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No. Fault symptom Possible cause Explanation - Solution
15 In 2-zone tempera-
ture control, only
Zone2 does not
reach the set tem-
perature.
1. When Zone1 and Zone2 are both in heating
mode, the hot water temperature in Zone2
does not exceed that in Zone1.
1. Normal operation, no action necessary.
2. Faulty wiring of motorized mixing valve 2. Refer to "5.3 Wiring for 2-zone temperature control" in installation manual.
3. Faulty installation of motorized mixing valve 3. Check for correct installation. (Refer to the manual included with each motor-
ized mixing valve.)
4. Incorrect setting of Running time 4. Check for correct setting of Running time.
5. Motorized mixing valve failure 5. Inspect the mixing valve. (Refer to the manual included with each motorized
mixing valve.)
16 When a PUHZ-
FRP outdoor unit is
connected, DHW or
Heating operation
cannot run.
The outdoor unit is set to have operation of the
indoor unit of air conditioner take precedence
over that of the hydrobox, and in the main remote
controller settings "Electric heater (Heating)" or
"Electric heater (DHW)" is turned o.
Turn ON Electric heater (Heating) or Electric heater (DHW) using the main re-
mote controller.
17 When a PUHZ-FRP
outdoor unit is con-
nected and is in heat
recovery operation,
the set temperature
is not reached.
When the outdoor unit is set to have cooling
operation of the indoor unit of air conditioner take
precedence over that of the hydrobox, the outdoor
unit controls the frequency of the compressor
according to the load of air conditioner. The DHW
and heating run according to that frequency.
Normal operation, no action necessary.
If Air-to-Water system is given priority in operation, comp Hz can be regulated
depending on the load of DHW or Heating. For more details, refer to the PUHZ-
FRP installation manual.
18 After DHW operation
room temperature
rises slightly.
At the end of the DHW mode operation the 3-way
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.
Normal operation, no action necessary.
19
The room tempera-
ture rises during DHW
operation.
3-way valve failure Check the 3-way valve.
20 Water discharges
from pressure relief
valve.
(Primary circuit)
1. If continual – pressure relief valve may be
damaged.
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. If intermittent – expansion vessel charge may
have reduced/bladder perished.
2. Check pressure in expansion vessel.
Recharge to 1 bar if necessary.
If bladder perished, replace expansion vessel with a new one.
21 Water discharges
from pressure relief
valve (eld supplied
item).
(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 – pressure relief valve seat may be
damaged.
2. Turn the handle on the pressure relief valve to check for foreign objects in-
side. If the problem is not still solved, replace the pressure relief valve.
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 appropri-
ate pre-charge.
4. DHW tank may have subjected to backow. 4. Check the 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 wa-
ter supply could ow back to DHW tank. Investigate source of back-feed and
rectify error in pipework/tting conguration. Adjust pressure in cold supply.
22 Noisy water circula-
tion 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.
23 Noise during hot wa-
ter draw o typically
worse in the morning.
1. Loose airing cupboard pipework 1. Install extra pipe fastening clips.
2. Heaters switching on/o 2. Normal operation, no action necessary.
24 Mechanical noise
heard coming from
the hydrobox.
1. Heaters switching on/o Normal operation, no action necessary.
2. 3-way valve changing position between DHW
and heating mode
25 Water circulation
pump runs for a short
time unexpectedly.
Water circulation pump jam prevention mecha-
nism (routine) to inhibit the build-up of scale
Normal operation, no action necessary.
26 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.
27
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” .
OCH815A
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