Annual Maintenance - Mitsubishi Electric Ecodan EHST20 serie Para El Instalador

7
Service and Maintenance
no. Fault symptom
22 Water discharges 1.
from expansion relief
valve - part of Inlet
2.
Control Group
(EHPT20X-VM2HB
only) (sanitary circuit).
3.
4.
5.
23 Noisy water circulation Air in water circulation pump.
pump
24 Noise during hot water 1.
draw off typically
worse in the morning.
2.
25 Mechanical noise 1.
heard coming from the
cylinder unit.
2.
26 Water circulation pump Water circulation pump jam prevention mechanism
runs for a short time (routine) to inhibit the build-up of scale.
unexpectedly.
27 Milky/Cloudy water Oxygenated water
(Sanitary circuit)
28 Heating mode has The time of "Delay" set in "Economy settings
been on standby for for pump" is too short. (Go to "Service menu"
a long time (does → "Auxiliary settings" → "Economy settings for
not start operation pump").
smoothly.)
29 The cylinder unit The cylinder unit is designed to run in an operation
that was running in mode with a higher priority (i.e. DHW mode in
the heating mode this case) at power recovery.
before power failure
is running in the DHW
mode after power
recovery.

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 by-
pass safety devices or operate the unit without them being fully operational.
<draining the cylinder unit and its primary heating circuit (local)>
WArninG: drAined WAter MAy Be Very HOt
1. Before attempting to drain the cylinder unit isolate from the electrical supply to prevent the immersion and booster heaters burning out.
2. Isolate cold water feed to DHW tank.
3. Attach a hose to the DHW tank drain cock (No. 17 on Figure 3.1 - 3.5). The hose should be able to withstand heat as the draining water could be very hot. The hose
should drain to a place lower than the DHW tank bottom to encourage siphoning.
Open a hot water tap to start draining without a vacuum.
4. When the DHW 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 - 3.5). The hose should be able to withstand heat as the drain-
ing 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 unit and outdoor unit.
55
Possible cause
If continual – field supplied pressure
reducing valve not working.
If continual – expansion relief valve may be
damaged.
If intermittent – expansion vessel charge
may have reduced/bladder perished.
DHW tank may have subjected to backflow.
Unit has overheated – thermal controls have
failed.
Loose airing cupboard pipework.
Heaters switching on/off.
Heaters switching on/off.
3-way valve changing position between
DHW and heating mode.
explanation - Solution
1. Check function of pressure reducing valve and replace if necessary.
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. 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. 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.
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.
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.
Increase the time of "Delay" in "Economy settings for pump" .
• 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).