Panasonic Cs Kexxnb4x Cz 18bt1u Service Manual

							NOTE
7-3-3. Remove the ceiling panel.
(1)  Open the clamp (4 locations) and remove the 2 lead wires from the clamps. (Fig. 6)
(2)  Remove the 4 screws fixing the corner cover (at 3 locations) and indicator cover (at 1 location). (Fig. 6)
(3)  Press the center 1 of the cover and remove the cover with the section 2 pulled down. (Fig. 7)
(4)  Remove the strap (3 locations) from the hook on the ceiling panel. (Fig. 8)
There is no strap on the indicator cover.
(5)  Remove the bolt (4 locations) with a washer and remove the ceiling panel. (Fig. 9)
Screw
Bolt
Bolt Screw
Indicator
coverCorner cover
Corner cover Corner cover Clamp
 ClampPull down 
section 2.  Lead wire
Cover
Center 1Fig.6 Fig.7
Fig.8 Fig.9
Remove the strap 
from the hook. Strap
41 
						

							123
7-3-4.  Remove the indoor air temperature sensor.
(1)  Disconnect the connector CN08 (ROOM 2P) in the control box and remove the indoor air temperature 
sensor. (Fig. 10)
7-3-5. Remove the power box and control box.
(1)  Remove a screw and remove the terminal cover. (Fig. 11)
(2)  Remove the 2 screws and remove the power box cover. (Fig. 11)
(3)  Disconnect the power lines (No. 1 and No. 2) / signal line (No. 3) and ground cable from the terminals in 
the power box. (Fig. 12)
Indoor air temperature sensor
CN08
Terminal
Fig.10
Fig.11
Fig.12
Ground cable Terminal cover
Screw Screw
Power box cover
Power lines / Signal line
42 
						

							12 3
(4)  Disconnect the connector CN07 (DP 2P) in the power box. (Fig. 13)
  Remove a screw and disconnect the ground cable. (Fig. 13)
(5)  Disconnect the connector CN03 (DCM 6P) in the power box. (Fig. 14)
(6)  Remove the 4 screws and remove the power box. (Fig. 14)
(7)  Disconnect the connectors CN06 (FS 3P) and CN09 (COIL-1 2P) in the control box. (Fig. 15)
(8)  Remove the 2 screws and remove the control box. (Fig. 15)
Fig.13
Fig.14
Fig.15
Screw
Screw
Screw
Screw
Screw
CN06 CN03ScrewScrew Ground cable
CN07
CN09
43 
						

							For the removal of the following components, perform any work after removing the indoor 
unit (main body) from the ceiling.
    Main body lower section      Heat exchanger sensor      Drain pump
    Float switch      Turbo fan      Fan motor
    Heat exchanger 
1.  Perform the work after draining the water to prevent the water leakage from the drain pan.
 
• Put a bucket, etc., under the drain cap and remove the drain cap to drain the water. 
    (Fig. 16)
2.  Refer to the installation instructions for recovery of refrigerant or removal of the power
  cable or tubing.
7-3-6.  Remove the main body lower section.
(1)  Remove the 4 screws. (Fig. 16)
(2)  Remove the 2 screws. (Fig. 17)
(3)  Disconnect the connector CN03 (DCM 6P) in the power box. (Fig. 18)
(4)  Lift the main body lower section and remove it from the main body upper section.
Screw
Fig.16
Fig.18 Fig.17
Drain cap
Main body lower section Main body lower section
Screw Screw
Main body lower section
Main body 
upper section
Screw
CN03 Screw
NOTE
44 
						

							7-3-7. Remove the heat exchanger sensor.
(1)  Remove the heat exchanger sensor from the sensor holder. (Fig. 19) 
7-3-8. Remove the drain pump and float switch.
(1)  Remove the 2 screws (Fig. 20)
(2)  Loosen the clamp and disconnect the drain hose from the drain pump. (Fig. 20)
(3)  Remove the drain pump from the main body upper section. (Fig. 20)
(4)  Remove a nut and remove the float switch. (Fig. 21)
Heat exchanger sensor
Fig.20 Fig.21Fig.19
Holder
Drain pumpScrew
ClampFloat switch
Nut
Drain hose
45 
						

							7-3-9. Remove the turbo fan and fan motor.
(1)  Remove a nut and remove the turbo fan. (Fig. 22)
(2)  Remove the 2 screws and 3 nuts, and remove the fan motor. (Fig. 23) 
7-3-10. Remove the heat exchanger.
(1)  Remove the 3 screws. (Fig. 24)
(2)  Remove the 3 screws. (Fig. 25)
(3)  Remove the heat exchanger from the main body upper section with the heat exchanger lifted.Fig.22 Fig.23
Fig.24 Fig.25
Turbo fan
NutScrew Nut
Fan motor
Screw
Screw Heat exchanger
Screw Main body 
upper section
46 
						

