Mitsubishi Heavy Industries SRF25ZS-W User manual

SERVICE MANUAL
INVERTER FLOOR STANDING TYPE
RESIDENTIAL AIR-CONDITIONERS
(Split system, air to air heat pump type)
SRF25ZS-W / SRC25ZS-W2
SRF35ZS-W / SRC35ZS-W2
SRF50ZSX-W / SRC50ZSX-W2
Manual No.’20 • SRF-SM-311

'20 • SRF-SM-311
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CONTENTS
1. OUTLINE OF OPERATION CONTROL BY MICROCOMPUTER
(10) Timer operation
(9) Air outlet selection
(1) Operation control function by wireless remote control
(8) Flap control
(5) Selection of the annual cooling function
(4) Installing two air-conditioners in the same room
(3) Auto restart function
(2) Unit ON/OFF button
(11) Silent mode
(12) Night setback
(13) Outline of heating operation
(15) Outline of dehumidifying (DRY) operation
(14) Outline of cooling operation
(7) Economy operation
(6) High power operation
(16) Outline of automatic operation
(17) Protective control function
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(10) How to make sure of wireless remote control
(12) Outdoor unit inspection points
(11)
Inspection procedure for blown fuse on the indoor and outdoor unit PCB
(8) Phenomenon observed after short-circuit, wire breakage on sensor
(9) Checking the indoor electrical equipment
3. ELECTRICAL WIRING
4. PIPING SYSTEM
(6) Service mode (Trouble mode access function)
(7) Inspection procedures corresponding to detail of trouble
(4) Troubleshooting procedure (If the air-conditioner runs)
(3) Troubleshooting procedure (If the air-conditioner does not run at all)
(2) Items to check before troubleshooting
(5) Self-diagnosis table
(1) Cautions
2. MAINTENANCE DATA

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ONOCEREMITNUR
ON
/ OFF
HI POWER
Unit display section
ECONO light (orange)
Illuminates during ECONOMY operation.
HI POWER light (green)
Illuminates during HIGH POWER operation.
TIMER light (yellow)
Illuminates during TIMER operation.
This button can be used for turning on/off the unit when
remote control is not available.
Wireless remote control signal receiver
Unit ON/OFF button
RUN (HOT KEEP) light (green)
•Illuminates during operation.
•
Blinks when airflow stops due to the ‘HOT
KEEP’
and ‘ CLEAN operation ’.
ON
OFF
1.5 sec.
0.5 sec.
HOT KEEP
3 sec.
1 sec.
ON
OFF
CLEAN operation
ON
OFF
0.5 sec.
0.5 sec.
Operation mode
invalid
OPERATION MODE select button
ON/OFF (luminous) button
TEMPERATURE button
AIR FLOW (UP/DOWN) button
TIME SET UP switch
SLEEP button
CLEAN switch
ON TIMER button
TIMER button
ACL switch
PROGRAM button
Operation section
HI/ECO button
SILENT button
OFF TIMER button
WEEKLY button
FAN SPEED button
NIGHT SETBACK button
SET/Child Lock button
CANCEL button
Transmission section
Each time the button is pressed, the mode
changes.
•The above illustration shows all controls, but in
practice only the relevant parts are shown.
Press to start operation, press again to
stop.
This button sets the room temperature.
This button changes the air flow (up/down)
direction.
This switch is for setting the time.
This button selects SLEEP operation.
This switch selects the CLEAN
operation.
This button selects ON TIMER operation.
This buttions is used for setting the cur-
rent time and timer function.
Switch for resetting microcomputer.
This button sets WEEKLY TIMER.
This button changes the HIGH POWER/
ECONOMY operation.
This buttion changes the SILENT
operation.
This button selects OFF TIMER
operation.
This button switches the WEEKLY
TIMER to ON/OFF.
Each time the button is pressed, the fan
speed changes.
This button sets NIGHT SETBACK
operation.
Use this button to set the timer and
Child Lock.
This button cancels the ON timer, OFF
timer, and SLEEP operation.
1. OUTLINE OF OPERATION CONTROL BY MICROCOMPUTER
(1) Operation control function by wireless remote control
Unit display section
AIR SELECTION button
AIR OUTLET SELECTION light (green)
Illuminates during upper air outlet operation.
TIMER light (yellow)
Illuminates during TIMER operation.
This button can be used for turning on/off the unit when
remotecontrol is not available.
HI POWER Light (green)
Illuminates duringHIGH POWER operation.
Blinks during heating preparation.
Unit ON/OFF button RUN (HOT KEEP) light (green)
•Illuminates during operation.
•
Blinks when airflow stops due to the ‘HOT
KEEP’
, ‘ CLEAN operation ’and ‘ operation
mode invalid
’.
Remote control signal receiver
1.5 sec.
ON
OFF
0.5 sec.
HOT KEEP
3 sec.
1 sec.
ON
OFF
CLEAN operation
ECONO light (green)
Illuminates duringECONOMY operation.
Use this button to switch between the combination of
upper and lower air outlets and upper air outlet.
Operation mode
invalid
ON
OFF
0.5 sec.
0.5 sec.
1.5 sec.
ON
OFF
0.5 sec.

