Panasonic U-72MF1U9 Service Manual page 74

3. W-3WAY VRF Alarm Codes
Check
1
2
Correction
3
4
5
6
Example
7
(1) High-pressure sensor failure
Check the sensor resistance value. (Use a tester and measure the resistance between
sensor No.1 and No.3)
Resistance of less than 10k
Resistance of 10k - 200k
circuit or other trouble.
Connect a gauge to the high-pressure outlet and check for chenges in the value displayed
by the monitoring software, and for large deviation of the gauge pressure.
During heating, check whether the temperature is lower than the highest indoor-unit E1
temperature.
* The pressure detected by the high-pressure sensor is the highest pressure in the system.
Therefore during heating the converted saturation temperature will never be lower than
any indoor-unit E1 temperature. During cooling this temperature will never be lower than
the outdoor unit liquid temperature.
(2)
Failure to open the service valve, clogged tubing, valve leakage, over-charging in all of
these cases, an alarm occurs when there are rapid pressure fluctuations and tracking of
the detected pressure is poor.
Check the open/closed status of the valve.
Check for clogging of the tubing.
To check for clogging, disconnect the high-pressure sensor from the PCB and check
whether the high-pressure SW activates.
Check for valve leakage and over-charging
When valve leakage or over-charging occurs, refrigerant is likely to accumulate in the
outdoor units or indoor units, resulting in a sudden rise in pressure at start that occurs
before the refrigerant in the heat exchanger is discharged.
* The representative valves to check are the liquid valves and mechanical valves.
(3) Outdoor unit PCB failure
The check items are the same as for a high-pressure sensor malfunction.
A normal PCB is needed to determine whether the problem is a PCB failure or a pressure
sensor malfunction. If an abnormality was found at the check items for a high-pressure
sensor malfunction, first try replacing the PCB and check again.
Trouble is corrected: Outdoor unit PCB failure
Trouble is not corrected: High-pressure sensor malfunction
(1) Replace the high-pressure sensor.
Caution: Because the high-pressure sensor connection employs a Schrader-type valve, it can
be removed and replaced. However, the high-pressure sensor can be easily
damaged by high voltage; therefore use sufficient caution with regard to static
electricity.
(2) Replace the PCB.
(3) Correct the locations of problems in the refrigeration cycle.
Correct locations where clogging or leakage has occurred.
In the case of over-charging, recover refrigerant. (Adjust the amount of refrigerant).
* Guide for over-charging
Be sure to connect the gauge to the high-pressure pressure outlet when checking for over-
charging.
During cooling: The following does not apply when outdoor air temperature is low or when fan
speed is controlled. When both compressor 1 and compressor 2 are
operating, and the fan mode is 14 (maximum fan speed), then the high
pressure saturation temperature should be approximately 15°C above the
outdoor air temperature. If it is 5°C or more above this level, then it is
possible that over-charging may have occurred.
During heating: There is an indoor unit where refrigerant flow is poor (E1 temperature and
discharge temperature are low), and the mechanical valve of that unit is
opened to 300 pulses or more, and the E1 temperature is close to room
temperature. However be aware that this kind of data results often when
there is a height difference between indoor units. Reducing the amount of
refrigerant will improve the refrigerant flow, however reducing it too much will
increase the likelihood of alarms related to low oil level (scroll-side), the low
pressure SW, and discharge temperature. Use caution.
This alarm may result when the service valve is closed or when valve leakage (particularly from
the mechanical valve) occurs.
indicates a short circuit or other trouble.
is normal. Resistance of more than 200k
3 - 12
Trouble Diagnosis
indicates an open