							Emergency operation SENSOR DRY
AUTO cooling/heating operation
  Selecting the operation mode  During DRY operation, the system adjusts the room 
temperature and fan speed according to the conditions in the 
room, in order to maintain a comfortable room environment.
SENSOR DRY operation
  •  DRY operation is as shown in the figure below.
PAM-    control
•  In order to further improve inverter performance, control is 
switched between PWM control at low operation speeds, and 
PAM control at high operation speeds, making the most 
effective use of power.   The compressor operation frequency varies.
  The indoor fan operates with 1/f fluctuation.
  The compressor operates at a low operating frequency.
  The indoor fan operates with 1/f fluctuation.
•  Monitoring operation takes place when the room temperature 
is below 59°F
(15°C), or more than 5°F(3°C) below the set 
temperature.
•   When the monitoring range is entered, the compressor stops, 
and the indoor fan operates with 1/f fluctuation.
DRY A
DRY B
Monitor
Conditions are monitored at all 
times when the room temperature 
is below 59°F(15°C). Load
COOL zone
A zone
B zone
Emergency operation is available when the remote 
controller malfunctions, has been lost, or otherwise 
cannot be used.
•  The set temperature is 4°F(2°C) below the detected room 
temperature in the case of cooling operation, and 4°F(2°C) 
above the room temperature in the case of heating 
operation. The flap and fan speed settings are AUTO.
(GREEN) (RED) (Lamp Off)COOL HEAT STOP
•  When AUTO mode is selected, the microprocessor calculates 
the difference between the set temperature and the room 
temperature, and automatically switches to Cooling or 
Heating mode.
•  As shown by the example in the figure below, with AUTO 
cooling/heating operation, the mode changes between 
Heating and Cooling mode according to changes in the 
relationship between the current room temperature and the 
set temperature.Room temp.    Set temp.      COOL
Room temp.    Set temp.      HEAT
74
Zone A Zone B Zone C Zone C Zone B Zone A
OFF OFF Compressor
Operation mode Room temp.
Heating Cooling Cooling
ONONON More than
1 hour
Within
1 hour
Set temp.
Example
Example of operation in AUTO mode with the set room temperature 
at 74
°F(23°C).
To operate the system, press the OPERATION button, 
which is also used as the receiver, below the unit display. 
Each time this button is pressed, the OPERATION lamp 
changes color to indicate the type of operation. Select the 
desired type of operation.
8.  FUNCTIONS
8-1.  Operation Functions
47 
						

							HIGH POWERNIGHT SETBACK
Lamp colors
Timer backup
This function acts to raise the power but keeps the AC system in 
the same operating mode.
This function is set with the HIGH POWER button on the remote 
controller.
(It can be set regardless of the temperature and fan speed 
settings.)
 HIGH POWER operation from remote controller
  The unit operates at maximum output for 30 minutes, 
regardless of the desired temperature.
  The fan speed is 1 step above "High."
OPERATION lamp  When HIGH POWER operation ends, the unit operates at low 
Hz for 5 minutes, regardless of the thermostat OFF conditions.
  When in DRY mode, operation is in the cooling zone.
   Operation stops if there are no operator controls for 25 hours or 
longer after unit operation switched from OFF to ON by use of 
ON timer operation.
Frequency
MAX
0
Start EndTime
30 min. 5 min.
Setting
temperature
Press the NIGHT
SETBACK button
   When NIGHT SETBACK operation is set, the temperature and 
fan speed settings will be adjusted automatically to allow 
comfortable sleep.
   When NIGHT SETBACK operation is set, "     mark" appears on 
the remote controller. The main unit display lamp also becomes 
dimmer.
  COOL and DRY modes
When the night setback mode is selected, the air conditioner 
automatically raises the temperature setting 2°F(1°C) when 30 
minutes have passed after the selection was made, and then 
another 2°F(1°C) after another 30 minutes have passed, 
regardless of the indoor temperature when night setback was 
selected. This enables you to save energy without sacrificing 
comfort. This function is convenient when gentle cooling is 
needed.
 HEAT mode
When the night setback mode is selected, the air conditioner 
automatically lowers the temperature setting 4°F(2°C) when 30 
minutes have passed after the selection was made, and then 
another 4°F(2°C) after another 30 minutes have passed, 
regardless of the indoor temperature when night setback was 
selected. This enables you to save energy without sacrificing 
comfort. This function is convenient when gentle heating is 
needed.
OPERATION lamp Green
TIMER lamp Green
HIGH POWER lamp Green HEAT operation  Red
DRY operation  Orange
COOL operation  Green
FAN operation  Green
DEFROSTING operation  Red and Orange
 alternately
NOTE
30 min. 30 min.
Time
2°F(1°C)
Setting
temperature
Press the NIGHT
SETBACK button
30 min. 30 min.
Time
4°F(2°C)
4°F(2°C)
2°F(1°C)
48 
						