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(2) Unit ON/OFF button
When the wireless remote control batteries become weak, or if the wireless remote control is lost or malfunctioning, this button
may be used to turn the unit on and off.
(a) Operation
Push the button once to place the unit in the automatic mode. Push it once more to turn the unit off.
(b) Details of operation
The unit will go into the automatic mode in which it automatically determines, from indoor temperature (as detected
by sensor), whether to go into COOL, DRY or HEAT modes.
(3) Auto restart function
(a) Auto restart function records the operational status of the air-conditioner immediately prior to be switched off by a power cut,
and then automatically resumes operations after the power has been restored.
(b) The following settings will be cancelled:
(i) Timer settings
(ii) HIGH POWER operation
Notes (1) Auto restart function is set at on when the air-conditioner is shipped from the factory. Consult with
your dealer if this function needs to be switched off.
(2) When power failure ocurrs, the timer setting is cancelled. Once power is resumed, reset the timer.
(3)
If the jumper wire (J170) “AUTO RESTART” is cut, auto restart is disabled. (See the diagram at right)
Jumper wire (J170)
Function
Operation mode
Indoor temperature
setting
Fan speed Flap/Louver Timer switch
COOL About 24ºC
Auto Auto Continuous
DRY About 25ºC
HEAT About 26ºC
Unit ON/OFF button
Reception
Pip
When two air-conditioners are installed in the room, use setting when the two air-conditioners are not operated with one wireless
remote control. Set the wireless remote control and indoor unit.
(a)Setting the wireless remote control
(i) Pull out the cover and take out batteries.
(ii) Disconnect the switching line next to the battery with wire cutters.
(iii) Insert batteries, Close the cover.
(b)Setting an indoor unit
(i) Turn off the power source, and turn it on after 1 minute.
(ii) Point the wireless remote control that was set according to the procedure
described on the left side at the indoor unit and send a signal by pressing
the ACL switch on the wireless remote control.
Since the signal is sent in about 6 seconds after the ACL switch is pressed,
point the wireless remote control at the indoor unit for some time.
(iii) Check that the reception buzzer sound "Pip" is emitted from the indoor unit.
At completion of the setting, the indoor unit emits a buzzer sound "Pip".
(If no reception tone is emitted, start the setting from the beginning again.)
Disconnect
(4)Installing two air-conditioners in the same room

