Mitsubishi Electric EHPT17X-VM6D Service Manual page 55

10-4. Self-diagnosis and action
Check if DIP SW is set correctly. (Refer to "6-9. DIP switch functions".)
Check code Title and display conditions
L3 Circulation water temperature overheat
protection
<DHW/Heating/Cooling/LP/FS/OS>
Check code displayed when THW1 detects a
temp. ≥ 80ºC for 10 consecutive seconds or
THW2 detects a temp. ≥ 80ºC for 10 consecutive
seconds.
DHW: Domestic hot water mode
Heating: Heating mode
Cooling: Cooling mode
LP: Legionella prevention mode
FS: Freeze stat
OS: Operation stop
TH1A/B: Room temp. thermistor
TH2: Liquid refrigerant temp. thermistor
THW1: Flow water temp. thermistor
THW2: Return water temp. thermistor
THW5B: DHW tank lower water temp. thermistor
THW6: Zone1 flow water temperature thermistor
THW7: Zone1 return water temperature thermistor
THW8: Zone2 flow water temperature thermistor
THW9: Zone2 return water temperature thermistor
THWB1: Boiler flow water temperature thermistor
Tank water temperature overheat protection
L4
<DHW/Heating/Cooling/LP/FS/OS>
Check code display when THW5B detects a
temp. ≥ 75ºC for 10 consecutive seconds.
OCH714E
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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. Valve operation fault
4. 2-way valve (local supply) actuator fault
5. 3-way valve actuator fault
6. Booster heater relay (BHC1, BHC2,
BHCP) operating fault
7. Power supply voltage increase
8. THW1 or THW5 has become detached
from its holder.
9. THW1 or THW2 fault
10. FTC board failure
1. 3-way valve actuator fault
2. Immersion heater relay (IHC) operating
fault
3. THW5B fault
4. FTC board failure
55
Possible Cause
1 Refer to table in "10-6. Checking Compo-
2. Check circulation pump (See "10-6. Check-
3. Check valves on primary water circuit are
4. Electrically test to determine fault
5. 1) Electrically test to determine fault.
6. Electrically test the relays (BHC1, BHC2,
7. Check the supply voltage.
8. Visually inspect location and reattach as
9. Check resistance of thermistor against table
10. Replace board.
1. 1) Electrically test to determine fault.
2. Check immersion heater relay (IHC).
3. Check resistance of thermistor against table
4. Replace board.
Diagnosis and action
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.
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.
installed level.
2) Operate 3-way valve manually using
the main remote controller. (Refer to
<Manual operation> in "9-5. Service
menu".)
3) Replace 3-way valve coil.
4) Replace 3-way valve. (Refer to Procedure
6 in "11. DISASSEMBLY PROCEDURE."
BHCP) to determine fault.
See "10-6. Checking Component Parts'
Function" for how to check.
necessary.
in "10-6. Checking Component Parts' Func-
tion".
Compare FTC detected temperature to
hand held detector.
2) Operate 3-way valve manually using
the main remote controller. (Refer to
<Manual operation> in "9-5. Service
menu".)
3) Replace 3-way valve coil.
4) Replace 3-way valve. (Refer to Procedure
6 in "11. DISASSEMBLY PROCEDURE."
in "10-6. Checking Component Parts' Func-
tion".
Compare FTC detected temperature to
hand held detector.