  
8
G
H
5
2
2-7. INVERTER SYSTEM CONTROL  
2-7-1. Inverter main power supply circuit  
MUZ-A09/12/15/17  
MUY-A15/17  
MUZ-FD  
CURRENT  
DIODE  
TRANSFORMER  
REACTOR  
MODULE1  
U
U
V
P
NOISE  
FILTER  
CIRCUIT  
RESISTOR  
RELAY  
+
+
POWER  
SUPPLY  
~
~
SMOOTHING  
CAPACITOR  
MS  
3~  
V
-
N
W
W
IPM  
COMPRESSOR  
+
~
~
SWITCHING  
POWER  
TRANSISTOR  
DIODE  
MODULE2  
-
BOOSTER CHOPPER CIRCUIT  
Function of main parts  
NAME  
FUNCTION  
INTELLIGENT POWER MODULE (IPM)  
SMOOTHING CAPACITOR  
CURRENT TRANSFORMER  
DIODE MODULE 1  
It supplies three-phase AC power to compressor.  
It stabilizes the DC voltage and supply it to IPM.  
It measures the current of the compressor motor.  
It converts the AC voltage to DC voltage.  
It absorbs the rush current not to run into the main power supply circuit when  
the electricity turns ON.  
RESISTOR  
RELAY  
It short-circuits the resistance which restricts rush current during the normal  
operation after the compressor startup.  
DIODE MODULE 2  
BOOSTER  
It improves power factor.  
It controls the bus-bar voltage.  
SWITCHING POWER TRANSISTOR  
CHOPPER  
CIRCUIT  
REACTOR  
12  
MUZ-A24  
MUY-A24  
MUZ-D  
MUY-D  
CURRENT  
TRANSFORMER  
REACTOR  
U
U
V
P
N
NOISE  
FILTER  
CIRCUIT  
RESISTOR  
RELAY  
+
POWER  
SUPPLY  
SMOOTHING  
CAPACITOR  
MS  
3~  
PFC  
V
W
W
IPM  
COMPRESSOR  
Function of main parts  
NAME  
FUNCTION  
INTELLIGENT POWER MODULE (IPM)  
SMOOTHING CAPACITOR  
It supplies three-phase AC power to compressor.  
It stabilizes the DC voltage and supplies it to IPM.  
It measures the current of the compressor motor.  
It measures the current of the main power supply circuit.  
CURRENT TRANSFORMER  
REACTOR  
It recties AC, controls its voltage and improves the power factor of power  
supply.  
POWER FACTOR CORRECTION MODULE (PFC)  
RESISTOR  
RELAY  
It restricts rush current with the resistance.  
It short-circuits the resistance which restricts rush current during the compres-  
sor operates.  
13  
2-7-2. Outline of main power supply circuit  
MUZ-A09/12/15/17 MUY-A15/17 MUZ-FD  
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 POWER P.C. board, its external noise is eliminated in NOISE FILTER CIRCUIT.  
After noise is eliminated from AC, it is rectied to DC by DIODE MODULE 1.  
DC voltage, to which AC has been rectied 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.  
CURRENT TRANSFORMER, which is placed in the power supply circuit to COMPRESSOR, are used to measure the val-  
ue of phase current and locate the polar direction of rotor with algorithm. PWM (Pulse width modulation) controls impressed  
voltage and frequency with those information.  
3. Purpose of PAM adoption  
PAM : Pulse Amplitude Modulation  
PAM has been adopted for the efciency improvement and the adaptation to IEC harmonic current emission standard  
Outline of simple partial switching method  
In conventional inverter models, DIODE MODULE recties AC voltage to DC voltage, SMOOTHING CAPACITOR makes its  
DC waveform smooth, and IPM converts its DC voltage to imitated AC voltage again in order to drive the compressor motor.  
However, it has been difficult to meet IEC harmonic current emission standard by above circuit because harmonic gets  
generated 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 satised.  
Since the switching synchronized with the zero cross point, this simple partial switching method has the feature of lower en-  
ergy loss compared to active lter method. In addition, output and efciency is enhanced by combining with vector-controlled  
inverter in order to boost the voltage of power supplied to IPM.  
Input current waveform without PAM  
Input current waveform with PAM  
Due to the time of no electricity;  
· Power factor gets worse.  
· Harmonic gets increased.  
Owing to the increase of energized time;  
· Power factor gets better.  
· Harmonic gets suppressed.  
Input current  
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.  
14  
4. Intelligent power module  
IPM consists of the following components  
· IGBT (x6)  
: Converts DC waveform to three-phase AC waveform and outputs it.  
· Drive Circuit  
· Protection circuit  
: Drives transistors.  
: 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 the POWER P.C. board, eliminates electri-  
cal 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  
MUZ-A24 MUY-A24 MUZ-D MUY-D  
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 filter P.C. board, its external noise is eliminated in NOISE FILTER CIRCUIT.  
After noise being eliminated from AC, it is rectified 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 rectified by process , is stabilized by SMOOTHING CAPACITOR and supplied to IPM.  
The DC (Bus voltage), which has been stabilized in process , is converted to three-phase AC by IPM and supplied to  
COMPRESSOR.  
