Heating system: general
Protection against overheating
Characteristic of "Thick Film" heaters
The leakage current generated by the heating element is proportional to the temperature. Therefore
is important to avoid overheating in order not to cause any damage.
Leakage current v. Temperature of the heating element:
Units tted with a differential switch
(2011/10 to 2013/05)
In these units it is the differential switch that acts
as protection against overheating. If leakage
current generated reaches the limit of the
differential switch, it cuts the power supply.
Untimely disconnection of the differential
switch is not necessarily related to overheating.
The maximum temperatures recorded in
service mode should be checked rst in the
Measurements chapter in real time.
The fact that our units are tted with a
differential switch does exempt you from installing
differential protection in the electrical cabinet
according to the standards in force in your country.
Units not tted with a differential switch
(from 2013/05)
The use of new-generation heating element has
allowed differential switches to be done away
with. In this case protection is ensured by a bi-
metal (klixon). Each heating zone is tted with
these, and they are connected in series in the
safety chain. In case of overheating the bimetal
shuts off the unit via the main contactor K1.
See also the chapter 'power supply, safety chain'.
Heater leakage current
Heater temperature
IX.07
v03 • July-2016 • Hen
Heating system module
Line Units Serial number (starting from) Sw Revision
VCCM
VCCWE
All ExxXH1009xxxxxxx
I [mA]
T [°C]
1
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