Panasonic Cu 3ks19nbucu 4ksxxnbu Technical Service Manual

							Outdoor Unit  : CU-4KS31NBU
Indoor Unit  : CS-MKS9NB4U × 4
Power Supply  :  230V Single Phase 60Hz
 RATING CAPACITY:    28,600 BTU/h       AIR FLOW RATE: 883 CFM
INDOOR OUTDOOR
 ENT. TEMP. 
oF (oC)     AMBIENT TEMP. oF (oC)
W B DB 15 25 35 45 55
(-9.4) (-3.9) (1.7) (7.2) (12.8)
TC 28,890 28,790 28,810 28,990 28,870
72 (22.2) SHC 22,560 28,790 22,560 22,730 22,560
59 76 (24.4) SHC 25,980 28,790 25,810 25,980 25,980
(15.0) 80 (26.7) SHC 28,890 28,790 28,810 28,990 28,870
84 (28.9) SHC 28,890 28,790 28,810 28,990 28,870
88 (31.1) SHC 28,890 28,790 28,810 28,990 28,870
TC 29,170 29,150 29,320 29,660 29,650
72 (22.2) SHC 18,440 29,150 18,440 18,610 18,610
63 76 (24.4) SHC 21,700 29,150 21,700 21,870 21,870
(17.2) 80 (26.7) SHC 25,130 29,150 25,130 25,300 25,300
84 (28.9) SHC 28,390 29,150 28,390 28,560 28,560
88 (31.1) SHC 29,170 29,150 29,320 29,660 29,650
TC 29,210 29,310 29,650 30,210 30,330
72 (22.2) SHC 14,160 29,310 14,330 14,500 14,500
67 76 (24.4) SHC 17,410 29,310 17,580 17,760 17,930
(19.4) 80 (26.7) SHC 20,840 29,310 21,010 21,180 21,360
84 (28.9) SHC 24,100 29,310 24,270 24,440 24,610
88 (31.1) SHC 27,360 29,310 27,530 27,870 27,870
TC 28,970 29,200 29,760 30,580 30,860
72 (22.2) SHC 9,700 29,200 9,870 10,210 10,210
71 76 (24.4) SHC 12,960 29,200 13,130 13,470 13,640
(21.7) 80 (26.7) SHC 16,380 29,200 16,560 16,900 17,070
84 (28.9) SHC 19,640 29,200 19,810 20,160 20,330
88 (31.1) SHC 22,900 29,200 23,240 23,410 23,580
TC 28,440 28,820 29,620 30,720 31,170
75 76 (24.4) SHC 8,500 28,820 9,010 9,360 9,530
(23.9) 80 (26.7) SHC 11,930 28,820 12,440 12,780 12,960
84 (28.9) SHC 15,360 28,820 15,700 16,040 16,210
88 (31.1) SHC 18,610 28,820 18,960 19,300 19,470
NOTE
< Cooling Capacity (Low Ambient) >
TC : Total Cooling Capacity (BTU/h)   SHC : Sensible Heat Capacity (BTU/h)
1.
2. Above data represents the value when the operation frequency of a compressor is fixed.Above data does not take Freeze Prevention Protection during cooling operation into account. 
For this reason, the value may vary from the actual cooling characteristics.
61 
						

							6.  ELECTRICAL DATA
6-1.  Electric Wiring Diagrams
Outdoor Unit CU-3KS19NBU
8FA2-5251-11800-1
62 
						

							Outdoor Unit CU-4KS24NBU
8FA2-5251-11600-1
63 
						

							Outdoor Unit CU-4KS31NBU
8FA2-5251-11400-1
64 
						

							7.  FUNCTIONS
7-1.  Explanation of Functions
The numerical values such as temperature, frequency, time and current in parentheses are an example 
of CU-4KS31NBU and the values are different from the other models.
Control/conditions
INITIAL
Breaker is ON. Power is supplied to the indoor and outdoor unit 
control circuits, however the unit remains stopped.
Positioning of the outdoor unit electric expansion 
valve is performed.
The ON/OFF operation 
button on the remote 
controller is pressed.If automatic operation mode has been selected 
with the remote controller, operation begins in 
SENSOR DRY, or COOL mode depending 
on the room temperature and 
outdoor temperature at the time operation starts.
Depending on the operational mode, refer to the SENSOR DRY, or COOL item.This applies in the case of automatic 
COOL operation.
Unit operation Explanation
NOTE
65 
						