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(a) The annual cooling control is valid from factory default setting. It is possible
to disable by cutting jumper wire (J172), or changing the setting of DIP switch
(SW2-4) on the interface kit (option) PCB if it is connected.
Note: (1) Default states of the jumper wire (J172) and the interface kit at the shipping from factory – On the
PCB, the DIP switch (SW2-4) is set to enable the annual cooling function.
(2) To cancel the annual cooling setting, consult your dealer.
(b) Content of control
(i) If the outdoor air temperature sensor (TH3) detects below 5°C, the indoor
unit speed is switched to 8th step.
(ii) If the outdoor air temperature sensor (TH3) detects higher than 7°C, the indoor unit speed is changed to the normal con-
trol speed.
Pressing the HI POWER/ECONO button intensies the operating power and initiates powerful cooling and heating operation
for 15 minutes continuously. The wireless remote control displays and the FAN SPEED display disappears.
(a) During the HIGH POWER operation, the room temperature is not controlled. When it causes an excessive cooling and
heating, press the HI POWER/ECONO button again to cancel the HIGH POWER operation.
(b) HIGH POWER operation is not available during the DRY and the program timer operations.
(c) When HIGH POWER operation is set after ON TIMER operation, HIGH POWER operation will start from the set time.
(d) When the following operation are set, HIGH POWER operation will be canceled.
①When the HI POWER/ECONO button is pressed again. ④When the SILENT botton is pressed.
②When the operation mode is changed. ⑤When the NIGHT SETBACK botton is pressed.
③When it has been 15 minutes since HIGH POWER operation has started.
(e) Not operable while the air-conditioner is OFF.
(f) After HIGH POWER operation, the sound of refrigerant owing may be heard.
Pressing the HI POWER/ECONO button initiate a soft operation with the power suppressed in order to avoid an excessive
cooling or heating. The unit operate 1.5°C higher than the setting temperature during cooling or 2.5°C lower than that during
heating. The wireless remote control displays ECONO mark and the FAN SPEED display disappears.
(a) It will go into ECONOMY operation at the next time the air-conditioner runs in the following cases.
①When the air-conditioner is stopped by ON/OFF button during ECONOMY operation
②When the air-conditioner is stopped in SLEEP or OFF TIMER operation during ECONOMY operation
③When the operation is retrieved from CLEAN operation
(b) When the following operation are set, ECONOMY operation will be canceled.
①When the HI POWER/ECONO button is pressed again
②When the operation mode is changed DRY to FAN
③When the NIGHT SETBACK botton is pressed
(c) Not operable while the air-conditioner is OFF.
(d) The setting temperature is adjusted according to the following table.
Jumper wire
(J172)
Interface kit
(SC-BIKN2-E)
SW2-4
Function
Shorted ON Enabled
Shorted OFF Disabled
Open ON Disabled
Open OFF Disabled Jumper wire (J172)
ON
5 7
OFF
Outdoor air temperature ( C)
①at the start of operation
②one hour after the start of operation
③two hours after the start of operation
Temperature
adjustment
Cooling Heating
①＋0.5 ①−1.0
②＋1.0 ②−2.0
③＋1.5 ③−2.5
Mode
Item
(5) Selection of the annual cooling function
(6) High power operation
(7) Economy operation

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(8) Flap control
Control the ap by AIR FLOW 
(UP/DOWN) button on the wireless remote control.
(b) Swing
(i) Swing ap
Flap moves in upward and downward directions continuously.
(c) Memory flap (Flap stopped)
When you press the AIR FLOW button once while the ap is operating, it stops swinging at the position. Since this angle is
memorized in the microcomputer, the ap will automatically be set at this angle when
the next operation is started.
(d) When not operating
The ap returns to the position of air ow directly below, when operation has stopped.
COOL , DRY, FAN
Remote control
display
HEAT
Approx. 60°
Approx. 44°
Approx. 50°
Approx. 32°
Approx. 38°
Approx. 21.5° Approx. 5°
Approx. 21.5°
Approx. 12°
Approx. 12°
󱓻

Angle of Flap from horizontal
(Swing)(Flap stopped)
Approx.60°
Approx.12°
Approx.44°
Approx.
5°
In HEAT operation In COOL, DRY, FAN operation
Approx. 45°
Approx. 75°
Approx.
5°
Approx. 60°
(a) Flap
Each time when you press the AIR FLOW 
(UP/DOWN) button the mode changes as follows.
AIR OUTLET SELECTION
light : OFF
AIR OUTLET SELECTION
light : ON
Upper air outletUpper and lower air outlets
AIR SELECTION button
(9) Air outlet selection
(b) Auto air outlet selection
(i) COOL, DRY operation
1) In case both lower and upper outlets operation is selected in Cooling or Dry
operation, both outlets will be kept for sixty minutes after the start or until
indoor temperature is below the setting point. And then the air outlet will change
to the upper outlet. That state will be maintained until switch is turned off.
2) In case both outlets operation with auto fan speed mode is selected, the upper
outlet will be kept for ten minutes after the start or until indoor temperature is
close to reaching the setting point . And then the air outlet will change to both
outlets in order to spread comfort air to every corner.
(a) AIR SELECTION button can switch between the combination of upper and lower air outlets and upper air
outlet. Not operable while the air-conditioner is OFF.
(i) Each time the AIR SELECTION button is pressed. The combination of the
upper and lower air outlets and the upper air outlet can be switched.
(ii) When the upper air outlet is selected, AIR OUTLET SELECTION light on
the unit display area will light green.

