63
OCH714D
No.
Fault symptom
Possible cause
Explanation - Solution
9
Water heating takes
longer.
1.
Heat pump not working.
1. Check heat pump – consult outdoor unit service manual.
2. Booster heater cut-out tripped.
2. Check booster heater thermostat and press reset button if safe.
Reset button is located on the side of booster heater, covered with white rub
-
ber cap. See "4. PART NAMES AND FUNCTIONS" to find out its position.
3. Booster heater breaker (ECB1) tripped.
3. Check the cause and reset if safe.
4. The booster heater thermal cut-out has tripped
and cannot be reset using the manual reset
button.
4. Check resistance across the thermal cut-out, if open then connection is bro-
ken and the booster heater will have to be replaced.
Contact your Mitsubishi Electric dealer.
5. Immersion heater cut-out has been triggered.
5. Check immersion heater thermostat and press reset button located on immer-
sion heater boss, if safe. If the heater kept running with no water inside, this
may have resulted in failure, so replace it with a new one.
6. Immersion heater breaker (ECB2) tripped.
6. Check the cause and reset if safe.
7.
Flow rate of the sanitary circuit may be reduced.
7.
Check the following items
• Check for trapped air in water pump (sanitary circuit).
• Check if the speed of water pump (sanitary circuit) is set to 2.
• Check water pump (sanitary circuit) for malfunction. (Refer to "10-6.
Checking Component Parts' Function".)
• Replace plate heat exchanger (water - water) or scale trap, if there are a
blockage which blocks the sanitary circuit.
10 Temperature of DHW
tank water dropped.
When DHW operation is not running, the DHW
tank emits heat and the water temperature
decreases to a certain level. If water in the DHW
tank is reheated frequently because of a signifi
-
cant drop in water temperature, check for the
following.
1. Water leakage in the pipes that connect to the
DHW tank
1.
Take the following measures.
• Retighten the nuts holding the pipes onto the DHW tank.
• Replace seal materials.
• Replace the pipes.
2. Insulation material coming loose or off.
2.
Fix insulation.
3.
3-way valve failure
3.
Check plumbing/wiring to 3-way valve.
(i)
Manually override 3-way valve using the main remote controller. (Refer to
<Manual operation> in "9-5. Service menu".) If the valve does not still func
-
tion, go to (ii) below.
(ii)
Replace 3-way valve motor. If the valve does not still function, go to (iii)
below.
(iii) Replace 3-way valve. (Refer to "11. DISASSEMBLY PROCEDURE".)
4. Water pump (sanitary circuit) speed setting
failure
4. Water pump (sanitary circuit) MUST be set to speed 2
.
When it set to speed 1, hot water would be mixed with cold water due to
circulation.
11
Hot or warm water
from cold tap.
Heat of hot water pipe is transferred to cold water
pipe.
Insulate/re-route pipework.
12 Water leakage
1.
Poorly sealed connections of water circuit
components
1. Tighten connections as required.
2. Water circuit components reaching the end of
life
2.
Refer to PARTS CATALOG for expected part lifetimes and replace them as
necessary.
13 Heating system does
not reach the set
temperature.
1. Prohibit, schedule timer or holiday mode se-
lected or demand control input (IN4) or smart
grid ready (switch-off command).
1. Check settings and change as appropriate.
2. Check settings and change as appropriate.
2.
Check the battery power and replace if flat.
3. The temperature sensor is located in a room
that has a different temperature relative to
that of the rest of the house.
3. Relocate the temperature sensor to a more suitable room.
4.
Heat pump not working.
4. Check heat pump – consult outdoor unit service manual.
5. Booster heater cut-out tripped.
5. Check booster heater thermostat and press reset button if safe.
Reset button is located on the side of booster heater, covered with white rub
-
ber cap. (See "4. PART NAMES AND FUNCTIONS" for position.)
6. Booster heater breaker (ECB1) tripped.
6. Check the cause of the trip and reset if safe.
7. The booster heater thermal cut-out tripped
and cannot be reset using the manual reset
button.
7. Check resistance across the thermal cut-out, if open then the connection is bro-
ken and the booster heater will have to be replaced.
Contact your Mitsubishi Electric dealer.
8.
Incorrectly sized heat emitter
8. Check the heat emitter surface area is adequate
Increase size if necessary.
9.
3-way valve failure
9.
Check plumbing/wiring to 3-way valve.
(i)
Manually override 3-way valve using the main remote controller. (Refer to
<Manual operation> in "9-5. Service menu".) If the 3-way valve does not func
-
tion, go to (ii) below.
(ii) Replace 3-way valve
motor
. If the 3-way valve coil is replaced but the
3-way valve does not function go to (iii) below.
(iii)
Replace 3-way valve. (Refer to "11. DISASSEMBLY PROCEDURE"
.)
10.
Battery problem (wireless control only)
10.
Check the battery power and replace if flat.
11.
If a mixing tank is installed, the flow rate be
-
tween the mixing tank and the cylinder unit is
less than that between the mixing tank and
the local system.
11.
Increase the flow rate between the mixing tank and the cylinder unit decrease
that between the mixing tank and the local system.
