Mitsubishi Electric Ecodan EHST20 serie Para El Instalador página 55

7
Service and Maintenance
no. Fault symptom
14 In 2-zone tempera- 1. When Zone1 and Zone2 are both in heating
ture 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 motorized mixing valve
perature.
3. Faulty installation of motorized mixing valve
4. Incorrect setting of Running time
5. Motorized mixing valve failure
15 When a PUHZ-FRP The outdoor unit is set to have operation of the in-
outdoor unit is con- door unit of air conditioner take precedence over
nected, DHW or Heat- that of the cylinder unit, and in the main controller
ing operation cannot settings "Electric heater (Heating)" or "Electric
run. heater (DHW)" is turned off.
16 When a PUHZ-FRP When the outdoor unit is set to have cooling
outdoor unit is con- operation of the indoor unit of air conditioner take
nected and is in heat precedence over that of the cylinder unit, the out-
recovery operation, door unit controls the frequency of the compres-
the set temperature sor according to the load of air conditioner. The
is not reached. DHW and heating run according to that frequency.
17 After DHW operation At the end of the DHW mode operation the 3-way
room temperature valve diverts hot water away from the DHW circuit
rises slightly. into space heating circuit.
This is done to prevent the cylinder unit compo-
nents 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 cylinder unit.
18 The room tempera- 3-way valve failure
ture rises during DHW
operation.
19 Water discharges 1. If continual – pressure relief valve may be
from pressure relief damaged.
valve.
2. If intermittent – expansion vessel charge may
(Primary circuit)
have reduced/bladder perished.
20 Water discharges 1. If continual – field supplied pressure reducing
from pressure relief valve not working.
valve (accessory
2. If continual – pressure relief valve seat may
supplied item).
be damaged.
(Sanitary circuit)
3. If intermittent – expansion vessel charge may
have reduced/bladder perished.
4. DHW tank may have subjected to backflow.
21 Water discharges 1. If continual – field supplied pressure reducing
from temperature valve not working.
and pressure relief
2. If continual – temperature and pressure relief
valve (EHPT20X-
valve may be damaged.
VM2HB only) (Sani-
tary circuit)
3. If intermittent – expansion vessel charge may
have reduced/bladder perished.
4. DHW tank may have subjected to backflow.
5. Unit has overheated – thermal controls have
failed.
Possible cause
1.
2.
3.
4.
5.
Turn ON Electric heater (Heating) or Electric heater (DHW) using the main controller.
Normal operation no action necessary.
If Air-to-Water system is given priority in operation, comp Hz can be regulated de-
pending on the load of DHW or Heating. For more details, refer to the PUHZ-FRP
installation manual.
Normal operation no action necessary.
Check the 3-way valve.
1. Turn the handle on the pressure relief valve to check for foreign objects in it. If the
2. Check pressure in expansion vessel.
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
3. Check gas-side pressure in expansion vessel.
4. Check gas-side pressure in DHW tank. If pressure in DHW tank is similar to that in
1. Check function of pressure reducing valve and replace if necessary.
2. Turn the handle on the temperature and pressure relief valve to check for foreign
3. Check gas-side pressure in expansion vessel.
4. Check pressure in DHW tank. If pressure in DHW tank is similar to that in incom-
5. Switch off power to the heat pump and immersion heaters.
explanation - Solution
Normal action no action necessary.
Refer to "5.3 Wiring for 2-zone temperature control".
Check for correct installation. (Refer to the manual included with each motorized
mixing valve.)
Check for correct setting of Running time.
Inspect the mixing valve. (Refer to the manual included with each motorized mix-
ing valve.)
(i) Manually override 3-way valve using the main controller. (Refer to <Manual
operation> in 5.6). If the 3-way valve does not function, go to (ii) below.
(ii) Replace 3-way valve coil. 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 the service manual.)
problem is not still solved, replace the pressure relief valve with a new one.
Recharge to 1 bar if necessary.
If bladder perished replace expansion vessel with a new one.
the problem is not still solved, replace the pressure relief valve.
Recharge to correct precharge pressure if necessary.
If bladder perished replace expansion vessel with a new one with appropriate pre-
charge.
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.
objects inside. If the problem is not still solved, replace the temperature and pres-
sure relief valve with a new one.
Recharge to correct precharge pressure if necessary.
If bladder perished replace expansion vessel with a new one with appropriate pre-
charge.
ing 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 pipe-
work/fitting configuration. Adjust pressure in cold supply.
Leave water running.
Wait until discharge stops. Isolate water supply and replace if faulty.
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