Mitsubishi Electric EHST20C-VM6HA Service Manual page 47

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Error code
Title and display conditions
Low primary circuit flow rate detected by
L9
flow switch
<DHW/Heating/LP/FS>
Error code displayed when flow switch
detects low flow rate for 10 seconds.
Exception
For 3 mins after water circulation pump1 is
switched on.
E0/E4
Main controller communication failure
(Reception error)
Error code E0 is displayed if main controller
does not receive any signal from the indoor
unit for ref. address "0" for 3 mins.
Error code E4 is displayed if indoor unit
does not receive any data from the main
controller for 3 mins or indoor unit does not
receive any signal from the main controller
for  mins.
E3/E5
Main controller communication failure
(Transmission error)
Error code E3 is displayed if the main
controller an not find an empty transmission
path and thus fails to transmit for 6 secs
or the data received bythe main controller
is different to what was sent (by the main
controller) 30 consecutive times.
Error code E5 is displayed if the FTC3 can
not find an empty transmission path for 3
mins and thus cannot transmit or the data
sent by the FTC3 is different to what was
expected 30 consecutive times.
E6
Indoor/outdoor communication failure
(Reception error)
Error code E6 is displayed if after the power
is switched ON to the indoor unit, the FTC3
board does not receive any signal or the
signal receivedis not complete for 6 mins, or
after a period of operation the FTC3 board
does not receive any signal or the signal
received is not complete for 3 mins.
Possible Cause
Insufficient system head
1
Reduced flow in primary water circuit
2
Due to 1 or more of the following;
Faulty pump, insufficient air purge, blocked
strainer, leak in water circuit.
3
Valve operation fault
2-way valve (field supply) actuator fault
4
Connector/terminal wire has become
5
detached or loose wiring.
Flow switch fault
6
7
FTC3 board failure
Incorrect setting of SW2-2.
Incorrect setting of the SW2-2
8
Contact failure with transmission cable
1
Wiring procedure not observed.
2
(Cable length/cable diameter/number of
indoor units/number of main controllers)
3
Fault on the indoor unit FTC3 board section
controlling Ref. address "0"
Fault with the main controller circuit board
4
Electrical noise causes interference with
5
transmission/reception of data for main
controller.
1
 or more main controllers have been
connected to the FTC3.
Fault with main controller transmission/
2
receiving circuit board
Fault with the main controller circuit board
3
Electrical noise causes interference with
4
transmission/reception of data for main
controller.
Contact failure/short circuit/miswiring
1
Fault with outdoor unit transmission/
2
receiving circuit board
Fault with FTC3 transmission/receiving
3
circuit board
Electrical noise causes interference with
4
FTC3-Outdoor unit transmission cable.
47
Diagnosis and action
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.
Check circulation pump (See 10-6. for how
2
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.
Check valves on primary water circuit are
3
installed level.
4
Electrically test to determine fault.
5
Visually check the CNF connector and IN
terminal and reattach if necessary.
6
Electrically test to determine fault.
See 10-6. for how to check.
7
Replace board.
Check the SW2-2 setting.
8
Check connection cable for damage or loose
1
connections at the FTC3 and main controller
terminals.
2
Check main controller and FTC3 common
wiring max cable length 500 m.
Only use  core cable.
Only connect 1 main controller to 1 FTC3
indoor unit board.
3
5
to
If the problem is not solved by the above
measures then:
Turn the power to the indoor unit OFF and
then ON.
Power to both the indoor unit and outdoor
units should be switched OFF then ON. (This
may require switching 1 or 2 breakers de-
pending if the unit is powered independently
from the outdoor unit).
If the E4 code is still displayed the FTC3
and/or the main controller circuit board
should be replaced.
1
Only connect 1 main controller to 1 FTC3
indoor unit board.
2
4
to
Turn the power to the indoor unit OFF and
then ON.
Power to both the indoor unit and outdoor
units should be switched OFF then ON.
(This may require switching 1 or 2 breakers
depending if the unit is powered independ-
ently from the outdoor unit).
If the E3/E5 code is still displayed the FTC3
and/or the main controller circuit board
should be replaced.
Check the LED display on the outdoor unit
circuit board.
(Connect the A-control service tool, PAC-
SK52ST to test.) Refer to the outdoor unit serv-
ice manual for explanation of EA-EC codes.
1
Check the connections on the indoor and
outdoor units have not become loose and
that the connecting cable is not damaged.
2
4
to
Turn the power to the indoor unit OFF and
then ON.
Power to both the indoor unit and outdoor
units should be switched OFF then ON.
(This may require switching 1 or 2 breakers
depending if the unit is powered independ-
ently from the outdoor unit).
If the E6 code is still displayed the FTC3
and/or the outdoor unit circuit board should
be replaced.

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