CURRENT TRANSFORMER, which is placed in the power supply circuit to COMPRESSOR, are used to measure the  
value of phase current and locate the polar direction of rotor with algorithm. PWM (Pulse width modulation) controls im-  
pressed 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 stabi-  
lize the voltage of DC supplied to inverter circuit and make its waveform smooth.  
4. Power transistor module  
IPM consists of the following components.  
· Power Transistors (x6) : Converts DC waveform to three-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 simplified and miniatur-  
ized.  
5. Elimination of electrical noise  
NOISE FILTER CIRCUIT, which is formed by *CMC COILS and capacitors placed on the noise filter 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 capaci-  
tors.  
Both NOISE FILTER CIRCUIT exists 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  
15  
2-7-3. Sine wave control  
In these air conditioners, compressor equips brushless DC motor which doesn't have Hall element.  
In short, the motor is sensorless. However, it's necessary to locate the polar direction of rotor in order to drive brushless DC mo-  
tor efciently. The general detection method of the polar direction for such a DC motor is to locate it from the voltage induced 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 voltage of supplied power 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 & 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 efciently and smoothly.  
2-7-4. Characteristics of sine wave control in case of brushless DC motor  
Although ordinary three-phase induction motor requires energy to excite the magnetic eld of rotor, brushless DC motor  
doesn't need it. So, higher efciency and torque are provided.  
This control provides the most efcient 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 energy saved 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 efciency of motor are enhanced in sine wave control, ner adjustment can be provided.  
DC Motor  
Permanent magnet is embedded  
Necessary  
AC Motor  
Excited by magnetic eld of stator  
Unnecessary  
Rotor  
Rotor Position Signal  
In brushless DC motor, permanent magnet is embedded in the rotor. Therefore, it doesn't require energy to excite the rotor  
like AC motor does. However, it's necessary to control the frequency of three-phase AC current supplied to the stator accord-  
ing to the polar direction of magnet embedded in the rotor so as to drive the motor efciently. Controlling 3 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.  
2-7-5. 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 mo-  
tor, 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 ner adjustment of the  
voltage of supplied power. The value of the current running into the motor is determined by each motor characteristic.  
16  
2-8. OPERATIONAL FREQUENCY CONTROL OF OUTDOOR UNIT  
1. Outline  
The operational frequency is as following:  
First, the target operational frequency is set based on the difference between the room temperature and the set tem-  
perature.  
Second, the target operational frequency is regulated by discharge temperature protection, high pressure protection,  
electric current protection and overload protection and also by the maximum/minimum frequency.  
2. Maximum/minimum frequency in each operation mode.  
Unit: Hz  
COOL  
HEAT (MUZ)  
DRY  
Applied model  
Minimum Maximum Minimum Maximum Minimum Maximum  
frequency frequency frequency frequency frequency frequency  
MUZ-A09  
MUZ-A12  
32  
32  
70  
73  
32  
32  
76  
71  
32  
32  
57  
57  
MUZ-A15  
MUY-A15  
MUZ-A17  
MUY-A17  
MUZ-A24  
MUY-A24  
10  
10  
15  
82  
87  
15  
15  
15  
93  
93  
10  
10  
15  
68  
68  
110  
108  
102  
MUZ-FD09  
MUZ-FD12  
MUZ-D30  
MUY-D36  
MUZ-D36  
MUY-D36  
10  
10  
20  
20  
20  
20  
52  
62  
84  
79  
91  
92  
10  
10  
20  
20  
100  
100  
87  
10  
10  
20  
20  
20  
20  
41  
41  
83  
79  
83  
79  
94  
The operation frequency in COOL mode is restricted by the upper limit frequency after 1 hour or 0.5 ~ 1 hour as  
shown below for dew prevention.  
It is rated frequency or less.  
Maximum  
frequency  
Upper limit  
1 hour  
frequency  
or  
Rated frequency or less  
Time  
0.5~1 hour  
17  
2-9. EXPANSION VALVE CONTROL (LEV CONTROL)  
(1) Outline of LEV control  
The LEV basic control is comprised of setting LEV opening degree to the standard opening °F set for each operational  
frequency of the compressor. However, when any change in indoor/outdoor temperatures or other factors cause air con-  
ditioning 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.  
Minimum  
: 33 pulse (MUZ-A09/12/15/17 MUY-A15/17)  
59 pulse (MUZ-A24 MUY-A24)  
54 pulse (MUZ-FD)  
Control range  
58 pulse (MUZ-D MUY-D)  
: 500 pulse  
Maximum  
Open : 40 pulse/second  
Close : 90 pulse/second.  
Actuating speed  
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.  
Unit OFF  
LEV remains at maximum opening degree (reaches maximum  
opening degree approximate in 15 minutes after compressor  
stops)  
Remote controller ON  
LEV is positioned. (first full-closed at zero pulse and then posi-  
tioned.)  
COOL · DRY MODE  
During 1 to 5 minutes after compressor starts  
LEV is fixed to standard opening degree according to opera-  
tional frequency of compressor.  
HEAT MODE  
During 1 to 15 minutes after compressor starts  
More than 5 (COOL, DRY), 15 (HEAT (MUZ)) minutes LEV opening degree is corrected to get target discharge tem-  
have passed since compressor start-up  
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  
Thermostat ON  
LEV is adjusted to exclusive opening degree for thermostat  
OFF.  
LEV is controlled in the same way as that after the compres-  
sor has started up.  
