Function; Checks; Removal; Flue Temperature Probe Ntc And Safety Thermal Fuse - Biasi RIVA ADVANCE HE M110B.24SM/C Service Manual

20 Flue temperature probe NTC and
Safety thermal fuse
20.1

Function

The Flue temperature probe NTC A in Fig. 20.1 and
Fig. 20.2 senses the temperature of the combustion
products that flow through the condensing heat ex-
changer.
B
Fig. 20.1
If the temperature of the combustion products circuit
reaches the limit temperature, the Flue temperature
probe NTC reduces the gas flow rate to the burner. The
temperature of the combustion products should de-
crease to a safe value temperature.
In the case that the temperature of the combustion
products reaches a potentially dangerous value, it
stops the boiler operation (lock ---out).
This allows the use of plastic materials for the flue outlet
pipes and bends.
The use of kits different from the original isn't however
allowed, since the flue pipes are integral parts of the
boiler.
C
Fig. 20.2
A Safety thermal fuse B in Fig. 20.1 --- Fig. 20.2 is also
connected in series with the Flue temperature probe
A
A
B
NTC and acts as a safety device in extreme case of in-
correct operation of the Flue temperature control sys-
tem.
Reaching the breakdown temperature it opens the cir-
cuit and locks out the boiler.
In case of intervention of this safety device the heat ex-
changer (part shown in Fig. 20.3) may be damaged
and must be replaced.
Fig. 20.3
20.2

Removal

Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1 Remove all the case panels and the sealed
chamber lid.
2 Disconnect the connector C from the Flue tem-
perature probe NTC by pressing the plastic hook
placed on the side of the connector.
3 Unscrew and remove the flue temperature probe
A (Fig. 20.2) from the condensing heat ex-
changer.
4 Assemble the Flue temperature probe NTC carry-
ing out the removal operations in reverse se-
quence.
20.3

Checks

Overheat temperature value
n
1 Set the temperature control knobs to their max.
position and run the boiler in d.h.w. and c.h.
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 Flue temperature
probe NTC and no overheat intervention should
occur.
Temperature---resistance relationship
n
1 Remove the Flue temperature probe NTC (see
section 20.2).
2 Measure the Flue temperature probe NTC electri-
cal resistance at the ambient temperature and
check it according to the graph in Fig. 20.4
43