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4. Requirements to be met by limiter
4.1 Reset with tool only
As called for by EN 50019, the limiter can be reset only with the help of a
tool. Because the thermostat boxes are screwed together, the reset button
can be accessed only by opening the cover with a tool.
4.2 Manual reset
The safety temperature limiter is equipped with a manual reset. Automatic
resetting is not possible. The safety temperature limiter must be reset by
hand with the manual reset button after the lockout condition has been
rectified.
4.3 Reset under normal operating conditions only
Resetting is possible only after the normal operating temperature has been
reached. At excessively high temperatures, the reset button is blocked
mechanically. Only when the temperature has dropped below the nominal
tripping temperature can the reset button be used.
4.4 Safeguarding
The setting ranges of the safety temperature limiter are selected in such a
way that a nominal tripping temperature of the limiter related to the tem-
perature classes cannot be exceeded.
In applications requiring a broader temperature range (because of the sen-
sor’s thermal resistance, for example), the setting plate can be sealed to
prevent unauthorized resetting of the nominal tripping temperature.
4.5 Independence from control system
The safety temperature cutout is installed independently of the automatic
control system. The control system may use either a capillary tube thermo-
stat or a Pt-100 resistance temperature detector in conjunction with an
electronic controller. The RTD is either part of an intrinsically safe circuit or
is itself built to comply with a standardized type of protection.
5. Installation
For installation/operation, always observe the Equipment Safety
Law, the rules of generally accepted engineering practice
(EN 60079-14), and the instructions stated in this Manual.
Carry out work on and recalibrations of the thermostats in the deener-
gized state only.
Temperature controller and safety temperature limiter T-M-20-S/+x+y/EX is
used for controlling or limiting the temperature of electric resistance
heaters in potentially explosive atmospheres. The temperature controllers
and safety limiter is designed for stationary installation only.
Summary of Contents for T-M-20-S EX Series
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