Defrosting in HEAT mode  
LEV is adjusted to open 500 pulse.  
18  
(2) Time chart  
Air conditioner OFF  
(thermostat off)  
Air conditioner ON  
Positioning  
Opening degree is  
corrected according  
to discharge  
Standard  
opening  
degree  
Commanded  
to open  
temperature.  
about 5 minutes <COOL, DRY>  
about 15 minutes <HEAT>  
Time  
ON  
OFF Time  
(3) Control data  
06  
05  
F
E
D
04  
03  
02  
01  
C
B
A(target discharge temperature)  
(Hz)  
30  
50  
70  
90  
110  
130  
Operational frequency of the compressor  
(a) Reference value of target discharge temperature  
(COOL / HEAT (MUZ) F)  
Applied model  
A
B
C
D
E
F
COOL  
HEAT  
COOL  
HEAT  
COOL  
HEAT  
COOL  
HEAT  
COOL  
HEAT  
122  
113  
129  
120  
140  
140  
120  
109  
126  
131  
127  
126  
136  
136  
140  
145  
131  
124  
135  
140  
140  
138  
147  
151  
140  
149  
142  
138  
149  
149  
151  
154  
158  
165  
145  
153  
153  
156  
167  
154  
158  
169  
158  
180  
147  
158  
162  
167  
183  
162  
158  
169  
158  
185  
153  
158  
169  
176  
187  
167  
MUZ-A09/12  
MUZ-A15/17  
MUY-A15/17  
MUZ-A24  
MUY-A24  
MUZ-FD  
MUZ-D  
MUY-D  
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 degrees lower temperature than the target temperature in the table  
above, thus diminishing super heat.  
19  
(b) Reference value of LEV standard opening degree (pulse)  
Applied model  
A
B
C
D
E
F
COOL  
HEAT  
COOL  
HEAT  
COOL  
HEAT  
COOL  
HEAT  
COOL  
HEAT  
130  
100  
290  
130  
150  
130  
180  
130  
150  
100  
190  
130  
300  
150  
166  
150  
240  
180  
170  
120  
240  
170  
350  
220  
186  
170  
300  
240  
210  
140  
260  
210  
350  
250  
206  
196  
320  
270  
250  
190  
260  
230  
370  
280  
230  
210  
320  
300  
280  
240  
260  
230  
370  
300  
260  
226  
320  
300  
300  
280  
MUZ-A09/12  
MUZ-A15/17  
MUY-A15/17  
MUZ-A24  
MUY-A24  
MUZ-FD  
MUZ-D  
MUY-D  
20  
3
MXZ MICROPROCESSOR CONTROL  
MXZ-A•NA  
3-1. INVERTER SYSTEM CONTROL  
3-1-1. Inverter main power supply circuit  
CURRENT  
TRANSFORMER  
REACTOR  
U
U
V
P
N
NOISE  
FILTER  
CIRCUIT  
RESISTOR  
RELAY  
+
POWER  
SUPPLY  
SMOOTHING  
CAPACITOR  
MS  
3~  
PFC  
V
W
W
IPM  
COMPRESSOR  
Function of main parts  
NAME  
FUNCTION  
INTELLIGENT POWER MODULE (IPM)  
SMOOTHING CAPACITOR  
It supplies three-phase AC power to compressor.  
It stabilizes the DC voltage and supplies it to IPM.  
It measures the current of the compressor motor.  
CURRENT TRANSFORMER  
It measures the current of the main power supply circuit.  
REACTOR  
It recties AC, controls its voltage and improves the power factor of power  
supply.  
POWER FACTOR CORRECTION MODULE (PFC)  
RESISTOR  
RELAY  
It restricts rush current with the resistance.  
It short-circuits the resistance which restricts rush current during the compres-  
sor operates.  
3-1-2. Outline of main power supply circuit  
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 lter P.C. board, its external noise is eliminated in NOISE FILTER CIRCUIT.  
After noise being eliminated from AC, it is rectied 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 rectied by process , is stabilized by SMOOTHING CAPACITOR and supplied to IPM.  
The DC (Bus voltage), which has been stabilized in process , is converted to three-phase AC by IPM and supplied to  
COMPRESSOR.  
CURRENT TRANSFORMER, which is placed in the power supply circuit to COMPRESSOR, are used to measure the val-  
ue of phase current and locate the polar direction of rotor with algorithm. PWM (Pulse width modulation) controls impressed  
voltage and frequency with those information.  
21  
3. Power factor improvement  
Booster coil reactor and PFC 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 stabi-  
lize the voltage of DC supplied to inverter circuit and make its waveform smooth.  
4. Power transistor module  
IPM consists of the following components.  
· Power Transistors (x6) : Converts DC waveform to three-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 simplied and miniatur-  
ized.  
5. Elimination of electrical noise  
NOISE FILTER CIRCUIT, which is formed by *CMC COILS and capacitors placed on the noise 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 capaci-  
tors.  
Both NOISE FILTER CIRCUIT exists 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  
3-1-3. Sine wave control  
In these air conditioners, compressor equips brushless DC motor which doesn't have Hall element.  
In short, the motor is sensorless. However, it's necessary to locate the polar direction of rotor in order to drive brushless DC mo-  
tor efciently. The general detection method of the polar direction for such a DC motor is to locate it from the voltage induced 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 voltage of supplied power 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 & 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 efciently and smoothly.  
