Temperature Setting Secured And Locked To Prevent Manipulation; Changing Limiter Set Point; Procedure To Write New Temperature Set Point To Limiter - nVent Raychem NGC-20-C-E Installations-, Betriebs- Und Wartungsanleitung

4.3.4 Temperature setting secured and locked to prevent manipulation

The lock out temperature (set point) of the safety temperature limiter must be set in such a way that maximum T-class temperature
cannot be exceeded. The surface temperature of the heat-tracing cables is limited to the temperature applicable in this T class -5 K for
temperatures below or equal to 200°C or -10 K for temperatures greater than 200°C. Refer to section 4.4 below for the procedure to
change the safety limiter set point.
Independence from control system
The safety temperature limiter operates totally independent from the temperature control system and has an own temperature
input (RTD Limiter) In case of a defect to any part of the NGC-20 unit the device shall be de-energized before replacing the defective
equipment.

4.4 Changing limiter set point

Changing the set point of the limiter requires the combination of the internal limiter set button and an external user interface.

4.4.1 Procedure to write new temperature set point to limiter

In order to write a new set point to the temperature limiter a safety procedure needs to be followed. Changing the set point of the
temperature limiter requires the combination of the internal limiter set button as is shown in Figure 11 and a programming device. As
programming device one can use; Supervisor software, NGC-UIT2/TOUCH1500 terminal or the handheld configuration and monitoring
assistant CMA2.
The procedure to change the limiter set point is the same for all user interfaces. The configuration tool will write the new set point to the
input buffer of the NGC-20-CL-E controller. Only when the internal temperature set button is pressed will the new set point be forwarded
to the internal memory of the temperature limiter. The limiter set point button needs to be activated within a certain time after the buffer
has been loaded with the new set point. If the button has not been pressed before the programming window is elapsed, the buffer will
be emptied and the old value remains active. Once the new set point has been written the new or in case the write procedure was not
successful the old set point will be read back by the programming device as confirmation to the user. After changing the limiter set point
the user shall verify whether the set point has been updated correctly. The limiter set point can be shown on the NGC-20 hardware by
pressing and holding the black Limiter SET button. While the limiter set point is shown the red LED indicator marked with LIMITER will
blink. After the button is released the display will show the controllers measured temperature again and the LIMITER LED will go off.
Each time after the limiter set point has been altered a functional test as per paragraph 4.5.1 is to be performed.
RESET
Limiter reset button (rearm the limiter after it has tripped)
SET
Limiter temperature set button to be pressed after
LIMITER
the polling process has been initiated
Figure 11: Internal Limiter control buttons: Limiter (temperature) SET and Limiter RESET pushbuttons.
nVent RAYCHEM NGC-20
HEATER
ALARM
LIMITER
RS485
BLUETOOTH
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