Mitsubishi Electric EHGT17D-YM9ED Service Manual page 50

Code Error
Open/short of heat pump unit thermis-
U4
tors
(TH3:
(TH3, TH32, TH34, TH7 and TH8)
5105)
Abnormal if open or short is detected during
(TH7:
compressor operation.
5106)
Open detection of TH3, TH32 and TH34 is
(TH8:
inoperative for 10 seconds to 10 minutes
5110)
after compressor starting.
(TH32:
Note:
5132)
Check which unit has abnormality in its
(TH34:
thermistor by switching the mode of SW2.
5134)
(PAC-SK52ST)
Temperature of heat sink
Abnormal if TH8 detects temperature
indicated 95°C.
TH8: Thermistor <Heat sink>
U5
(4230)
Power module
Check abnormality by driving power mod-
U6
ule in case overcurrent is detected.
(4250)
(UF or UP error condition)
Too low superheat due to low discharge
temperature
Abnormal if discharge superheat is
continuously detected less than or equal
U7
to −15°C for 3 minutes even though linear
(1520)
expansion valve has minimum open pulse
after compressor starts operating for 10
minutes.
Brine pump
Abnormal if rotational frequency of the
brine pump is not detected during DC brine
U8
pump operation. Brine pump rotational
(4400)
frequency is abnormal if 500 rpm or below
or 5000 rpm or more detected continuously
for 1 minute.
To find out the details about U9 error, turn ON SW2-1, 2-2, 2-3, 2-4, 2-5 and 2-6 when U9 error occurs. (PAC-SK52ST)
Detailed
To find out the detail history (latest) about U9 error, turn ON SW2-1, 2-2 and 2-6. (PAC-SK52ST)
codes
Refer to "9-8. FUNCTION OF SWITCHES, CONNECTORS AND JUMPERS".
Overvoltage error
• Increase in DC bus voltage
to 760V
01
U9
(4220)
Undervoltage error
• Instantaneous decrease in
DC bus voltage to 350V
02
OCH722A
Cause
1. Disconnection or contact failure of connectors
Controller circuit board: TH3, TH32, TH34, TH7
Power board: CN6
2. Defective thermistor
3. Defective controller circuit board
1. Rise of ambient temperature
2. Defective thermistor
3. Defective input circuit of power circuit board
4. Failure of brine pump drive circuit
1. Decrease of power supply voltage
2. Looseness, disconnection or converse of com-
pressor wiring connection
3. Defective compressor
4. Defective controller circuit board
1. Disconnection or loose connection of discharge
temperature thermistor (TH4)
2. Defective holder of discharge temperature thermis-
tor
3. Disconnection or loose connection of linear
expansion valve's coil
4. Disconnection or loose connection of linear
expansion valve's connector
5. Defective linear expansion valve
1. Failure in the operation of the DC brine pump
2. Failure in the controller circuit board
1. Abnormal increase in power source voltage
2. Disconnection of compressor wiring
3. Defective power circuit board
4. Compressor has a ground fault.
1. Decrease in power source voltage,
instantaneous stop
2. Defective 52C drive circuit in power circuit board 2. Replace power circuit board.
3. Defective converter circuit board
4. Disconnection or loose connection of rush
current protect resistor RS
5. Defective rush current protect resistor RS
50
Action
1. Check connection of connector (TH3, TH32, TH34
TH7) on the controller circuit board.
Check connection of connector (CN6) on the
power board. Check breaking of the lead wire for
TH3, TH32, TH34, TH7, TH8.
2. Check resistance value of TH3, TH32,
TH34,TH7,TH8 or check temperature by micropro-
cessor.
3. Replace controller circuit board.
Note:
Emergency operation is available in case of ab-
normalities of TH3 and TH7.
1. Check if there is something which causes tem-
perature rise around unit.
(Upper limit of ambient temperature is 35°C.)
Turn off power, and on again to check if U5 is dis-
played within 30 minutes.
If U4 is displayed instead of U5, follow the action
to be taken for U4.
2. Check resistance value of TH8 or temperature by
microprocessor.
3. Replace power circuit board.
4. Replace controller circuit board.
1. Check facility of power supply.
2. Correct the wiring (U•V•W phase) to compressor.
3. Check compressor
4. Replace controller circuit board.
1., 2.
Check the installation conditions of discharge
temperature thermistor (TH4).
3. Check the coil of linear expansion valve.
4. Check the connection or contact of LEV-A on
controller circuit board.
5. Check linear expansion valve.
1. Check or replace the DC brine pump.
2. Check the voltage of the controller circuit board
during operation.
3. Replace the controller circuit board.
(When the failure is still indicated even after per-
forming the action 1 above.)
1. Check the field facility for the power supply.
2. Correct the wiring (U.V.W phase) to compressor. Refer
to "9-8. FUNCTION OF SWITCHES, CONNECTORS
AND JUMPERS". (Power circuit board).
3. Replace power circuit board.
4. Check compressor for electrical insulation.
Replace compressor.
1. Check the field facility for the power supply.
3. Replace converter circuit board.
4. Check RS wiring.
5. Replace RS.