Mitsubishi Electric EHPT20Q-VM2EA Service Manual page 39

Error code Title and display conditions
L9 Low primary circuit (Heat source side) flow
rate detected by flow sensor
* "4" is displayed in "Request code: 569" in "Run-
ning information".
<Heating>
Error code displayed when flow sensor detects
low flow rate for 10 seconds.
Low primary circuit (Heat source side) flow
rate detected by flow sensor
* "5" is displayed in "Request code: 569" in "Run-
ning information".
<DHM/Heating/LP/LS>
Error code displayed when flow sensor detects
low flow rate for 10 seconds.
Exception
While hot water is not supplied.
LF Flow sensor failure
"*" is displayed in "Request code : 575" in
"Running information".
* ... 1 : Flow sensor 1
2 : Flow sensor A
3 : Flow sensor B
LP DHW supply temperature overheat protection
<HW/HT/FS/OS>
Error code displayed when THW4 detects a temp
≧ 70℃ for 5 concecutive seconds.
Exception
Error code will not be displayed if;
While there is no hot water supply,
For 30 seconds after hot water supply start,
DHW supply max. temp. is set to more than 61℃,
For 24 hours after DHW supply max. temp. is
changed from more than 61℃ to less than 60℃.
LU
Water circulation pump failure
"*" is displayed in "Request code:576" in "Running
information".
* ... 1: Water circulation pump 1
2: Water circulation pump A
<HW/HT/FS/OS>
Error code displayed when
PWM feedback signal is set to 83〜92% for 10
concecutive seconds.
Exception
Water circulation pump is OFF.
GCH15010
Possible Cause
1. 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. Valve operation fault
3. 2-way valve (local supply) actuator
fault
4. Connector wire has become detached
or loose wiring.
5. Flow sensor 1 fault
6. FTC board failure
1. 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. Valve operation fault
3. 2-way valve (local supply) actuator
fault
4. Connector wire has become detached
or loose wiring.
5. Flow sensor B fault
6. FTC board failure
1. Thermal store tank water tempareture
is high (THW5A≧70℃)
2. THW4 fault
3. FTC board failure
1. Power supply voltage increase
2. Connector/terminal wire has become
detached or loose wiring
3. Water circulation pump is locked
4. Water circulation pump reaching the
end of life
5. Water circulation pump fault
6. FTC board failure
39
Diagnosis and action
Check circulation pump (See 10-6. for how
1.
to check).
Open air vent 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 during heating
operation.
Refer to Procedure 5 in "11. DISASSEMBLY
PROCEDURE."
Check valves on primary water circuit are
2.
installed level.
Electrically test to determine fault
3.
4. Visually check the CN1A connector and
reattach if necessary.
5. Electrically test to determine fault.
See 10-6. for how to check.
6. Replace board.
Check circulation pump (See 10-6. for how
1.
to check).
Open air vent 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 during heating
operation.
Refer to Procedure 5 in "11. DISASSEMBLY
PROCEDURE."
Check valves on primary water circuit are
2.
installed level.
Electrically test to determine fault
3.
4. Visually check the CN2B connector and
reattach if necessary.
5. Electrically test to determine fault.
See 10-6. for how to check.
6. Replace board.
Check flow sensor cable for damage or loose
connections.
1. Refer to L3/L4.
2. Check resistance of thermistor against
table in section 10-6.
3. Replace board.
1. Check the supply voltage.
2. Visually check the terminals and connectors
and reattaches appropriate.
3. to 5.
Turn the power to the indoor unit OFF and
then ON.
Power to both the indoor unit and outdoor
unit should be switched OFF then ON.
If the LU code is still displayed the water
circulation pump should be replaced.
6. Replace board.