Panasonic 2WAY Multi - P18 Bypass Valve Error

IV–94
P18 Bypass Valve Error

Error detection method
• A warning is output if it is determined that the outdoor unit needs a bypass valve inspection.
• In practical terms, what happens is that each time there is a small difference ( P ≤ 0.1 MPa) between the
high and low pressure ( P = high pressure - low pressure) 90 seconds after stopping the engine stops, a
suspected error counter increments, and the data is recorded as “pre-trip” warning history data. After the
counter reaches 5, a warning is output on the next complete combustion startup.

Understanding the warning history
The latest P18 data in the warning history is issued immediately after a complete combustion startup. It is not
the data used for detecting the error. If a pre-trip error was detected (when the suspected error counter reaches 5),
that data is the next more recent P18 data.

Troubleshooting
1
Bypass
valve
inspection
1-1
● Bypass valve inspection

During operation, use the No. 4 test mode “v_close” (close
valve) to close the bypass valve (step 0). Check whether
refrigerant is not leaking on entering the bypass.
OK 1-2
NG
Replace the bypass
valve unit
1-2
● Bypass valve inspection

After completing the above inspections, stop the engine and
use No.4 test mode “v_open” (open valve) to open the bypass
to check that the bypass valve operates normally despite the
fl uctuations in tube temperature around the bypass valve.
OK 2-1
NG 1-3
1-3
● Outdoor main board inspection
Is there approximately 12 V of pressure at bypass valve output
ports 5 (+) and 1 to 4 (-) when the power is on?
Yes 1-4
No
Replace outdoor main
board
1-4
● Electric valve coil inspection
Are the resistance values for electric valve connectors 5 and
1 to 4 about 40 Ω?
Yes
Replace the bypass
valve unit
No
Replace the bypass
valve coil
2
Four-way
valve
Inspect
outdoor
solenoid
valves
2-1 Is the outdoor unit a 3-WAY MULTI-device?
Yes 2-3
No 2-2
2-2 Is the four-way valve free from leakage?
OK 3-1
NG
Replace the four-way
valve
2-3
Are the outdoor solenoid valves (discharge valves 1 and 2,
and suction valves 1 and 2) free from leakage?
* Suction valve 1 closes when current fl ows through it (other
solenoid valve remain open)
OK 3-1
NG
Replace the solenoid
valve.
3
Liquid valve
inspection
3-1
● Liquid valve inspection

Any refrigerant leaks past the liquid valve when the liquid
valve is completely closed (step 0)?
OK 4-1
NG
Replace the liquid valve
unit
4
Expansion
valve
inspection
4-1
Is the operation mode heating?
* Note: If you are operating with a 3WAY MULTI, try 4-2 and
4-3 before shutting down the engine as this might be
due to cooling and heating mixed operation.
Yes 4 -2
No 4-3
4-2
● Outdoor expansion valve inspection
Check that there are no refrigerant leaks past the outdoor
expansion valve when the engine is stopped in heating mode.
OK 5-1
NG
Replace the outdoor
expansion valve unit
4-3
● Indoor electric valve inspection
Stop the indoor unit during cooling operation (multiple indoor
unit operation, indoor electric valve opening = 20 steps) and
check to make sure there is no coolant leakage beyond the
indoor electric valve.
OK 5-1
NG
Replace indoor electric
valve unit
5
Pressure
sensor
inspection
5-1
Pressure sensor inspection (refer to the section on F16 for the
inspection procedure)
OK
Replace outdoor main
board
NG Repair
● For work procedure for replacing outdoor main board, see “5. Reference Document”.
GHPtroubleshooting.indbIV‒94GHPtroubleshooting.indbIV‒94 2012/11/2611:20:142012/11/2611:20:14