thuba TMS Manuel page 15

Manual PTB 24 ATEX 1001 X
4. Requirements to be met by safety
temperature limitwer
4.1 Reset with tool only
As called for by EN IEC 60079-7, 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 limiters are equipped
with a reclosing lockout (Figure 1). Automatic
resetting is not possible. Each individual safety
temperature limiter must be reset by hand with
the manual reset button after the respective mal-
function has been rectified.
4.3 Reset under normal operating
conditions only
Resetting is possible only after the normal oper-
ating temperature has been reached. At exces-
sively high temperatures, the reset button is
blocked mechanically. Only when the tempera-
ture has dropped about 10 % below the tripping
temperature the reset button can be used.
4.4 Tamperproof setting
The limit value can be set with a screwdriver on
the setting range of the safety temperature lim-
iter. No mechanical pressure shall be exerted on
the setpoint spindle when doing this. The setting
of the limit value can be locked for example with
temperature-resistant screw locking varnish.
4.5 Independence from control system
The safety temperature limiter is installed inde-
pendently of the automatic control system. The
control system may use either a capillary tube
thermostat or a Pt-100 resistance temperature
detector in conjunction with an electronic con-
Edition April 2024
Copyright
thuba Ltd., CH-4002 Basel
Switzerland
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