Mitsubishi Electric EHPT20Q-VM2EA Service Manual page 44

No. Fault symptom
10 Temperature of DHW When DHW operation is not running, the DHW
tank water dropped. 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. Insulation material coming loose or off.
2. 3-way valve failure
11 Hot or warm water Heat of hot water pipe is transferred to cold water
from cold tap. pipe.
12 Water leakage 1. Poorly sealed connections of water circuit
components
2. Water circuit components reaching the end of
life
13 Heating system does 1. Prohibit, schedule timer or holiday mode se-
not reach the set lected.
temperature.
2. The temperature sensor is located in a room
that has a different temperature relative to
that of the rest of the house.
3. Heat pump not working.
4. Booster heater cut-out tripped.
5. Booster heater breaker (ECB1) tripped.
6. The booster heater thermal cut-out tripped
and can not be reset using the manual reset
button.
7. Incorrectly sized heat emitter.
8. 3-way valve failure
9. Battery problem (*wireless control only)
14 In 2-zone value ON/ 1. When Zone1 and Zone2 are both in heating
OFF control, only mode, the hot water temperature in Zone2
Zone2 does not does not exceed that in Zone1.
reach the set tem-
2. Faulty wiring of 2-way valve
perature.
3. Faulty installation of 2-way valve
4. Incorrect setting of Running time
5. 2-way valve failure
GCH15010
Possible cause
-
Explanation - Solution
1. Fix insulation.
2. Check plumbing/wiring to 3-way valve.
(i) Manually override 3-way valve using the main remote controller. (Refer to
<Manual operation> in section 9-4.) If the valve does not still function, go to (ii)
below.
(ii) Replace 3-way valve motor. If the valve does not still function, go to (iii) be-
low.
(iii) Replace 3-way valve. (Refer to 11. DISASSEMBLY PROCEDURE.)
Insulate/re-route pipework.
1. Tighten connections as required.
2. Refer to PARTS CATALOG for expected part lifetimes and replace them as
necessary.
1. Check settings and change as appropriate.
2. Relocate the temperature sensor to a more suitable room.
3. Check heat pump – consult outdoor unit service manual.
4. Check booster heater thermostat and press reset button if safe.
Reset button is located on the side of booster heater, covered with black rub-
ber cap. (See 4. PART NAMES AND FUNCTIONS for position.)
5. Check the cause of the trip and reset if safe.
6. 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.
7. Check the heat emitter surface area is adequate
Increase size if necessary.
8. Check plumbing/wiring to 3-way valve.
(i) Manually override 3-way valve using the main remote controller. (Refer to
<Manual operation> in 9-4). If the 3-way valve does not function, 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.)
9. Check the battery power and replace if flat.
1. Normal action no action necessary.
2. Refer to installation manual, "5.3 2-zone valve ON/OFF control".
3. Check for correct installation. (Refer to the manual included with each motor-
ized mixing valve.)
4. Check for correct setting of Running time.
5. Inspect 2-way valve. (Refer to the manual included with each 2-way valve.)
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