Mitsubishi Electric PMCR-50VHA-200D KIT Installation Manual page 30

8. Troubleshooting
No. Fault symptom
8 Water heating takes longer.
9 Temperature of DHW tank
water dropped.
10 Hot or warm water from cold
tap.
11 Water leakage
12 Heating system does not
reach the set temperature.
13 The room temperature rises
during DHW operation.
14 Water discharges from
pressure relief valve.
(Primary circuit)
15 Water discharges from
pressure relief valve
(Sanitary circuit)
16 Noisy water circulation pump
17 Noise during hot water draw off
typically worse in the morning.
18 Mechanical noise heard
coming from the indoor unit.
19 Water circulation pump runs
for a short time unexpectedly .
en
20 Milky/Cloudy water
(Sanitary circuit)
21
FTC2BR that was running
in the heating mode before
power failure is running in
the DHW mode after power
recovery.
22
The cooling system does
not cool down to the set
temperature.
EN-30
Possible cause
1. Heat pump not working.
2. Booster heater cut-out tripped.
3. Booster heater breaker tripped.
4. Immersion heater cut-out has been triggered.
5. Immersion heater breaker tripped.
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 significant
drop in water temperature, check for the following.
1. Water leakage in the pipes that connect to the
DHW tank
2. Insulation material coming loose or off.
3. 3-way valve failure
Heat of hot water pipe is transferred to cold water
pipe.
1. Poorly sealed connections of water circuit
components
2. Water circuit components reaching the end of
life
1. The temperature sensor does not detect the
water temperature accurately.
2. Heat pump not working.
3. Booster heater cut-out tripped.
4. Booster heater breaker tripped.
5. Incorrectly sized heat emitter.
6. 3-way valve failure
3-way valve failure
1. If continual – pressure relief valve may be
damaged.
2. If intermittent – expansion vessel charge may
have reduced/bladder perished.
1. If continual – pressure reducing valve not
working.
2. If continual – pressure relief valve seat may
be damaged.
3. If intermittent – expansion vessel charge may
have reduced/bladder perished.
4. DHW tank may have subjected to backflow.
Air in water circulation pump.
1. Loose airing cupboard pipework.
2. Heaters switching on/off.
1. Heaters switching on/off.
2. 3-way valve changing position between DHW
and heating mode.
Water circulation pump jam prevention mechanism
(routine) to inhibit the build-up of scale.
Oxygenated water
FTC2BR is designed to run in an operation mode
with a higher priority (i.e. DHW mode in this case)
at power recovery.
When the water in the circulation circuit is unduly
hot, Cooling mode starts with a delay for the
protection of the outdoor unit.
Explanation - Solution
1. Check heat pump – consult outdoor unit service manual.
2. Check booster heater thermostat and press reset button if safe.
If the heater has been operated with no water inside it may have failed, so
please replace it with a new one.
3. Check the cause and reset if safe.
4. Check immersion heater thermostat and press reset button located on
immersion 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.
5. Check the cause and reset if safe.
1. Take the following measures.
• Retighten the nuts holding the pipes onto the DHW tank.
• Replace seal materials.
• Replace the pipes.
2. Fix insulation.
3. Check plumbing/wiring to 3-way valve.
Insulate/re-route pipework.
1. Tighten connections as required.
2. Replace them as necessary.
1. Check if the temperature sensor is affected by ambient temperature (except
water temperature).
2. Check heat pump – consult outdoor unit service manual.
3. Check booster heater thermostat and press reset button if safe.
If the heater has been operated with no water inside it may have failed, so
please replace it with a new one.
4. Check the cause of the trip and reset if safe.
5. Check the heat emitter surface area is adequate.
Increase size if necessary.
6. Check plumbing/wiring to 3-way valve.
Check the 3-way valve.
1. Turn the handle on the pressure relief valve to check for foreign objects in
it. If the problem is not still solved, replace the pressure relief valve with a
new one.
2. Check pressure in expansion vessel.
Recharge to 1 bar if necessary.
If bladder perished replace expansion vessel with a new one.
1. Check function of pressure reducing valve and replace if necessary.
2. Turn the handle on the pressure relief valve to check for foreign objects
inside. If the problem is not still solved, replace the pressure relief valve.
3. Check gas-side pressure in expansion vessel.
Recharge to correct precharge pressure if necessary.
If bladder perished replace expansion vessel with a new one with
appropriate pre-charge.
4. Check pressure in DHW tank. If pressure in DHW tank is similar to that in
incoming mains, cold water supply that merges with incoming mains water
supply could flow back to DHW tank. Investigate source of back-feed and
rectify error in pipework/fitting configuration. Adjust pressure in cold supply.
Use manual and automatic air vents to remove air from system.
Top up water if necessary to achieve 1 bar on primary circuit.
1. Install extra pipe fastening clips.
2. Normal operation no action necessary.
Normal operation no action necessary.
Normal operation no action necessary.
Water from any pressurised system will release oxygen bubbles when water is
running. The bubbles will settle out.
• Normal operation
• After the DHW max. operation time has elapsed or the DHW max.
temperature has been reached, the DHW mode switches to the other mode
(ex. Heating mode).
Normal operation