3-1-4. Characteristics of sine wave control in case of brushless DC motor  
Although ordinary three-phase induction motor requires energy to excite the magnetic eld of rotor, brushless DC motor  
doesn't need it. So, higher efciency and torque are provided.  
This control provides the most efcient 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 energy saved 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 efciency are enhanced in sine wave control, ner adjustment can be provided.  
DC Motor  
Permanent magnet is embedded  
Necessary  
AC Motor  
Excited by magnetic eld of stator  
Unnecessary  
Rotor  
Rotor Position Signal  
In brushless DC motor, permanent magnet is embedded in the rotor. Therefore, it doesn't require energy to excite the rotor  
like AC motor does. However, it's necessary to control the frequency of three-phase AC current supplied to the stator accord-  
ing to the polar direction of magnet embedded in the rotor so as to drive the motor efciently. Controlling 3 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.  
3-1-5. 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 mo-  
tor, 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 ner adjustment of the  
voltage of supplied power. The value of the current running into the motor is determined by each motor characteristic.  
22  
3-2. EXPANSION VALVE CONTROL (LEV CONTROL)  
Linear expansion valve (LEV) is controlled by “Thermostat ON” commands given from each unit.  
Indoor unit status  
LEV opening  
Stop of all indoor unit  
Opening before stop 500 pulse in 15 minutes  
When outdoor unit is operating, COOL : 5 pulse (full closed)  
some indoor units stop and some HEAT :(MXZ-2A / 3A30NA) : 140 pulse (slightly opened)  
1
:(MXZ-3A30NA-  
/ 4A ) : 100 59 pulse  
operate.  
When the outdoor unit operates (When the other indoor unit operates) : 5 pulse.  
When outdoor unit stops. (When the other indoor unit stops or thermo off) :  
Maintain LEV opening before stop 500 pulse in 15 minutes  
Thermostat OFF in COOL or DRY  
mode  
• LEV opening for each indoor unit is determined by adding adjustment in accordance  
with the number of operating unit and the capacity class to standard opening, based  
on the operation frequency:  
Ex.) Opening 130 pulse in standard opening 1 Minimum 80 pulse, Maximum 205  
pulse. (Capacity code 4 at 1 unit operation) (Capacity code 1 at 3 units operation)  
Thermostat ON in COOL or DRY • After starting operation, adjustment in accordance with intake super heat, discharge  
mode  
temperature is included in standard opening. 1  
NOTE: LEV opening in each frequency at DRY operation and COOL operation is the  
same. However, velocity and compressor operation frequency controls are differ-  
ent. See 3-3. OPERATIONAL FREQUENCY RANGE  
(As far as the indoor unit velocity control goes, refer to DRY operation in MICRO-  
PROCESSOR CONTROL in indoor unit.)  
• When the outdoor unit operates. (When the other indoor unit operates) : 140 pulse.  
Thermostat OFF in HEAT mode • When the outdoor unit stops. (When the other indoor unit stops or thermo off) : Main-  
tain LEV opening before stop 500 pulse in 15 minutes. “  
• LEV opening for each indoor unit is determined by adding adjustment in accordance  
with the number of operating unit and the capacity class to standard opening, based  
on the operation frequency:  
Ex.) Opening 120 pulse in standard opening 1 Minimum 70 pulse, Maximum 165  
pulse. (Capacity code 4 at 1 unit operation) (Capacity code 1 at 3 units operation)  
• After starting operation, opening becomes the one that adjustment in accordance with  
discharge temperature was added to basic opening. 1 “  
Thermostat ON in HEAT mode  
1 LEV opening when the outdoor unit is operating: Upper limit 500 pulse, Lower limit 53pulse (MXZ-2A / 3A30NA), 59 pulse  
1
(MXZ-3A30NA-  
/ 4A).  
23  
MXZ-2A20NA/3A30NA  
The table below shows the role of Exclusive LEV and Receiver LEV in each operation mode.  
Discharge  
Capacity Distribution Temperature  
Protection  
Evaporation  
Temperature  
Protection  
Circulation Amount  
Control  
High Pressure  
Protection  
Exclusive LEV  
Receiver LEV  
Exclusive LEV  
Receiver LEV  
×
×
×
×
COOL  
HEAT  
Outdoor  
heat  
Indoor heat Exclusive  
exchanger LEV  
exchanger  
Receiver  
Receiver  
LEV  
(MXZ-3A30NA)  
In COOL mode, 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 to dimin-  
ish the super heat. This action is called Evaporation Temperature Protection.  
The opening pulse of the Receiver LEV is fixed to the standard No.3 in cooling operation, and so is that of each Exclusive  
LEV in heating operation.  
However the opening pulse will be changed to the standard No.4 or No.5 when the discharge temperature protection or high-  
pressure protection is working.  
In addition to that, it will also be changed to standard No.2 or No.1 when the opening pulse of the each Exclusive LEV  
becomes 100 pulse or less in cooling operation or so does that of Receiver LEV in heating operation.  
<MXZ-2A20NA>  
Number of  
operating  
indoor units  
LEV opening (pulse)  
COOL  
HEAT  
Standard No.  
