Mitsubishi EHPT20X-MHCW, Руководство по обслуживанию

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73
No. Fault symptom Possible cause Explanation - Solution
22 Water discharges from
expansion relief valve
- part of Inlet Control
Group
(EH*T20*-MHCW only)
(sanitary circuit)
1. If continual – field supplied pressure
reducing valve not working.
1. Check function of pressure reducing valve and replace if necessary.
2. If continual – expansion relief valve may be
damaged.
2. Turn the handle on the expansion relief valve to check for foreign objects
inside. If the problem is not still solved, replace the expansion relief valve
with a new one.
3. If intermittent – expansion vessel charge
may have reduced/bladder perished.
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 precharge.
4. DHW tank may have subjected to backflow. 4. Check pressure in DHW tank. If pressure in DHW tank is similar to that in
the 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.
5. Unit has overheated – thermal controls have
failed.
5. Switch off power to the heat pump and immersion heaters. Leave water
running. Wait until discharge stops. Isolate water supply and replace if
faulty.
23 Noisy water circulation
pump
Air in water circulation pump. Use manual and automatic air vents to remove air from system.
Top up water if necessary to achieve 1 bar on primary circuit.
24 Noise during hot water
draw off typically
worse in the morning.
1. Loose airing cupboard pipework. 1. Install extra pipe fastening clips.
2. Heaters switching on/off. 2. Normal operation no action necessary.
25 Mechanical noise
heard coming from the
cylinder unit.
1. Heaters switching on/off. Normal operation no action necessary.
2. 3-way valve changing position between
DHW and heating mode.
26 Water circulation pump
runs for a short time
unexpectedly.
Water circulation pump jam prevention mechanism
(routine) to inhibit the build-up of scale.
Normal operation no action necessary.
27 Milky/Cloudy water
(Sanitary circuit)
Oxygenated water Water from any pressurised system will release oxygen bubbles when water is
running. The bubbles will settle out.
28 Heating mode has
been on standby for
a long time (does
not start operation
smoothly.)
The time of “Delay” set in “Economy settings
for pump” is too short. (Go to “Service menu”
→ “Auxiliary settings” → “Economy settings for
pump”).
Increase the time of “Delay” in “Economy settings for pump” .
29 The cylinder unit
that was running in
the heating mode
before power failure
is running in the DHW
mode after power
recovery.
The cylinder unit is designed to run in an operation
mode with a higher priority (i.e. DHW mode in this
case) at power recovery.
• 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).
30
Cooling mode is NOT
available.
DIP SW2-4 is OFF. Turn DIP SW2-4 to ON. (Refer to “6-19. DIP switch functions”.)
31
The cooling system
does not cool down to
the set temperature.
1. When the water in the circulation circuit is un -
duly hot, Cooling mode starts with a delay for
the protection of the outdoor unit.
1. Normal operation.
2. When the outdoor ambient temperature is
lower than the preset temperature that acti -
vates the freeze stat function, Cooling mode
does not start running.
2. To run Cooling mode overriding the freeze stat function, adjust the preset
temperature that activates the freeze stat function.
(Refer to "<Freeze stat function>" on Page 49.)
32 The electric heaters are
activated shortly after
DHW or LP mode starts
running after Cooling
mode.
The setting time period of Heat-pump-only opera -
tion is short.
Adjust the setting time period of Heat-pump only operation. (Refer to “<Electric
heater (DHW)> on Page 47.
33
During DHW or LP
mode following the
cooling mode, error
L6 (circulation water
freeze protection error )
occurs and the system
stops all the operations.
The unit runs in Cooling mode when the outdoor
ambient temperature is lower than 10ºC (outside
of the guaranteed operating range).
(When defrosting operation is running at such a
low outdoor ambient temperature after Cooling
mode is switched to DHW or LP mode, the water
temperature in the cooling circuit drops too low,
which could result in L6 error to stop all the opera -
tions.
Do not run Cooling operation when the outdoor ambient temperature is lower
than 10ºC.
To automatically stop or recover only Cooling operation and keep other opera -
tions running, the freeze stat function can be used. Set the preset temperature
that activates the freeze stat function to adjust the outdoor ambient tempera -
ture as follows. (Refer to "<Freeze stat function>" on Page 49.)
Outdoor ambient temperature Cooling operation
3ºC higher than the preset temperature Stop
5ºC higher than the preset temperature Recover
OCH570C