Mitsubishi Electric EHWT17D-MHEDW, Data Book

Page: 65 / 131

Code Error Cause Action
U7
(1502)
Too low superheat due to low
discharge temperature
Abnormal if discharge superheat is
continuously detected less than or
equal to −15°C for 3 minutes even
though linear expansion valve
has minimum open pulse after
compressor starts operating for 10
minutes.
Disconnection or loose connection
of discharge temperature thermistor
(TH4)
Check the installation conditions of
discharge temperature thermistor
(TH4).
Defective holder of discharge tempera-
ture thermistor
Disconnection or loose connection of
linear expansion valve’s coil
Check the coil of linear expansion valve.
Disconnection or loose connection of
linear expansion valve’s connector
Check the connection or contact of
LEV-A on C.B.
Defective linear expansion valve Check linear expansion valve.
U8
(4400)
Brine pump
Abnormal if rotational frequency
of the brine pump is not detected
during DC brine pump operation.
Brine pump rotational frequency
is abnormal if 500 rpm or below or
5000 rpm or more detected con-
tinuously for 1 minute.
Failure in the operation of the DC brine
pump
Check or replace the DC brine pump.
Failure in the C.B. Check the voltage of the C.B. during
operation.
Replace the C.B.
(When the failure is still indicated
even after performing the action
above.)
U9
(4220)
Abnormal voltage error
See service handbook.
See service handbook. See service handbook.
UE
(1302)
Abnormal pressure of 63HS
Abnormal if 63HS detects 0.1 MPa
or less.
Detection is inoperative for 3 min-
utes after compressor starting and
3 minutes after and during defrost-
ing.
63HS: High pressure sensor
Disconnection or contact failure of
connector (63HS) on the C.B.
Check connection of connector
(63HS) on the C.B.
Check breaking of the lead wire for
63HS.
Defective pressure sensor Check pressure by microprocessor.
(Pressure sensor/ 63HS)
Defective C.B. Replace C.B.
UL
(1300)
Low pressure
Abnormal if TH33-TH4 exceeds
20°C and TH33 exceeds 80°C dur-
ing compressor operation.
Defective linear expansion valve. Check linear expansion valve.
Defective C.B. Replace C.B.
UF
(4100)
Compressor overcurrent inter-
ruption
(When compressor locked)
Abnormal if overcurrent of DC bus
or compressor is detected within
30 seconds after compressor
starts operating.
Decrease of power supply voltage Check facility of power supply.
Looseness, disconnection or converse
of compressor wiring connection
Correct the wiring (U•V•W phase) to
compressor.
Defective compressor Check compressor.
Defective power board Replace power circuit board.
UH
(5300)
Current sensor error or input
current error
• Abnormal if current sensor de-
tects –1.0A to 1.0A during com-
pressor operation. (This error is
ignored in case of test run mode.)
• Abnormal if 40A of input current
is detected or 37A or more of
input current is detected for 10
seconds continuously.
Disconnection of compressor wiring Correct the wiring (U•V•W phase) to
compressor.
Defective circuit of current sensor on
power circuit board
Replace power circuit board.
Decrease of power supply voltage Check the facility of power supply.
Leakage or shortage of refrigerant Check leakage of refrigerant.
UA
(2511)
Low brine flow rate (flow switch
operated)
Abnormal if flow switch is operated
(under 5.5L/min) during compres-
sor operation.
Valve or PICV of ambient loop circuit is
closed during operation.
Check valve or PICV.
Active SW6-4 on FTC, if TBI.4 7-8 is
connected.
Disconnection or loose connection of
connector (63L) on C.B.
- Turn the power off and on again
to check if F3 is displayed on
restarting.
If F3 is displayed, follow the F3
processingdirection.
Disconnection or loose connection of
63L
Defective C.B.
Misconnection of Water/Brine pipe.
Check Water/Brine pipe connection.
UP
(4210)
Compressor overcurrent inter-
ruption
Abnormal if overcurrent DC bus
or compressor is detected after
compressor starts operating for 30
seconds.
See service handbook. See service handbook.
B-262
Water to Water Heat Pump (WTW)
7
Cylinder
unit/
Hydrobox/GSHP/WTW