1 unit  
200  
300  
400  
450  
500  
2 units  
1 unit  
120  
140  
160  
220  
280  
2 units  
120  
140  
160  
220  
1
2
3
4
5
150  
320  
360  
410  
500  
280  
<MXZ-3A30NA>  
Number of  
operating  
indoor units  
LEV opening (pulse)  
COOL  
HEAT  
1 unit  
2 units  
250  
320  
360  
410  
3 units  
1 unit  
2 units  
250  
300  
380  
400  
3 units  
Standard No.  
1
2
3
4
5
150  
250  
350  
400  
450  
250  
320  
370  
420  
470  
250  
300  
450  
460  
470  
250  
300  
380  
390  
440  
460  
450  
24  
Determination of LEV standard opening in each indoor unit  
• The standard opening is on the straight line, which connects an each standard point in the section where divided into  
seven according to the operation frequency of compressor as shown in the figure below.  
(LEV opening is controlled in proportion to the operation frequency.)  
NOTE: Opening is adjusted at the standard opening according to the indoor unit conditions.  
However, inclination of standard opening in each point of opening does not change with the original curve.  
• Add opening provided in Difference in capacity in the table below to the standard opening from 1 to 8, when capacity  
of the indoor unit is excluding code 1.  
• Add opening provided in Difference in operation number in the table below to determined LEV opening for each  
indoor unit, when 2 or 3 indoor units are operated at the same time.  
NOTE: Even when the adjusted standard opening exceeds the driving range from 59 to 500 pulse, actual driving out-  
put opening is in a range from 59 to 500 pulse.  
4Hz  
10  
09  
08  
07  
06  
05  
04  
03  
02  
01  
23 38 54 69 84 100 115 131 146 MXZ-2A  
14 23 32 41 50 59 68 77 86 MXZ-3A/4A  
Compressor operating frequency (Hz)  
MXZ-2A20NA  
Standard opening (pulse)  
LEV Opening (code)  
COOL  
1
2
3
4
5
6
7
8
9
10  
120 130 136 146 156 160 170 180 190 200  
100 110 120 130 146 160 170 180 190 200  
HEAT  
Difference in capacity  
Difference in operation number  
Code3,4 Code5,6 Code7,8 Code9,10 Code11,12 Code13,14 Code15or above  
2
-20  
0
COOL  
HEAT  
3
3
6
6
9
9
12  
52  
15  
55  
25  
65  
35  
75  
MXZ-3A30NA  
Standard opening (pulse)  
LEV Opening (code)  
COOL  
1
2
3
4
5
6
7
8
9
10  
126 130 134 138 140 142 182 228 296 310  
140 146 150 170 180 200 224 244 272 280  
HEAT  
Difference in capacity  
Difference in operation number  
Code3,4 Code5,6 Code7,8 Code9,10 Code11,12 Code13,14 Code15or above  
2
-20  
0
3
-30  
0
COOL  
HEAT  
3
3
6
6
9
9
12  
52  
15  
55  
25  
65  
35  
75  
25  
1
MXZ-2A20NA-  
Exclusive LEV  
Standard opening (pulse)  
LEV Opening (code)  
COOL  
1
2
3
4
5
6
7
8
9
10  
120 130 136 146 156 160 170 180 190 200  
248 248 258 266 274 280 286 292 300 306  
HEAT  
Difference in capacity  
Difference in operation number  
Code3,4 Code5,6 Code7,8 Code9,10 Code11,12 Code13,14 Code15or above  
2
COOL  
HEAT  
3
3
6
6
9
9
12  
52  
15  
55  
25  
65  
35  
75  
-20  
30  
Receiver LEV  
Standard opening (pulse)  
LEV Opening (code)  
COOL  
1
2
3
4
5
6
7
8
9
10  
140 150 160 170 180 190 200 200 200 200  
80 84 90 110 120 130 140 150 160 170  
HEAT  
Difference in operation number  
Operation number  
2
COOL  
HEAT  
-20  
30  
1
MXZ-3A30NA-  
MXZ-4A36NA  
Exclusive LEV  
Standard opening (pulse)  
LEV Opening (code)  
COOL  
1
2
3
4
5
6
7
8
9
10  
126 130 134 138 150 160 170 180 190 200  
248 248 258 266 274 280 286 292 300 306  
HEAT  
Difference in capacity  
Difference in operation number  
Code3,4 Code5,6 Code7,8 Code9,10 Code11,12 Code13,14 Code15or above  
2
-20  
-4  
3
-30  
-8  
4(MXZ-4A)  
-30  
-12  
COOL  
HEAT  
3
3
6
6
9
9
12  
52  
15  
55  
25  
65  
35  
75  
Receiver LEV  
Standard opening (pulse)  
LEV Opening (code)  
COOL  
1
2
3
4
5
6
7
8
9
10  
270 280 290 300 310 320 330 340 350 360  
140 152 160 170 180 200 224 244 274 280  
HEAT  
Difference in operation number  
Operation number  
2
28  
-45  
3
56  
-60  
4(MXZ-4A)  
84  
COOL  
HEAT  
-60  
Capacity code  
Indoor unit  
4
7
9
10 12  
09 12 15 17 24  
26  
<Correction>  
COOL  
DRY  
HEAT  
Discharge temperature  
2
2
Each correction  
• (Each gas pipe temperature thermistor - Minimum gas pipe temperature thermistor)  
1
• (Main indoor coil thermistor - Sub indoor coil thermistor)  
1 Perform this, when number of operation units is 2 units or more.  
1
1
MXZ-2A20NA-  
MXZ-3A30NA-  
and MXZ-4A36NA are excluded.  
