Mitsubishi Electric PQHY-P72ZLMU-A Service Handbook page 256

[ IX Troubleshooting ]
1. Error Code
1302
High pressure fault 1 (Heat source unit)
2. Error definition and error detection method
1) If the pressure of 3.78MPa [548psi] or higher is detected by the pressure sensor during operation (the first detection), the heat
source stops once, turns to antirestart mode for 3 minutes, and restarts after 3 minutes automatically.
2) If the pressure of 3.78MPa [548psi] or higher is detected by the pressure sensor again (the second detection) within 30 min-
utes after the first stop of the heat source unit, the heat source unit stops once, turns to anti-restart mode for 3 minutes, and
restarts after 3 minutes automatically.
3) If the pressure of 3.87MPa [561psi] or higher is detected by the pressure sensor (the third detection) within 30 minutes of the
second stop of the heat source unit, the heat source unit will make an error stop, and the error code "1302" will be displayed.
4) If the pressure of 3.78MPa [548psi] or higher is detected more than 30 minutes after the stop of the heat source unit, the de-
tection is regarded as the first detection, and the operation described in step 1 above will start.
5) For 30 minutes after the stop of the heat source unit, preliminary errors will be displayed on the LED display.
6) The heat source unit makes an error stop immediately when not only the pressure sensor but also the pressure switch detects
+0,-0.15 +0,-22
4.15 MPa [601
3. Cause, check method and remedy
(1) Indoor unit LEV actuation failure
(2) BC controller LEV malfunction Heating only or heating main :
Indoor LEV 3
(3) BC controller SVM1 and 2 malfunction
Cooling only
(4) BC controller SVA and SVC malfunction
Cooling only or cooling main
(5) BC controller SVB malfunction
(6) Heat source unit LEV7 actuation failure Cooling
(7) Port address setting error.
(8) Refrigerant service valve actuation failure
(9) Short cycle on the indoor unit side
(10) Clogged filter on the indoor unit
(11) Reduced air flow due to dirty fan on the indoor unit fan
(12) Dirty heat exchanger of the indoor unit
(13) Insufficient heat source water flow
(14) Heat source water supply cutoff
(15) Dirty or clogged water heat exchanger
Items (13) through (15) above reduce the condensing capabil-
ity of the unit, resulting in high-pressure rise during heating op-
eration.
(16) Solenoid valve (SV1a) malfunction
The by-pass valve (SV1a) can not control rise in high pressure.
(17) Thermistor failure (TH3, TH7)
(18) Pressure sensor failure
(19) Failure of the thermistor input circuit and pressure sensor input
circuit on the controller board
(20) Thermistor mounting problem (TH3, TH7)
(21) Disconnected male connector on the pressure switch (63H1) or
disconnected wire
(22) Voltage drop caused by unstable power supply voltage
HWE15150
psi]
Cause
Heating
Heating only or heating main
- 247 -
Check method and remedy
Perform a heating operation and check the op-
eration.
Cooling: LEV on the indoor unit
Heat source unit LEV7
BC controller LEV1,2,3
BC controller SVM1,1b,2,2b
BC controller SVA
Heating: LEV on the indoor unit
Heat source unit LEV7
BC controller LEV3
BC controller SVM2,2b
BC controller SVB
Refer to the page on troubleshooting for LEV
and solenoid valve.
Confirm the port address of the indoor unit.
Confirm that the refrigerant service valve is fully
Check the indoor units for problems and correct
them, if any.
Check the water heat exchanger for clogging.
Check the heat source water circulation pump.
Refer to the section on troubleshooting the so-
lenoid valve.
Check the thermistor resistor.
Refer to the page on the troubleshooting of the
high pressure sensor.
Check the sensor temperature/pressure on the
LED monitor.
Check the sensor temperature/pressure on the
LED monitor.
Check the input voltage at the power supply ter-
minal TB1.
GB