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12
Safety thermostat
12.1
Function
The safety thermostat A in Fig. 12.1 is a device that
senses the temperature of the primary circuit water
which flows in the outlet pipe of the condensing heat ex-
changer.
If the temperature control system of the boiler fails and
the temperature of the primary circuit reaches a dan-
gerous temperature, the safety thermostat opens the
electric circuit that supplies the on---off operators of the
gas valve.
Consequently, the full sequence ignition device at-
tempts to light the burner and, at the end, locks the
boiler and lights the lock ---out on the display.
Fig. 12.1
12.2
Checks
Overheat temperature value
n
1
Run the boiler and set the temperature at maxi-
mum by pressing the appropriate key.
2
Allow the boiler to reach its maximum operating
temperature. The boiler should maintain a tem-
perature below that of the safety thermostat and
no overheat intervention should occur.
30
A
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
Electrical function
n
1
Remove all the case panels.
2
Disconnect the safety thermostat and check its
electrical function. Normally (no intervention) the
contact must be closed (electrical resistance zero
Ω).
12.3
Removal
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1
Remove all the case panels.
Disconnect the wiring B (detail in Fig. 12.2).
2
3
Unscrew the screws C and remove the safety
thermostat.
Fig. 12.2
4
Reassemble the safety thermostat carrying out
the operations in reverse order.
5
Apply an adequate quantity of heat conducting
compound between the condensing heat ex-
changer and the thermostat.
Warning: After cleaning or replacement as
detailed above, it is deemed necessary to
undertake a combustion analysis as detailed
in chapter 8.3 section 11.
B
C
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