Requirements To Be Met By The Temperature Limiter; Temperature Limiter (Schematic); Reset By Hand Only; Reset By Hand Via Tool Or Keyed Lock - Raychem vNent NGC-20-C-E Installation, Operating And Maintenance Instructions

4.3 Requirements to be met by the temperature limiter

The 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.

4.3.1 Temperature limiter (schematic)

Figure 10: Limiter block diagram.

4.3.2 Reset by hand only

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.

4.3.3 Reset by hand via tool or keyed lock

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 Supervisor, NGC-UIT2/TOUCH1500 or the handheld configuration and monitoring device NGDC-CMA2 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.
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Reset
..........
SPI
Temperature -
controller
Alarm relay
R485
Set
Principle limiter analog circuit
..........
AND
RTD check
..........
..........
Temperatue control
L
..........
..........
– 12V
..........
load current ground fault
current sensor current sensor
ground
fault relay
N PE
limiter
relay
N-load L-load