Mitsubishi Electric EHSD-MED Service Manual page 47

Check code Title and display conditions
L9 Low primary circuit (Zone2 side) flow rate
detected by flow switch
Note: "3" is displayed in "Request code: 569" in
"Running information".
LA Pressure sensor failure
LB High pressure protection
LC Boiler circulation water temperature overheat
protection
<DHW/Heating/LP/FS/OS>
Check code displayed when THWB1 detects a
temperature ≥80ºC for 10 consecutive seconds
LD Boiler temperature thermistor (THWB1) failure
LE Boiler operation error
<Heating>
Boiler is running and THW6 detects a
temperature <30ºC for consecutive 60 minutes.
LF Flow sensor failure
LH Boiler circulation water freeze protection
LJ DHW operation error (type of external plate HEX)
LL Setting errors of DIP switches on FTC control
board
P1 Indoor unit temperature thermistor (TH1A/TH1B)
failure
P2 Indoor unit temperature thermistor (TH2) failure
OCH712C
Possible Cause
1. Insufficient system head
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
3. Terminal wire has become detached or
loose wiring.
4. Flow switch fault
5. Incorrect setting of the SW3-3
6. FTC board failure
1. Connector/terminal wire has become
detached or loose wiring.
2. Pressure sensor fault
3. FTC board failure
1. Flow rate of the heating circuit may be
reduced.
2. Plate heat exchanger may be clogged.
3. Outdoor unit failure
1. The set temperature for Boiler is too
high.
2. Flow rate of the heating circuit from the
boiler may be reduced.
Refer to check codes (P1/P2/L5/LD).
1. THW6 has become detached from its
holder.
2. Incorrect wiring between FTC (OUT10)
and the boiler
3. Boiler fuel has run out or the system is
OFF.
4. Boiler failure
5. FTC board failure
Disconnection or loose connection of
flow sensor
Flow rate of the heating circuit from the
boiler may be reduced.
1. DHW tank water temp. thermistor
(THW5B) has become detached from
its holder.
2. Flow rate of the sanitary circuit may be
reduced.
Incorrect setting of DIP switches
1. Boiler operation
2. 2-zone temperature control
3. Multiple outdoor units control
Refer to check codes (P1/P2/L5/LD).
Refer to check codes (P1/P2/L5/LD).
47
Diagnosis and action
1. If more head required either add a pump of
the same size or replace existing pump.
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 flow amount is within the
recommended range.
3. Visually check the IN7 terminal and reat-
tach if necessary.
4. Electrically test to determine fault.
5. Check the SW3-3 setting.
6. Replace board.
1. Check pressure sensor cable for damage or
loose connections.
2. Electrically test to determine fault.
See "10-6. Checking Component Parts'
Function" for how to check.
3. Replace board.
1. Check water circuit.
2. Check the plate heat exchanger.
3. Refer to outdoor unit service manual.
1. Check if the set temperature for Boiler for
heating exceeds the restriction. (See the
manual for the thermistors "PAC-TH011HT-E")
2. Check for
• water leakage
• strainer blockage
• water circulation pump function
1. Visually inspect location and reattach as
necessary.
2. See the manual of the thermistors "PAC-
TH011HT-E".
3. Check the status of the boiler.
4. Check the status of the boiler.
5. Replace board.
Check flow sensor cable for damage or
loose connections.
Check for
• water leakage
• strainer blockage
• water circulation pump function
1. Check for disconnection of DHW tank water
temp. thermistor (THW5B).
2. Check for water circulation pump function.
1. For boiler operation, check that DIP SW1-1
is set to ON (With Boiler) and DIP SW2-6 is
set to ON (With Mixing Tank).
2. For 2-zone temperature control, check DIP
SW2-7 is set to ON (2-zone) and DIP SW2-
6 is set to ON (With Mixing Tank).
3. For multiple outdoor units control, check DIP
SW1-3 is set to ON on FTC (sub) that runs
DHW operation .