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(ii) HEAT operation
1) In case both lower and upper outlets operation with auto fan speed mode is selected, the
lower outlet will be kept for twenty minutes after the start or until room temperature is
close to reaching the setting point . And then the air outlet will change to both outlets.
That state will be maintained until the switch is turned off.
2) Automatic adjustment of lower air outlet direction prevents stirring up of warm air
and keeps optimum comfort at oor level.
(10) Timer operation
(a) Comfortable timer setting (ON timer)
If the timer is set at ON when the operation select switch is set at the cooling or heating, or the cooling or heating in auto
mode operation is selected, the comfortable timer starts and determines the starting time of next operation based on the initial
value of 15 minutes and the relationship between the room temperature at the setting time (temperature of room temperature
sensor) and the setting temperature.
(b) Sleep timer operation
Pressing the SLEEP button causes the temperature to be controlled with respect to the set temperature.
(c) OFF timer operation
The Off timer can be set at a specic time (in 10-minute units) within a 24-hour period.
(d) Weekly timer operation
Timer operation (ON timer, OFF timer) can be set up to 4 times a day for each weekday.
(11) Silent mode
As “Silent mode start” signal is received from the wireless remote control, it operates by dropping the outdoor fan tap and the
compressor command speed.
(12) Night setback
As “Night setback” signal is received from the wireless remote control, the heating operation starts with the setting temperature
at 10℃.
Outdoor fan tap
(Upper limit)
Compressor command
speed (Upper limit)
Cooling Heating Cooling Heating Cooling Heating
SRF25ZS-W SRF35ZS-W SRF50ZSX-W
4th speed
37 rps
4th speed
49 rps
5th speed
46 rps
4th speed
56 rps
5th speed
43 rps
5th speed
48 rps
(a) Operation of major functional components in heating mode
ON OFF
ON ON
ON OFF
(few minutes ON)
ON ON(HOT KEEP)
OFF
OFF
(3 minutes ON)
OFF
OFF
Thermostat ON Thermostat OFF Failure
Heating
Compressor
Indoor fan motor
Outdoor fan motor
4-way valve
(13) Outline of heating operation

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(b) Details of control at each operation mode (pattern)
(i) Fuzzy operation
Deviation between the room temperature setting correction temperature and the return air temperature is calculated in
accordance with the fuzzy rule, and used for control of the air capacity and the compressor speed.
When the defrost operation, protection device, etc. is actuated, operation is performed in the corresponding mode.
(ii) Hot keep operation
If the hot keep operation is selected during the heating operation, the indoor blower is controlled based on the temperature
of the indoor heat exchanger (Th2) to prevent blowing of cool wind.
However, if the fan speed setting is Hi and room temperature is 19ºC or higher, this control is not executed.
12
-
110rps
12
-
110rps
12
-
80rps
12
-
70rps
SRF50ZSX-W
20
-
115rps
20
-
115rps
20
-
98rps
20
-
92rps
SRF35ZS-W
20
-
102rps
20
-
102rps
20
-
76rps
20
-
66rps
SRF25ZS-W
Model
Fan speed
Auto
MED
HI
LO
12
-
60rps20
-
80rps20
-
58rps
ULO
(c) Defrost operation
(i) Starting conditions (Defrost operation can be started only when all of the following conditions are satised.)
1) After start of heating operation
When it elapsed 35 minutes (Accumulated compressor operation time)
2) After end of defrost operation
When it elapsed 35 minutes (Accumulated compressor operation time)
3) Outdoor heat exchanger temperature sensor (TH1)
When the temperature has been below -5ºC for 3 minutes continuously
4) The difference between the outdoor air sensor temperature and the outdoor heat exchanger sensor temperature (TH2-TH1)
¡The outdoor air temperature ≧0°C (SRF50 : ≧-2ºC) : 7°C or higher
¡
-15°C ≦The outdoor air temperature ＜0°C (SRF50 : ≧ -2ºC) : 3/15 × The outdoor air temperature + 7°C or higher (SRF25)
4/15 × The outdoor air temperature + 7°C or higher (SRF35, 50)
¡The outdoor air temperature < -15°C : -5°C or higher
-20
-20 -15 -10 -5 0 5 10
-15
-10
-5
0
Outdoor air temperature (℃)
Outdoor heat exchanger temperature (
℃)
-20
-20 -15 -10 -5 0 5 10
-15
-10
-5
0
Outdoor air temperature (℃)
Outdoor heat exchanger temperature (℃)
Defrost operation
start
Defrost operation
start
Defrost operation start temperature
Defrost operation start temperature
Models 20～35 Model 50
-20
-20 -15 -10 -5 0 5 10
-15
-10
-5
0
Outdoor air temperature (℃)
Outdoor heat exchanger temperature (℃)
-20
-20 -15 -10 -5 0 5 10
-15
-10
-5
0
Outdoor air temperature (℃)
Outdoor heat exchanger temperature (℃)
Defrost operation
start
Defrost operation
start
Defrost operation start temperature
Defrost operation start temperature
Models 20～35 Model 50
SRF25 SRF35