,
2 Correct the LEV opening by discharge temperature.  
(1) LEV opening correction by discharge temperature  
The target discharge temperature is determined according to frequency zone and number of operation unit of the com-  
pressor.  
MXZ-2A20NA  
Target discharge temperature (°F)  
Number of operating unit  
Operation frequency  
of compressor (Hz)  
COOL  
COOL  
COOL  
HEAT  
HEAT  
HEAT  
1 unit  
95  
104  
120.2  
136.4  
149  
2 units  
136.4  
140  
1 unit  
122  
132.8  
140  
2 units  
122  
122  
132.8  
140  
140  
Minimum ~ 23  
24 ~ 38  
39 ~ 54  
55 ~ 69  
70 ~ 85  
149  
154.4  
158  
140  
140  
86 ~ Maximum  
158  
158  
140  
140  
MXZ-2A20NA-  
1
Target discharge temperature (°F)  
Number of operating unit  
Operation frequency  
of compressor (Hz)  
1 unit  
95  
104  
120.2  
136.4  
149  
2 units  
136.4  
140  
1 unit  
122  
132.8  
140  
2 units  
122  
122  
132.8  
140  
140  
Minimum ~ 23  
24 ~ 38  
39 ~ 54  
55 ~ 69  
70 ~ 85  
149  
154.4  
158  
158  
145.4  
150.8  
152.6  
86 ~ Maximum  
158  
140  
MXZ-3A30NA  
Target discharge temperature (°F)  
Number of operating unit  
Operation frequency  
of compressor (Hz)  
1 unit  
95  
104  
120.2  
136.4  
149  
154.4  
158  
2 units  
131  
131  
136.4  
140  
149  
154.4  
158  
163.4  
167  
3 units  
134.6  
134.6  
145.4  
149  
158  
163.4  
167  
1 unit  
125.6  
136.4  
149  
154.4  
154.4  
154.4  
154.4  
154.4  
154.4  
172.4  
2 unit  
143.6  
150.8  
165.2  
172.4  
172.4  
172.4  
172.4  
172.4  
172.4  
172.4  
3 units  
122  
131  
Minimum ~ 14  
15 ~ 23  
24 ~ 32  
33 ~ 41  
42 ~ 50  
51 ~ 59  
60 ~ 68  
69 ~ 77  
78 ~ 86  
140  
152.6  
161.6  
168.8  
168.8  
168.8  
168.8  
168.8  
167  
167  
167  
176  
179.6  
179.6  
87 ~ Maximum  
176  
27  
MXZ-3A30NA-  
MXZ-4A36NA  
1
Target discharge temperature (°F)  
COOL  
HEAT  
Operation frequency  
of compressor (Hz)  
Number of operating unit  
4 units  
4 units  
(MXZ-4A36)  
1 unit  
2 units  
3 units  
1 unit  
2 unit  
3 units  
(MXZ-4A36)  
140  
Minimum ~ 14  
15 ~ 23  
95  
131  
131  
136.4  
140  
149  
154.4  
158  
163.4  
167  
176  
134.6  
134.6  
145.4  
149  
158  
163.4  
167  
176  
179.6  
179.6  
125.6  
136.4  
149  
143.6  
150.8  
165.2  
172.4  
172.4  
172.4  
172.4  
172.4  
172.4  
172.4  
122  
131  
140  
152.6  
161.6  
168.8  
168.8  
168.8  
168.8  
168.8  
122  
122  
122  
122  
131  
140  
140  
140  
140  
140  
107.6  
120.2  
136.4  
149  
154.4  
158  
167  
167  
167  
140  
140  
24 ~ 32  
33 ~ 41  
42 ~ 50  
51 ~ 59  
60 ~ 68  
69 ~ 77  
78 ~ 86  
143.6  
149  
158  
154.4  
154.4  
154.4  
154.4  
154.4  
154.4  
172.4  
158  
161.6  
161.6  
161.6  
87 ~ Maximum  
Correct the LEV opening according to the difference between target discharge temperature and discharge temperature.  
MXZ-2A  
LEV opening correction (pulse)  
Discharge temperature (°F)  
More than Target discharge temperature+18  
Target discharge temperature + 18 to Target discharge temperature + 9  
Target discharge temperature + 9 to Target discharge temperature + 3.6  
Target discharge temperature + 3.6 to Target discharge temperature - 3.6  
Target discharge temperature - 3.6 to Target discharge temperature - 9  
Target discharge temperature - 9 to Target discharge temperature - 18  
Target discharge temperature - 18 or less  
COOL  
HEAT  
5
4
8
3
2
1
0
0
-1  
-3  
-4  
-1  
-2  
-3  
MXZ-3A MXZ-4A  
LEV opening correction (pulse)  
Discharge temperature (°F)  
COOL  
HEAT  
More than Target discharge temperature + 21.6  
4
2
1
6
2
1
Target discharge temperature + 21.6 to Target discharge temperature + 9  
Target discharge temperature + 9 to Target discharge temperature + 5.4  
Target discharge temperature + 5.4 to Target discharge temperature - 5.4  
Target discharge temperature - 5.4 to Target discharge temperature - 9  
Target discharge temperature - 9 to Target discharge temperature - 21.6  
Target discharge temperature - 21.6 or less  
0
0
-1  
-3  
-8  
-1  
-2  
-8  
(2) Separate correction (COOL,DRY)  
(Correction by the separate super heat)  
a) Correct the LEV separately by temperature difference between each gas pipe temperature and the minimum gas pipe  
temperature of all.  
