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12 SAFETY THERMOSTAT
12 .1 Function
The safety thermostat "A" in Figure 12.1 is a device that senses
the temperature of the primary circuit water which flows in the
outlet pipe of the condensing heat exchanger.
If the temperature control system of the boiler fails and the tem-
perature of the primary circuit reaches a dangerous temperature,
the safety thermostat opens the electric circuit that supplies the
on-off operators of the gas valve.
Consequently, the full sequence ignition device attempts to light
the burner and, at the end, locks the boiler and lights the lock-out
on the display.
Figure 12 .1
12 .2 Checks
Overheat temperature value
1 Run the boiler and set the temperature at maximum by press-
ing the appropriate key.
2 Allow the boiler to reach its maximum operating temperature
(monitor the temperature gauge on the instrument panel).
The boiler should maintain a temperature below that of the
safety thermostat and no overheat intervention should occur.
Warning: isolate the boiler from the mains electrici-
ty supply before removing any covering or compo-
nent .
Electrical function
1 Remove all the case panels and the lid of the sealed cham-
ber.
2 Disconnect the safety thermostat and check its electrical
function. Normally (no intervention) the contact must be
closed (electrical resistance zero Ω).
SAFETY THERMOSTAT
A
12 .3 Removal
Warning: isolate the boiler from the mains electrici-
ty supply before removing any covering or compo-
nent .
1 Remove all the case panels.
2 Disconnect the wiring "B" (detail in Figure 12.2).
3 Unscrew the screws "C" and remove the overheat thermo-
stat.
C
Figure 12 .2
4 Reassemble the overheat thermostat carrying out the opera-
tions in reverse order.
5 Apply an adequate quantity of heat conducting compound
between the pipe and the thermostat.
Warning: After cleaning or replacement as detailed
above, it is deemed necessary to undertake a com-
bustion analysis as detailed in section "8 .3 Adjust-
ment" on page 22 .
B
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