							Control/conditions
COOL
The ON/OFF operation 
button on the remote 
controller is pressed.
The room temperature 
has reached the 
desired temperature.The outdoor unit does not operate for 3 minutes 
even after the breaker is turned ON.
This is in order to stabilize the return of oil to the 
compressor. The outdoor unit starts.
(Compressor and the outdoor fan start.)
When the frequency reaches    Hz, 
frequency increases are stopped for a period 
of    seconds. (Refer to Table 1.)
If the indoor and outdoor temperatures are high, 
the current peak cut-off activates, stopping 
any increases in frequency. The frequency then increases.
Operating frequency is stabilized in order to 
maintain a comfortable environment. The indoor temperature and the desired 
temperature are approximately equal.
The thermostat turns 
ON again. After 3 minutes, the outdoor unit begins operating 
automatically.
During these 3 minutes, a pressure balance is 
achieved, allowing the compressor to start 
more easily. After the thermostat turns ON again, the 
outdoor unit will not operate for 3 minutes, 
even if the room temperature increases 
above the desired temperature.
Operation is restarted 
within 4 hours (only when 
AUTO mode is selected 
with the remote 
controller).Within 4 hours after operation was stopped, it is 
assumed that there has been no significant 
change in the indoor and outdoor temperatures, 
and the previous conditions (COOL) are stored. Starts operating in the same operating mode 
(COOL) and with the same temperature 
settings as before operation was stopped.
Operation starts after 4 
hours or more have 
passed.New operating mode is determined based on 
the temperature conditions at the time the 
ON/OFF operation button is pressed.
Stop All indicator lamps turn OFF. The indoor and 
outdoor units stop.
Freeze prevention In order to protect against freezing, the 
compressor stops temporarily, until the 
temperature of the indoor heat exchanger has 
risen.
The thermostat turns
OFF.The outdoor unit stops. (It does not stop if the
thermostart for another indoor unit is ON.)
Unit operation Explanation
The operation lamp illuminates.
The indoor fan operates at the set fan speed.
The outdoor unit stops.
When the temperature of the indoor heat 
exchanger drops to approximately 35.6 °F 
or below, the compressor turns OFF, the 
outdoor fan turns OFF, and the indoor fan 
continues operating with no changes.
Approximately 3 minutes later, if the 
temperature of the indoor heat exchanger 
is adove 46.4 °F, the system returns to its 
original conditions.
The frequency is increased at the rate of 0.5 
Hz every 1 seconds.
Frequency control
    (Hz)
(25) Hz
(35) Hz
(45) Hz
(55) HzOutdoor air temperature is below 32 °F.
(120) seconds
(60) seconds
(60) seconds
(180) seconds
Table 1
     (senconds)
Outdoor air temperature is 32 °F or higher.
(60) seconds
(30) seconds
(30) seconds
(90) seconds
66 
						

							Control/conditions
SENSOR 
DRY
(1/f fluctuation fan)
The ON/OFF operation 
button on the remote 
controller is pressed.The outdoor unit does not operate for 3 minutes 
even after the breaker is turned ON.
This is in order to stabilize the return of oil to the 
compressor. The outdoor unit starts.
(Compressor and the outdoor fan start.)
When the frequency reaches    Hz, 
frequency increases are stopped for a period 
of    seconds. (Refer to Table 1.)
DRY B operation
If the indoor and outdoor temperatures are high, 
the current peak cut-off activates, stopping 
any increases in frequency. The frequency then increases.
Unit operation Explanation
The operation lamp illuminates.
The indoor fan operates at the set fan speed.
The outdoor unit stops.
The room temperature 
reaches the desired 
temperature, and there 
is no need for further 
cooling.Operating frequency is stabilized in order to 
maintain a comfortable environment.
The room temperature is 
59 °F or higher, and is 
slightly too cold.
The compressor operates on a 3-minutes ON, 
6-minutes OFF cycle, to prevent the room 
temperature from dropping too much. DRY operation starts
DRY A operation
The room temperature is 
below 59 °F.When monitoring operation begins, the 
compressor stops, and the indoor fan operates at 
"LL" (very low) speed. Monitoring operation begins.
The indoor fan changes between "Low" 
and "LL" (very low) over a 6-minute cycle. 
This is 1/f fluctuation fan operation. 
(Refer to Fig. 1.)
The indoor fan changes between "Low" 
and "LL" (very low) over a 6-minute cycle. 
This is 1/f fluctuation fan operation.    
After appoximately 3 minutes, the 
compressor turns OFF, the outdoor fan 
turns OFF, and the indoor fan turns OFF.
After approximately 6 minutes, the 
conditions return to (1). (1)
(2)
(3)
The frequency is increased at the rate of 0.5 
Hz every 1 seconds.
Operates to effectively dehumidify the air while 
not excessively reducing the indoor 
temperature.
The indoor unit operates at 1/f fluctuation fan 
operation, at a fan speed that does not cause 
a chilly feeling.
1/f fluctuation fan
250
200
6-minute cycle
Fig. 1
150
100 (Step)
50
0
67 
						

