Safety Thermostat; Function; Checks - Savio GAIA 424 S Service Manual

20

Safety thermostat

20.1

Function

The safety thermostat (A in fig. 86) is a device that
senses the temperature of the main circuit water which
flows in the outlet pipe of the main heat exchanger.
If the temperature control system of the boiler fails and
the temperature of the main circuit reaches a danger-
ous temperature, the safety thermostat opens the elec-
tric circuit which supply the full sequence ignition de-
vice.
Consequently, the gas valve operators are no more
activated and the gas flow to the burner is stopped.
A
fig. 86
The safety thermostat does not re-- set automati-
cally. To reset, it is necessary to remove the plug B
and push the re-- set button with the help of a tool on
the instrument panel (fig. 87).
fig. 87
The safety thermostat has two parts:
the temperature probe C which is fitted on the
f
outlet pipe of the main heat exchanger (fig. 88)
B
and the electric switch D which is fitted in the con-
trol panel (fig. 89)
C
fig. 88
D
fig. 89
20.2

Checks

Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
Position of probe and integrity
n
Remove the front panel of the case and the sealed
chamber cover.
Verify the soundness of the fitting between the main cir-
cuit pipe and the temperature probe C (fig. 88).
Verify the integrity of the capillary which connects the
probe to the switch. If the capillary is broken the switch
opens automatically.
Overheat temperature value
n
Set the temperature control knobs to their max. position
and run the boiler in d.h.w. and c/h. Allow the boiler to
37