Annual Maintenance; Error Codes - Mitsubishi Electric EHST20-Serie Installationshandbuch

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Service and Maintenance

Annual Maintenance

It is essential that the cylinder unit is serviced at least once a year by a qualified
individual any spare parts required should be purchased from Mitsubishi Electric.
NEvEr bypass safety devices or operate the unit without them being fully opera-
tional.
<Draining the cylinder unit and its primary heating circuit (local)>
WArNING: DrAINED WATEr MAY BE vErY HOT
1. Before attempting to drain the cylinder isolate from the electrical supply to pre-
vent the immersion and booster heaters burning out.
2. Isolate cold water feed to tank.
3. Attach a hose to the tank drain cock (No. 17 on Figure 3.1 - 3.4). The hose
should be able to withstand heat as the emptied water could be very hot. The
hose should drain to a place lower than the tank bottom to encourage siphon-
ing.
Open a hot water tap to start draining without a vacuum.

Error Codes

Code Error
L1 Booster heater overheat detection
L2 Booster heater thermistor (THW3) failure
L3 Circulation water temperature overheat protection
L4 Tank water temperature overheat protection
L5 Indoor unit temperature thermistor (TH1, TH2, THW1, THW2, THW5B) failure
L6 Circulation water freeze protection
L7 3-way valve failure
L8 Heating operation error
L9 Low primary circuit flow rate detected by flow switch
J0 Communication failure between FTC3 and wireless receiver
J1 - J8 Communication failure between wireless receiver and wireless remote controller
E0 - E5 Communication failure between main controller and FTC3
E6 - EF Communication failure between FTC3 and outdoor unit
E9 Outdoor unit receives no signal from indoor unit.
U*, F* Outdoor unit failure
Note: To cancel error codes please switch system off (Press button E, on Main Controller, for 3 secs).
4. When the tank is drained close drain cock and hot tap.
5. Attach hose to booster heater drain cock and water circuit drain cock (No.13
and No. 16 on Figure 3.1 - 3.4). The hose should be able to withstand heat as
the emptied water could be very hot. The hose should drain to a place lower
than the booster heater drain cock to encourage siphoning. Open the pump
valves and the strainer valves.
6. Water remains in the strainer still after the cylinder unit was drained.
Drain the strainer by removing the strainer cover.
<Annual maintenance points>
Use the Annual Maintenance Log Book as a guide to carrying out the necessary
checks on the cylinder and outdoor unit.
Action
Flow rate may be reduced check for;
• Water leakage
• Strainer blockage
• Pump function (Error code may display during filling of primary circuit,
complete filling and reset error code.)
Check the resistance of the thermistor.
See Action for L1.
Check the immersion heater and it's contactor.
Check the resistance of the thermistor.
See Action for L1.
Check the motion of the 3-way valve.
Re-attach any thermistors that have become dislodged.
See Action for L1. If the flow switch itself does not work, replace it.
The pump valves may be hot, please take care.
Check connection cable for damage or lose connections.
Check wireless remote controller's battery is not flat.
Check the pairing between wireless receiver to wireless remote controller.
Test the wireless communication. (See the manual of wireless system)
Check connection cable for damage or loose connections.
Check that the outdoor unit has not been turned off.
Check connection cable for damage or loose connections.
Refer to outdoor unit service manual.
Check both units are switched on. Check connection cable for damage or
loose connections. Refer to outdoor unit service manual.
Refer to outdoor unit service manual.
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