Panasonic Cu 3ke19nbucu Technical Service Manual

7.  FUNCTIONS
7-1.  Explanation of Functions
The numerical values such as temperature, frequency, time and current in parentheses are an example 
of CU-4KE31NBU 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...

Control/conditions
HEAT
When defrost operation 
begins, frost has formed 
on the outdoor unit 
(when the ambient air 
temperature is low).Defrost operation begins based on outdoor 
heat exchanger temperature and outdoor 
air temperature conditions.
Non-stop defrost (Refer to Fig. 1)
1. After HEAT operation begins, the temperature 
of the outdoor heat exchanger is at or below the 
L1 line for 35 minutes.
(If outdoor air temperature is less than 26.6 °F,
the time is 48 minutes) 
2. After HEAT operation...

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 2.)
If the indoor and...

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 2.)
DRY B operation
If the indoor and outdoor temperatures...

1/f fluctuation fan
250
200
6-minute cycle
Fig. 2
150
100 (Step)
50
0
75 

< 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...

7-2.  Protective Functions
7-2-1.  Defrost Detection and Release
(2) Clean defrost
If all indoor units are stopped during HEAT operation, and frost is detected at the L1 line, and the 
conditions for defrost are met, then defrost operation occurs, and the unit stops after defrost is completed. (1) Non-stop defrosting
Heating operation
NOTEDefrost does not occur during HIGH POWER operation.
If other stopped indoor units are started during defrost operation, they begin operating in 
defrost mode.
Frost...

7-2-2.  Current Control
The operating current may rise as a result of causes including increasing heating or 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)...

7-2-5.  Control at HEAT Start-up
If HEAT operation is started when the outdoor air temperature is 59 °F or below, the unit operates at the HEAT start-up 
frequency (70 Hz or above).
Reset conditions
The compressor frequency exceeds the start-up frequency of (70 Hz).
The compressor thermostat is OFF.
Frequency reduction for indoor high-load control has occurred.
The outdoor air temperature is above 59 °F.
The main-unit switch on one or more indoor units is set to TEST run. (1)
(2)
(3)
(4)
(5)
(230)
(223)...

8.  TROUBLESHOOTING (BEFORE CALLING FOR SERVICE)
8-1.  Precautions before Performing Inspection or Repair
Both the indoor unit and outdoor unit include electronic control circuits. 
Be sure to pay attention to the following before inspecting or repairing the 
outdoor-side electronic circuits.
High-capacity electrolytic capacitors are used inside the outdoor unit controller (inverter). They retain an 
electrical charge (charging voltage DC 311 V) even after the power is turned OFF, and some time is...