Mitsubishi Electric ecodan ECOSLIM150L-PP-MEUK Installation Manual page 72

Troubleshooting
28
XXXXXXXX XXXXXXX
No. Fault Symptom
17 After DHW operation
room temperature
rises slightly.
18
The room temperature
rises during DHW
operation.
19 Water discharges
from pressure relief
valve. (Primary circuit)
20
Water discharges
from pressure relief
valve (field supplied
item).
(Sanitary circuit)
21 Noisy water circulation
pump
22 Noise during hot
water draw off
typically worse in the
morning.
23 Mechanical noise
heard coming from
the hydrobox.
24
Water circulation
pump runs for a
short time unexpectedly
.
25 Milky/Cloudy water
(Sanitary circuit)
26 Heating mode has been on
standby for a long time
(does not start operation
smoothly.)
27 The hydrobox that was
running in the heating mode
before power failure is
running in the DHW mode
after power recovery.
Pre-Plumbed Slimline Cylinder Installation Manual
72
(continued)
Possible Cause
At the end of the DHW mode operation the
motorised valve diverts hot water away from
the DHW circuit into space heating circuit.
This is done to prevent the hydrobox
components from overheating. The amount
of hot water directed into the space heating
circuit varies according to the type of the
system and of the pipe run between the
plate heat exchanger and the hydrobox.
Motorised 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 – field supplied 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. motorised valve changing position
between DHW and heating mode.
Water circulation pump jam prevention
mechanism (routine) to inhibit the build-up of
scale.
Oxygenated water
The time of "Delay" set in "Economy settings
for pump" is too short. (Go to "Service
menu" "Auxiliary settings" "Economy
settings for pump").
The hydrobox is designed to run in an
operation mode with a higher priority (i.e.
DHW mode in this case) at power recovery.
Explanation - Solution
Normal operation no action necessary.
Check the motorised 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
precharge.
4. Check gas-side 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.
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).