							Overload prevention during heating
During HEAT operation, the temperature of the indoor heat 
exchanger is used to control the frequency and lessen the load 
on the compressor before the protective device is activated.
Cold-air prevention during heating
Compressor discharge temperature control
During heating, the fan speed is set to "LL" (very low) or stopped.
As the temperature of the indoor heat exchanger rises, the fan 
speed is changed to the set speed.
Freeze prevention
During COOL or DRY operation, freezing is detected and 
operation is stopped when the temperature of the indoor heat 
exchanger matches the conditions below.
1.  Freeze-prevention operation is engaged when the 
temperature of the indoor heat exchanger is below 43°F(6°C).
2.  Restart after freeze-prevention operation occurs when the 
temperature of the indoor heat exchanger reaches 46°F(8°C) 
or above.
a.  Area: Automatic capacity control
b.  When Point A has been exceeded, the operation frequency is 
reduced by a certain proportion.
c.  Area: Frequency increase is prohibited.
d.  At Point B and below, overload prevention is ended and 
control is the same as in the a area.
a.  Area: Automatic capacity control
b.  When the temperature drops below Point A, the operation 
frequency is reduced by a certain proportion.
c.  Area: Frequency increase is prohibited.
d.  When the temperature reaches Point C or above, freezing 
prevention is ended and control is the same as in the a area.
*  When the temperature drops to below 36°F(2°C) 
(continuously for 2 minutes or longer), the compressor stops.
Once the freeze condition is detected, the air conditioner will 
work less than the maximum frequency until it is turned off.
Approx.
127
(53)
At stability of operation
At start of operation A
High
LL
Stopped
A
*
BC B Indoor heat exchanger
A. Control start
B. Control endSet fan speed
77
(25)86
(30)Approx. 104
(40)
abc d
abcdIndoor heat exchanger
temperature °F(°C)
Indoor heat exchanger
temperature °F(°C)
Indoor heat exchanger
temperature °F(°C)
Approx.
117
(47)
36
(2)43
(6)46
(8)
•  The fan speed is forcibly changed to "LL" beginning 30 seconds 
after the thermostat turns OFF.
•  At stability of operation refers to operation when the room 
temperature has approached the set temperature.
•  When HEAT operation starts, the indoor fan is stopped until the 
temperature of the indoor heat exchanger reaches 68°F(20°C) 
or higher, or until the room temperature reaches 59°F(15°C) or 
higher.
This function controls the operation frequency to prevent the 
compressor discharge temperature from rising more than a 
specified temperature.
a.  Area: Automatic capacity control.
b.  When the temperature rises above Point A, the operation 
frequency is reduced at a specified rate.
c.  Area: Further frequency increase is prohibited.
d.  When the temperature falls below Point B, prevention of a rise 
in frequency is released and the air conditioner operates as in 
a area.
*  The compressor will stop if the temperature of the compressor 
discharge exceeds 248°F(120°C) due to shortage of gas or 
other reason.
Approx.
214
(101)A
B
abc d
Compressor discharge temperature °F(°C)
Approx.
201
(94)
NOTE
8-2.  Protective Functions
49 
						

							This function prevents the circuit breaker or fuse from operating
 to open the circuit. This function works when electrical current 
has increased due to an increase in the cooling / heating load, 
or to a decrease in the power supply voltage. In these cases, 
operation frequency is reduced or operation is interrupted auto-
matically to control the electrical current for operation.
When the cause of the increase in electrical current is rectified, 
the system will resume operation in the original mode. •
•
Electrical current setting for COOL operation is 
used during DEFROST operation.
Cooling   Dry  Heating
Peak current cut-off trips 22.5
Hz down 14.0 15.0
(A) 
CT (Peak current cut-off control)
NOTE
Cooling   Dry  Heating
Peak current cut-off trips 17.5
Hz down 11.0 14.0
(A) 
NOTE
Heating operation
Frost sensing
Reverse-cycle defrosting operation
Defrosting Sequence
Releasing of defrosting
Outdoor fan ON
4-way valve ON
Outdoor heating exchanger temp. is over 68
°F(20°C).
Defrosting operation lasts 12 minutes (maximum).
2 minutes after it is stopped, compressor is ON.
4-way valve is ON. Outdoor fan is ON.
If the air conditioner is turned off during the defrosting 
cycle, it will continue defrosting and turn itself off after 
defrosting is completed.Compressor    1 minute after it is stopped,
            compressor is ON. 
Outdoor fan     OFF 
Indoor fan     OFF
4-way valve     OFF
Operation lamp
Reverse-Cycle Defrosting
Defrost detection and release
Repeatedly switches between red 
and orange illumination. Defrost detection occurs in either of the following cases:
The temperature of the heat exchanger remains at 
or below the L2 line for 120 minutes after the start 
of HEAT operation. 
Outdoor heat 
exchanger temp. 
Ambient temp.
0
L1 L2
Frosting area
The temperature of the heat exchanger remains at 
or below the L1 line for 3 minutes after the start of 
HEAT operation.
• •
50