Mitsubishi Electric EHSC-VM6A Service Manual page 39

Error code Title and display conditions
L7 3-way valve failure (Valve direction
defaults to DHW circuit)
<Heating/FS>
Error code displayed when the THW1 temp.
detects ≤ 1ºC increase in 20 consecutive
minutes and THW5B increases ≥ 1ºC
increase in 20 consecutive minutes after both
compressor and booster heater are OFF then
one is switched on.
Exception
If simultaneous Heating and DHW operation
is selected error code will not be displayed.
L8 Heating operation error
<Heating/FS>
Error code is displayed when the following
3 conditions are met;
• When THW1 temp. detects ≤ 1 ºC increase
in 20 consecutive minutes and THW5B
increases ≤ 1 ºC in 20 consecutive minutes
after both compressor and booster eater
areOFF then one is switched on.
• When THW1 temp. detects ≤ 1 ºC increase
in 10 consecutive minutes after booster
heater is switched from OFF to ON.
• When THW1-THW2 < -5 ºC for 10
consecutive minutes.
L9 Low primary circuit fl ow rate detected by
fl ow switch
<DHW/Heating/LP/FS>
Error code displayed when fl ow switch
detects low fl ow rate for 10 seconds.
Possible Cause
1 3-way valve actuator fault
2 THW1 or THW5B fault
3
FTC3 board failure
The thermistor on the wireless remote con-
troller or the main remote controller may be
defective.
4 Incorrect setting of the Dip switch(es)
5 THW1 or THW5B has been detached from
its holder.
1 THW1 has become detached from its
holder.
2
Booster heater fault
3
THW1 or THW2 or THW5B fault
4
FTC3 board failure
1
Insuffi cient system head
2 Reduced fl ow in primary water circuit
Due to 1 or more of the following;
Faulty pump, insuffi cient air purge, blocked
strainer, leak in water circuit.
3 Valve operation fault
4 2-way valve (fi eld supply) actuator fault
5 Connector/terminal wire has become de-
tached or loose wiring.
6
Flow switch fault
7 FTC3 board failure
Incorrect setting of SW2-2.
8 Incorrect setting of the SW2-2
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Diagnosis and action
1 Electrically test to determine fault.
2 Check resistance of thermistor against table
in section 10-6.
Compare FTC3 detected temperature to
hand held detector.
3
Replace board.
4 Check the Dip switch setting(s)
5 Visually inspect location and reattach as
necessary.
1 Visually inspect location and reattach as
necessary.
2
Electrically test to determine fault.
See 10-6. for how to check.
3
Check resistance of thermistor against table
in section 10-6.
Compare FTC3 detected temperature to
hand held detector.
4
Replace board.
1
Refer to table in section 10-6. to determine
if system pump meets requirements.
If more head required either add an pump
of the same size or replace existing pump
with capacity model.
See 11. DISASSEMBLY PROCEDURE for
how to replace pump.
2 Check circulation pump (See 10-6. 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 Check valves on primary water circuit are
installed level.
4 Electrically test to determine fault.
5 Visually check the CN2 connector and IN2
terminal and reattach if necessary.
6
Electrically test to determine fault.
See 10-6. for how to check.
7 Replace board.
8 Check the SW2-2 setting.