							< Low Ambient Cooling Operation >
When the mode is switched from cooling opration to low ambient cooling operation,
the compressor is stopped for 150 seconds temporarily.
Outdoor fan speed [ rpm ]
Outdoor air temperature32 °F ( °C )
When the mode has been switched to low ambient cooling operation,
the outdoor fan speed is lowered as the outdoor air temperature falls.
When the outdoor air temperature reaches 57.2 °F (14 °C ) or less during the cooling operation,
the operation mode is switched to low ambient cooling operation.
The following protective actions are available to prevent the compressor from operating
with abnormal loads.
At that time, they initiate thermo-off ( stopping the outdoor unit ) of the air conditioner.
When the outdoor air temperature reaches 62.6 °F (17 °C ) or more during the low ambient
cooling operation, the operation mode is switched to cooling operation.
8.6 (-13)14 (-10)
Compressor
Indoor fanOFF
ON ON Outdoor air temp.
 °F ( °C )
ON
68 
						

							7-2.  Protective Functions
The numerical values such as temperature, frequency, time and current in parentheses are an example 
of CU-4KS31NBU and the values are different from the other models.NOTE
7-2-1.  Current Control
The operating current may rise as a result of causes including increasing cooling loads or decreases in power 
voltage. In these cases, the operating frequency is automatically reduced, or operation is stopped, in order to control 
the operating current so that it is (20 A) or less.
The operating frequency is reduced automatically, or operation is stopped, in order to control the operating 
current so that it is at or below the values shown in the table below.
(20A) Power breakers and fuses will not be tripped.
Operation can continue during this period with somewhat reduced cooling capacity.
Operation at normal capacity is restored when the cause of the current rise is eliminated.
Description of function
•
•
•
Example of operation for cooling
Frequency
Frequency CurrentStops operation
Approx.3 minutesPower Point C
Point B
Point A (20A)
(17A)
(16.6A)
Target
frequency
Operates at the target frequency at Point A and below.
Stops increases to the frequency between Points A and B.
Reduces the frequency by 1 Hz per 0.5 seconds when Point B is exceeded.
Stops operation, and restarts it appoximately 3 minutes later, if Point C is exceeded.
(May operate when sudden voltage fluctuations occur.    Indicates trouble.) •
•
•
•
As a result:
(1) Automatic frequency control
COOL
(20.0)
(17.0) Point C (peak cut trip)
Point B (Hz reduction)
Point A (Hz increase prohibit) (16.6)
69 
						

							Current(A)
Frequency (Hz) Trip
Hz reduction
Hz increase
prohibitHz reduction
Hz increase prohibit
Hz reduction
Hz increase prohibit
(16)
(15.6)
0
(30)Example of operation during cooling
The operating frequency upper limits shown in the figure below are established for frequency reduction and 
increase-prohibit.
(2) Current control
(230)
(223)
(212)Trip
5Hz every 30 sec. reduction
2Hz every 30 sec. reduction
No controlIncrease
prohibit range
(Hz reduction) (°F)
Compressor discharge temperature(194)
Within the increase-prohibit range, the range changes 
to the Hz reduction range (2 Hz every 30 seconds) if 
the compressor temperature rises by 4 °F. * Operation starts at (8 Hz), and the start current is less than the normal operating  current. This prevents the flickering 
of fluorescent lights or television screens that occurs when ordinary A/C units start.
7-2-2.  Low Start Current
To protect the compressor coil from overheating, the operating frequency is controlled based on the compressor 
discharge temperature.
7-2-3.  Compressor Temperature Control
70