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7
Water to Water Heat Pump (WTW)
Code
Error
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>
U2
(1102)
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>
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.
U3
(Detection is inoperative for 10
(5104)
minutes of compressor starting
process and for 10 minutes after
and during defrosting.)
TH4: Thermistor <Discharge>
TH33: Thermistor <Comp. sur-
face>
Open/short of heat pump unit
thermistors
U4
(TH3, TH32, TH34, TH7 and TH8)
(TH3:
Abnormal if open or short is detected
5105)
during compressor operation.
(TH7:
Open detection of TH3, TH32 and
5106)
TH34 is inoperative for 10 seconds
(TH8:
to 10 minutes after compressor
5110)
starting.
(TH32:
5132)
Note:
(TH34:
Check which unit has abnormality
5134)
in its thermistor by switching the
mode of SW2. (PAC-SK52ST)
Temperature of heat sink
Abnormal if TH8 detects tempera-
ture indicated 95°C.
TH8: Thermistor <Heat sink>
U5
(4230)
Power module
Check abnormality by driving
U6
power module in case overcurrent
(4250)
is detected.
(UF or UP error condition)
Cause
Overheated compressor operation
caused by shortage of refrigerant
Defective thermistor
Defective C.B.
Defective action of 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.
In the case of the unit does not re-
start:
Detection temp. of thermistor (TH33)
≥ 95°C
Disconnection or contact failure of
connectors (TH4, TH33) on the C.B.
Defective thermistor
Defective C.B.
Disconnection or contact failure of
connectors
C.B.: TH3, TH32, TH34, TH7
Power board: CN6
Defective thermistor
Defective C.B.
Rise of ambient temperature
Defective thermistor
Defective input circuit of power cir-
cuit board
Failure of brine pump drive circuit
Decrease of power supply voltage
Looseness, disconnection or converse
of compressor wiring connection
Defective compressor
Defective C.B.
Action
Check intake superheat.
Check leakage of refrigerant.
Charge additional refrigerant.
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.
Check linear expansion valve.
After recovering refrigerant, remove
water from entire refrigerant circuit
under vacuum more than 1 hour.
Check connection of connector (TH4,
TH33) on the C.B.
Check breaking of the lead wire for
TH4, TH33.
Check resistance value of TH4, TH33
or temperature by microprocessor.
Replace C.B.
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.
Check resistance value of TH3, TH32,
TH34,TH7,TH8 or check temperature
by microprocessor.
Replace C.B.
Note:
Emergency operation is available in
case of abnormalities of TH3 and TH7.
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.
Check resistance value of TH8 or
temperature by microprocessor.
Replace power circuit board.
Replace C.B.
Check facility of power supply.
Correct the wiring (U•V•W phase) to
compressor.
Check compressor
Replace C.B.
B-261
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