Calculate each super heat of the unit from the expression below;  
(Super heat) = (Each gas pipe temperature) - (Minimum gas pipe temperature)  
Separate correction is performed according to each super heat in the table below.  
MXZ-2A20NA  
MXZ-3A30NA  
LEV opening  
correction (pulse)  
LEV opening  
correction (pulse)  
Superheat  
Superheat  
more than 16.2  
10.8 to 16.2  
5.4 to 10.8  
3
2
1
0
more than 16.2  
10.8 to 16.2  
5.4 to 10.8  
12  
8
4
5.4 or less  
5.4 or less  
0
28  
b) Correct the LEV separately by temperature difference “ RT” between main/sub indoor coil thermistor.  
LEV opening  
RT  
correction (pulse)  
10.8 RT  
7.2 RT < 10.8  
RT < 7.2  
2
1
1
In addition, decrease the target discharge temperature corresponding RT.  
Temperature to be  
decreased (°F)  
RT  
10.8 RT  
7.2 RT< 10.8  
RT < 7.2  
18  
9
9
3-3. OPERATIONAL FREQUENCY RANGE  
MXZ-2A20NA  
COOL (Hz)  
HEAT (Hz)  
Max.  
92  
Number of operating  
unit  
Capacity code  
DRY (Hz)  
Min.  
20  
20  
20  
20  
30  
30  
30  
20  
Max.  
65  
85  
100  
100  
105  
105  
105  
105  
Min.  
48  
48  
48  
48  
58  
58  
58  
58  
Defrost  
92  
92  
100  
100  
100  
100  
100  
100  
4
7
9,10  
12  
8 ~ 10  
11 ~ 13  
14 ~ 16  
17 ~  
25  
30  
75  
75  
52  
52  
52  
100  
92  
100  
100  
112  
112  
112  
112  
1
2
1
MXZ-2A20NA-  
COOL (Hz)  
HEAT (Hz)  
Max.  
92  
Number of operating  
unit  
Capacity code  
DRY (Hz)  
Min.  
20  
20  
20  
20  
30  
30  
30  
30  
Max.  
65  
85  
93  
93  
93  
93  
93  
93  
Min.  
48  
48  
48  
48  
58  
58  
58  
58  
Defrost  
92  
92  
92  
92  
101  
101  
101  
101  
4
7
9,10  
12  
8 ~ 10  
11 ~ 13  
14 ~ 16  
17 ~  
35  
34  
75  
75  
52  
52  
52  
93  
92  
92  
92  
110  
110  
110  
110  
1
2
MXZ-3A30NA  
COOL (Hz)  
HEAT (Hz)  
Number of operating  
unit  
Capacity code  
DRY (Hz)  
Min.  
15  
15  
15  
15  
24  
24  
24  
24  
52  
Max.  
58  
58  
62  
68  
80  
80  
80  
80  
90  
Min.  
22  
22  
22  
22  
35  
35  
35  
35  
39  
Max.  
48  
48  
62  
90  
70  
90  
94  
94  
94  
Defrost  
48  
48  
58  
58  
58  
58  
58  
58  
4
7
9,10  
12  
8 ~ 10  
11 ~ 13  
14 ~ 16  
17 ~  
12 ~  
20  
25  
44  
44  
31  
31  
31  
59  
65  
1
2
3
58  
29  
1
MXZ-3A30NA-  
MXZ-4A  
COOL (Hz)  
Min.  
HEAT (Hz)  
Max.  
70  
Number of operating  
unit  
Capacity code  
DRY (Hz)  
Max.  
58  
58  
71  
80  
80  
80  
80  
80  
80  
90  
90  
Min.  
20  
20  
20  
20  
20  
20  
20  
20  
20  
20  
20  
Defrost  
58  
58  
58  
58  
58  
58  
58  
58  
4
7
9,10  
12  
8 ~ 10  
11 ~ 13  
14 ~ 16  
17 ~  
12 ~  
12 ~  
16 ~  
25  
25  
25  
25  
25  
25  
25  
25  
25  
25  
25  
25  
25  
25  
35  
31  
31  
42  
42  
52  
52  
52  
70  
80  
80  
80  
80  
80  
80  
80  
1
2
3 (MXZ-3A)  
3 (MXZ-4A)  
4 (MXZ-4A)  
58  
58  
58  
103  
113  
3-4. HEAT DEFROSTING CONTROL  
(1) Starting conditions of defrosting  
When the following conditions a) ~ c) are satisfied, the defrosting starts.  
a) The defrost thermistor reads 26.6 °F or less.  
b) The cumulative operation time of the compressor has reached any of the set values (31, 35, 45, 55, 65, 75, 85, 95,  
105, 115, 150 minutes).  
c) More than 5 minutes have passed since the start-up of the compressor.  
