7
4. Failures
Symptoms
Reason
Operation
Front panel indicators are off.
Power supply failure.
Check the mains and the main fuses.
Check the WT-3 temperature cut-off.
Check the F2 fuse on ZIO-21 board.
Replace the control panel.
K indicator is blinking.
Asymetric mains supply
(only three phase boilers).
Check mains and the main fuses.
Check the WT-3 temperature cut out.
No transmission to ZIO board
Check the connection between power module and
the ZIO 21 board.
Replace power board.
Replace ZIO-21 board.
B indicator is blinking.
The flow value is „0” or is to low.
(below value of 5 l/min)
Heating is blocked.
Check the F1 pump fuse on ZIO21 board.
Air lock in the heating system, solve the problem.
Deaerate the pump and the heating system.
Circulating pump is blocked.
Circulating pump is blocked. Make a manual pump
run. Use the screw to rotate the rotor.
Replace pump.
Flow sensor failure.
Replace flow sensor.
Room thermostat heating start heating
and the C indicator on the
control panel is not off.
The room thermostat wiring connection
failure.
Check the room thermostat wiring connection.
Room thermostat failure.
Replace room thermostat.
ZIO 21 failure.
Replace ZIO 21 board.
The supply temperature is too low.
The heating box failure.
Change the heating box.
The A indicator is on
The boiler is heating only central heating
The three-way valve failure
Check the servo. Replace the servo of valve
ZIO 21 failure
Replace ZIO 21 board
Mains problem
Check the F1 fuse. Check the mains.
DHW temperature is too low.
The boiler is heating only the heating
system.
The A indicator is off
The DHWT thermostat or DHWT electronic
Sensor (DS 1820) failure
Replace DHWT thermostat or electronic sensor
(DS 1820)
ZIO 21 failure
Replace ZIO 21 board
Too low DHWT temperature settings
Set the higher temperature on the DHWT
thermostat or rise the DHWT temperature on the
control panel (for the electronic sensor DS 1820)
The supply temperature is too low
Heating box failure
Check or replace heating box.
The NA connector is opened by the
superior device.
The C indicator does not blink
RP connector opened
Check the room thermostat
Control panel failure PSK.P4
Replace front panel
Control panel indicators are blinking or
temperature indicator is blinking or the return or
supply temperature indicator is showing 99
O
C.
Return or supply temperature sensor.
Use the right arrow to view the return inlet and
flow outlet temperature. If the „E” symbol or 99 is
displayed replace the required sensor.
(Nominal resistance of the temperature sensor
10kΩ at 25
O
C).
Control panel failure
Replace the front panel PSK.P4
Table 2. EKCO.L1/EKCO36.L1 (PSK.P4)
