Mitsubishi Electric EHSD-MEE - Page 48

48
Check 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>
Check code displayed when thermistor is at open
or short (see table).
Exceptions
Check code will not be displayed for TH2; During
defrost and for 10 minutes after defrost operation.
Check 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
THW5A
DHW tank water temperature thermistor (upper) −39ºC or below 88.5ºC or above
THW5B
DHW tank water temperature thermistor (lower) −39ºC or below 88.5ºC or above
THW6 Zone1 ow temperature thermistor −39ºC or below 88.5ºC or above
THW7 Zone1 return temperature thermistor −39ºC or below 88.5ºC or above
THW8 Zone2 ow temperature thermistor −39ºC or below 88.5ºC or above
THW9 Zone2 return temperature thermistor −39ºC or below 88.5ºC or above
LD THWB1 Boiler flow 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 controller
may be defective. (when Room temp.
is chosen for the Heating operation
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>
Check code displayed when THW1 detects
a temp. ≤ 1ºC for 10 consecutive seconds or
THW2 detects a temp. ≤ 3ºC for 10 consecutive
seconds.
Exception
Check code will not be displayed if;
FS function is disabled,
For 10 minutes after water circulation pump1 is
switched on.
1. Insu󰀩cient 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 ow in primary water circuit.
Due to 1 or more of the following;
Faulty pump, insu󰀩cient air purge,
blocked strainer, leak in water circuit
2. Check circulation pump (See "10-6. Check-
ing 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 ow 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 (local supply) 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.
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' Func-
tion".
Compare FTC detected temperature to
hand held detector.
8. FTC board failure 8. Replace board.
OCH815A