Set value of compressor operation time (hereinafter referred to as defrost interval)  
This is decided by the temperature of defrost thermistor and ambient temperature thermistor, the previous defrosting  
time. For example, the first defrost interval is 40 minutes long, and the second is 45 minutes long. The third and sub-  
sequent intervals are set to be longer, and less frequent, depending on defrosting time.  
The third and subsequent defrost intervals follow any of the three patterns 5 or 10 to 20 minutes longer, the same,  
or 5 or 10 to 20 minutes shorter compared with the previous defrost interval  
shortest 40 minutes.  
with the longest 125 minutes and the  
(2) Releasing conditions of defrosting  
Defrosting is released when any of the following conditions is satisfied:  
a) The defrost thermistor continues to read 50.7 °F.  
b) Defrosting time exceeds 10 minutes.  
c) Any other mode than HEAT mode is set during defrosting.  
3-5. DISCHARGE TEMPERATURE PROTECTION CONTROL  
This protection controls the compressor ON/OFF and operation frequency according to temperature of the discharge tempera-  
ture thermistor.  
(1) Compressor ON/OFF  
When temperature of the discharge temperature thermistor exceeds 240.8 °F, the control stops the compressor.  
When temperature of the discharge temperature thermistor is 176 °F (2A/3A30NA)/ 212 °F (3A30NA- 1 /4A) or less, the  
controls starts the compressor.  
(2) Compressor operation frequency  
When temperature of the discharge temperature thermistor is expected to be higher than 240.8 °F, the control decreases  
12 Hz from the current frequency.  
When temperature of the discharge temperature thermistor is expected to be higher than 231.8 °F and less than 240.8 °F,  
the control decreases 6 Hz from the current frequency.  
When temperature of the discharge temperature thermistor is expected to be higher than 219.2 °F and less than 231.8 °F,  
the control is set at the current frequency.  
3-6. OUTDOOR FAN CONTROL  
Fan speed is switched according to the number of operating indoor unit and the compressor frequency.  
<Relation between compressor frequency and fan speed>  
Fan speed  
Compressor frequency (Hz)  
Down  
Up  
High  
Down  
Up  
MXZ-2A  
MXZ-3A30NA  
30  
40  
Low  
1
MXZ-3A30NA-  
MXZ-4A  
Min. Compressor frequency Max.  
40  
50  
NOTE : When the indoor coil thermistor is 134.6 ˚F or more on HEAT operation, fan speed is fixed to Low speed.  
Or, the indoor coil thermistor is 113 ˚F or less on HEAT operation, fan speed is back to normal.  
30  
3-7. PRE-HEAT CONTROL  
MXZ-2A20NA- MXZ-3A30NA-  
1
1
MXZ-4A36NA  
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  
68 °F  
30min.  
30 min.  
30 min.  
30 min.  
30 min.  
30 min. 15 min. 30 min.15 min. 30 min.  
Pre-heat  
ON  
OFF  
Start  
Stop  
When outside  
temperature is  
above 68 °F  
Breaker ON  
operation operation  
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 68 °F or below, pre-heat control is ON for 30 min."  
When outside temperature is 69.8 °F 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.  
3-8. COOL OPERATION  
1. Thermostat control  
Thermostat is ON or OFF by difference between room temperature and set temperature.  
Room temperature minus  
set temperature (Initial)  
Room temperature minus  
set temperature (During operation)  
Thermostat  
ON  
OFF  
-1.8 °F or more  
less than-1.8 °F  
-1.8 °F  
-1.3 °F  
2. Coil frost prevention  
The compressor operational frequency is controlled to prevent the indoor heat exchanger temperature from falling exces-  
sively.  
Compressor is turned OFF for 5 minutes when temperature of indoor coil thermistor continues 37.4 °F or less for 5 min-  
utes or more.  
31  
3-9. DRY OPERATION  
1. Thermostat control  
Thermostat is ON or OFF by difference between room temperature and set temperature.  
Room temperature minus  
set temperature (Initial)  
Room temperature minus  
set temperature (During operation)  
Thermostat  
ON  
OFF  
-1.8 °F or more  
less than-1.8 °F  
-1.8 °F  
-1.3 °F  
2. Coil frost prevention  
Coil frost prevention is as same as COOL mode. (3-8.2.)  
3-10. HEAT OPERATION  
1. Thermostat control  
Thermostat is ON or OFF by difference between room temperature and set temperature.  
Room temperature minus  
set temperature (Initial)  
Room temperature minus  
set temperature (During operation)  
Thermostat  
ON  
OFF  
less than 3.6 °F  
3.6 °F or more  
3.6 °F  
3 °F  
2. High pressure protection  
In HEAT operation the indoor coil thermistor detects the temperature of the indoor heat exchanger. The compressor opera-  
tional frequency is controlled to prevent the condensing pressure from increasing excessively.  
HEAD OFFICE: TOKYO BLDG.,2-7-3, MARUNOUCHI, CHIYODA-KU, TOKYO 100-8310, JAPAN  
Copyright 2006 MITSUBISHI ELECTRIC ENGINEERING CO.,LTD  
Distributed in Feb. 2008. No. OBT16 REVISED EDITION-B 6  
Distributed in May 2007. No. OBT16 REVISED EDITION-A 7  
Distributed in Apr. 2006. No. OBT16 7  
Made in Japan  
New publication, effective Feb. 2008  
Specifications subject to change without notice.  

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