Mitsubishi Electric EHWT17D-MHEDW, Data Book

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Code Error Cause Action
U2
(1102)
High discharge temperature
(1) Abnormal if TH4 exceeds
125°C or 110°C continuously
for 5 minutes.
(2) Abnormal if discharge super-
heat (Heating: TH4−T63HS)
exceeds 70°C continuously for
10 minutes.
TH4: Thermistor <Discharge>
High comp. surface temperature
Abnormal if TH33 exceeds 125°C.
In the case of high comp. surface
temperature error, compressor
does not restart unless the ther-
mistor (TH33) becomes less than
95°C.
TH33: Thermistor <Comp. sur-
face>
Overheated compressor operation
caused by shortage of refrigerant
Check intake superheat.
Check leakage of refrigerant.
Charge additional refrigerant.
Defective thermistor Turn the power off and check if U3 is
displayed when the power is turned
on again.
When U3 is displayed, refer to 'Judg-
ment and action' for U3.
Defective C.B.
Defective action of linear expansion
valve
Check linear expansion valve.
Clogging with foreign objects in re-
frigerant circuit
Note:
Clogging occur in the parts which be-
come below freezing point when water
enters in refrigerant circuit.
After recovering refrigerant, remove
water from entire refrigerant circuit
under vacuum more than 1 hour.
In the case of the unit does not re-
start:
Detection temp. of thermistor (TH33)
≥ 95°C
U3
(5104)
Open/short circuit of heat pump
unit temperature thermistor
(TH4, TH33)
Abnormal if open (3°C or less) or
short (217°C or more) is detected
during compressor operation.
(Detection is inoperative for 10
minutes of compressor starting
process and for 10 minutes after
and during defrosting.)
TH4: Thermistor <Discharge>
TH33: Thermistor <Comp. sur-
face>
Disconnection or contact failure of
connectors (TH4, TH33) on the C.B.
Check connection of connector (TH4,
TH33) on the C.B.
Check breaking of the lead wire for
TH4, TH33.
Defective thermistor Check resistance value of TH4, TH33
or temperature by microprocessor.
Defective C.B. Replace C.B.
U4
(TH3:
5105)
(TH7:
5106)
(TH8:
5110)
(TH32:
5132)
(TH34:
5134)
Open/short of heat pump unit
thermistors
(TH3, TH32, TH34, TH7 and TH8)
Abnormal if open or short is detected
during compressor operation.
Open detection of TH3, TH32 and
TH34 is inoperative for 10 seconds
to 10 minutes after compressor
starting.
Note:
Check which unit has abnormality
in its thermistor by switching the
mode of SW2. (PAC-SK52ST)
Disconnection or contact failure of
connectors
C.B.: TH3, TH32, TH34, TH7
Power board: CN6
Check connection of connector (TH3,
TH32, TH34 TH7) on the C.B.
Check connection of connector (CN6)
on the power board. Check breaking
of the lead wire for TH3, TH32, TH34,
TH7, TH8.
Defective thermistor Check resistance value of TH3, TH32,
TH34,TH7,TH8 or check temperature
by microprocessor.
Defective C.B. Replace C.B.
Note:
Emergency operation is available in
case of abnormalities of TH3 and TH7.
U5
(4230)
Temperature of heat sink
Abnormal if TH8 detects tempera-
ture indicated 95°C.
TH8: Thermistor <Heat sink>
Rise of ambient temperature Check if there is something which
causes temperature rise around unit.
(Upper limit of ambient temperature is
35°C.)
Turn off power, and on again to check
if U5 is displayed within 30 minutes.
If U4 is displayed instead of U5, fol-
low the action to be taken for U4.
Defective thermistor Check resistance value of TH8 or
temperature by microprocessor.
Defective input circuit of power cir-
cuit board
Replace power circuit board.
Failure of brine pump drive circuit Replace C.B.
U6
(4250)
Power module
Check abnormality by driving
power module in case overcurrent
is detected.
(UF or UP error condition)
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 C.B. Replace C.B.
B-261
Water to Water Heat Pump (WTW)
7
Cylinder
unit/
Hydrobox/GSHP/WTW
Cylinder
unit/
Hydrobox/GSHP/WTW