Mitsubishi EHPT20X-MHCW, Service Manual

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64
Error code Title and display conditions Possible Cause Diagnosis and action
P1/P2/L5/LD Indoor unit temperature thermistor failure
Note: The thermistors subject to failure can be
checked in “Request code: 567” in
“Running information.
<DHW/Heating/Cooling/LP/FS/OS>
Error code displayed when thermistor is at open or
short (see table).
Exceptions
Error code will not be displayed for TH2; During
defrost and for 10 minutes after defrost operation.
Error code
Thermistor
Open detection Short detection
Symbol Name
P1 TH1A/TH1B Room temperature thermistor −39ºC or below 88.5ºC or above
P2 TH2 Liquid temperature thermistor −39ºC or below 88.5ºC or above
L5
THW1 Flow water temperature thermistor −39ºC or below 88.5ºC or above
THW2 Return water temperature thermistor −39ºC or below 88.5ºC or above
THW5 Tank water temperature thermistor −39ºC or below 88.5ºC or above
THW6 Zone1 flow water temperature thermistor −39ºC or below 88.5ºC or above
THW7 Zone1 return water temperature thermistor −39ºC or below 88.5ºC or above
THW8 Zone2 flow water temperature thermistor −39ºC or below 88.5ºC or above
THW9 Zone2 return water temperature thermistor −39ºC or below 88.5ºC or above
LD
THWB1 Boiler flow water temperature thermistor −40ºC or below 140ºC or above
THWB2 Boiler return water temperature thermistor −40ºC or below 140ºC or above
1. Connector/terminal wire has become
detached or loose wiring.
1. Visually check the terminals and connec-
tions and reattaches appropriate.
2. Thermistor fault 2. Check resistance of thermistor against
table in "10-6. Checking Component Parts'
Function".
Compare FTC detected temperature to
hand held detector.
3. FTC board failure 3. Replace board.
4. The thermistor on the wireless remote
controller or the main remote control-
ler may be defective. (when Room
temp. is chosen for the Heating opera -
tion and when Main remote controller
or Room RC 1-8 is chosen for the
Room Sensor setting in the Initial
setting)
4. Replace wireless remote controller or main
remote controller.
5. Incorrect setting of the DIP switch(es) 5. Check the DIP switch setting(s).
L6 Circulation water freeze protection
<DHW/Heating/Cooling/LP/FS/OS>
Error code displayed when THW1 detects a
temp. ≤ 1ºC for 10 consecutive seconds or
THW2 detects a temp. ≤ 3ºC for 10 consecutive
seconds.
Exception
Error code will not be displayed if;
FS function is disabled,
For 10 minutes after water circulation pump1 is
switched on.
1. Insufficient system head 1. Refer to table in "10-6. Checking Compo -
nent Parts' Function" to determine if system
pump meets requirements.
If more head required either add a pump of
the same size or replace existing pump with
capacity model.
See "11. DISASSEMBLY PROCEDURE" for
how to replace pump.
2. Reduced flow in primary water circuit
Due to 1 or more of the following;
Faulty pump, insufficient air purge,
blocked strainer, leak in water circuit
2. Check circulation pump (See "10-6.
Checking Component Parts' Function" for
how to check).
Open purge valve to remove trapped air.
Check the strainer for blockages.
Check the primary water circuit for leaks.
Check that the flow amount is within the
recommended range.
3. Valve operation fault 3. Check valves on primary water circuit are
installed level.
4. 2-way valve (local supply) actuator
fault
4. Electrically test to determine fault.
5. 3-way valve actuator fault 5. 1) Electrically test to determine fault.
2) Operate 3-way valve manually using the
main remote controller. (Refer to
<Manual operation> in "9-4. Service
menu".)
3) Replace 3-way valve coil.
4) Replace 3-way valve. (Refer to Procedure
6 in “11. DISASSEMBLY PROCEDURE”.)
6. THW1 has become detached from its
holder.
6. Visually inspect location and reattach as
necessary.
7. THW1 or THW2 fault 7. Check resistance of thermistor against table
in "10-6. Checking Component Parts'
Function".
Compare FTC detected temperature to
hand held detector.
8. FTC board failure 8. Replace board.
OCH570C