Over-Temperature Protection - ero electronic ELK Manuel Utilisateur

Over-temperature protection

When designing any control system it is essential to
consider what will happen if any part of the system
should fail. In temperature control applications the
primary danger is that the heating will remain
constantly on. Apart from spoiling the product, this
could damage any process machinery being controlled,
or even cause a fire.
Reasons why the heating might remain constantly on
include:
•
the temperature sensor becoming detached from the
process
•
thermocouple wiring becoming short circuit;
•
the controller failing with its heating output
constantly on
•
an external valve or contactor sticking in the heating
condition
•
the controller setpoint set too high.
Where damage or injury is possible, we recommend
fitting a separate over-temperature protection unit, with
an independent temperature sensor, which will isolate
the heating circuit.
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Please note that the alarm relays within the
controller will not give protection under all
failure conditions.
Routing of wires
To minimise the pick-up of electrical noise, the
low voltage DC connections and the sensor
input wiring should be routed away from high-
current power cables. Where it is impractical
to do this, use shielded cables with the shield
grounded at both ends. In general keep cable
lengths to a minimum.
Part number HA028438. Issue 3.0. Oct-05