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(14) Outline of cooling operation
ON OFF OFF
OFF OFF OFF
ON OFF
(few minutes ON)
OFF
(few minutes ON)
ON ON OFF
Thermostat ON Thermostat OFF Failure
Cooling
Compressor
Indoor fan motor
Outdoor fan motor
4-way valve
(a) Operation of major functional components in cooling mode
(b) Detail of control in each mode (Pattern)
(i) Fuzzy operation
During the fuzzy operation, the air ow and the compressor speed are controlled by calculating the difference between
the room temperature setting correction temperature and the return air temperature.
12
-
86rps
12
-
86rps
12
-
58rps
12
-
48rps
SRF50ZSX-W
15
-
104rps
15
-
104rps
15
-
71rps
15
-
58rps
SRF35ZS-W
15
-
72rps
15
-
72rps
15
-
48rps
15
-
40rps
SRF25ZS-W
Model
Fan speed
12
-
38rps15
-
46rps15
-
34rps
Auto
MED
HI
LO
ULO
-20
-20 -15 -10 -5 0 5 10
-15
-10
-5
0
Outdoor air temperature (
℃
)
Outdoor heat exchanger temperature (
℃)
Defrost operation
start
Defrost operation start temperature
Model SRF50
SRF50
5) During continuous compressor operation
In addition, when the speed command from the indoor control of the indoor unit during heating operation has counted 0
rps 10 times or more and all conditions of 1), 2) and 3) above and the outdoor air temperature is 3°C or less are satised
(note that when the temperature for outdoor heat exchanger temperature sensor (TH1) is -5°C or less: 62 rps or more,
-4°C or less: less than 62 rps), defrost operation is started.
(ii) Ending conditions (Operation returns to the heating cycle when either one of the following is satised.)
1) Outdoor heat exchanger temperature sensor (TH1) : 13ºC (SRF50 : 10°C) or higher
2) Continued time of defrost operation → For more than 15 minutes
Max. 15 minutes
Heating operatio
n
¡Defrost operation
Depends on an operation condition, the time can be longer than 7 minutes.
2-7 minutes 
Hot keep operation

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(16) Outline of automatic operation
(15) Outline of dehumidifying (DRY) operationion
(a) Purpose of DRY mode
The purpose is "Dehumidication", and not to control the humidity to the target condition.
Indoor/outdoor unit control the operation condition to reduce the humidity, and also prevent over cooling.
(b) Outline of control
(i) Indoor fan speed and compressor are controlled by the area which is selected by the temperature difference.
(ii) The indoor unit check the current area by every 5 minutes, and operate by the next checking.
(c) Other
When the outside temperature and room temperature is low for cooling operation, indoor unit can not operate in cooling, and
dehumidify. In this case, the units operate in heating to rise the room temperature, and after that start DRY operation.
Indoor fan speed
Area
DCBA
Me speed
Indoor fan
speedULo(Lo) speed
STOP
Limited䠄Lower than
normal cooling operation䠅
Compressor
Limited
speed
Minimum 䠄Lower than the speed in ”Area A”䠅
STOP
set temperature
Difference between set temperature and return air temperature
Heating
Cooling
SP: Setting temperature
SP
Indoor air
temperature (˚C)
28
Outdoor air temperature (˚C)
(b) Operation mode is changes when keep cooling and heating thermostat off 20 minutes and be satisfied following conditions.
If the setting temperature is changed with the remote control, the operation mode is judged immediately.
(c) When the unit is started again within one hour after the stop of automatic operation or when the automatic operation is
selected during heating, cooling or dehumidifying operation, the unit is operated in the previous operation mode.
(d) Setting temperature can be adjusted within the following range. There is the relationship as shown below between the signals
of the wireless remote control and the setting temperature.
(e) When the unit is operated automatically with the wired remote control, the cooling operation iscontrolled according to
the display temperatures while the setting temperature is compensated by ＋2℃ during heating.
※It can not be changed to heating mode if outdoor air temperature is 28℃or higher.
Heating SP: Setting temperature
Indoor air temperature−Setting temperature (˚C)
Keep operation
mode
Cooling
Signals of wireless remote control (Display)
18 19 20 21 22 23 24 25 26 27 28 29 30
18 19 20 21 22 23 24 25 26 27 28 29 30
20 21 22 23 24 25 26 27 28 29 30 31 32
Setting
temperature
Cooling
Heating
SP＋1
SP−1
Unit : ℃
(a) Determination of operation mode
Operation mode is determined by indoor air temperature and outdoor air temperature as following.