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4.3 Requirements to be met by the temperature limiter
4.3.1 Temperature limiter (schematic)
Figure 10: Limiter block diagram.
4.3.2 Reset by hand only
4.3.3 Reset by hand via tool or keyed lock
16
The DigiTrace NGC-20-CL-E safety temperature limiter meets the requirements of
IEC 60079-30-1 For applications installed in a hazardous area Zone 1 (Zone 21) this
means that the protective device shall de-energize the system to prevent exceeding
the maximum permissible surface temperature. In case of an error by, or damage to
the sensor, the heating system shall be de-energized before replacing the defective
equipment. The protective device operates independently from the temperature
controller.
Reset
Set
..........
SPI
Temperature -
controller
Alarm relay
R485
The safety temperature limiter is designed such that after the temperature limiter has
tripped the device needs to be reset by hand. Resetting is possible only after the normal,
safe operating conditions have returned.
In order to RESET the limiter after it has tripped, the user needs to press the internal
Limiter Reset pushbutton as is shown in Figure 11. The figure shows where the limiter
RESET button is located inside the enclosure (lid removed). Alternatively the safety
temperature limiter can be reset via DigiTrace Supervisor, DigiTrace NGC-UIT or the
handheld configuration and monitoring device DigiTrace NGC-CMA and keying a specific
number on the keyboard. Refer to the operating manual of the specific units for more
detailed instructions on how to use these devices.
ZIEGLER ENGINEERING
Principle limiter analog circuit
AND
..........
..........
..........
RTD check
..........
..........
load current
current sensor
Temperatue control
L
N
ü
www.ze-gmbh.de
š
info@ze-gmbh.de
– 12V
..........
ground fault
current sensor
ground
limiter
fault relay
relay
PE
L-load N-load
NGC-20 INSTALLATION MANUAL
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