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Limiter Current sensor input
For specific installations the limiter can be configured such that it will
allow for a temperature overshoot as long as there is no current flowing
to the heating system. This would be the case when the high temperature
is caused by an external heat source such as steam cleaning, exothermal
processes, etc..
Sensors are permanently monitored for short circuit and cable
breakage. In case an open / short input is detected, the limiter will trip
instantaneously.
Limiter Outputs
Limiter Control output
The relay output of the limiter is typically used to operate an external
electro mechanical relay (EMR). This relay will in case of excessive over
temperature isolate the load from the mains supply.
Limiter Alarm output
•
The limiter alarm output relay will change state (from NC to NO) if the
limiter is powered up the first time after a power outage.
•
The limiter set point is exceeded and thus the limiter has tripped.
•
An RTD failure is detected.
•
A limiter current transformer failure (if the limiter CT is being used)
is detected.
Limiter reset
Once the limiter has tripped it has to be reset manually. Resetting the
limiter will only be possible if the actual temperature measured by the
Pt100 is below the limit temperature minus the unit hysteresis.
The limiter can be reset using one of the following methods:
1. From the control panel on the HTC-915-CONT by pressing alarm and
SHIFT + RESET (assuming presence of the digital communication
between controller and limiter).
2. Via pushing and holding the RESET key on the limiter unit for t > 2
seconds.
3. Remotely via the external input of the HTC-915 and a remote contact.
4. Remotely via DCS system. (5 to 24 Vdc).
5. Remotely via the serial interface and the supervisor software.
For an extended installation instruction - See INSTALL-092
Warning
The nVent RAYCHEM HTC-915 control module must be protected by
external over current and disconnect devices.
Mounting Procedures
The HTC-915-LIM is designed for installation on a standard
35 mm x 7.5 mm (EN50022 compatible) DIN rail.
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