Appendix A: Safety Instructions – Ver. 2.00
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A.4
Thermal Safety Limits
The RHE21 with Ex-code A1, A2, C1 or C2 have the temperature class T4
The RHE21 with Ex-code AS or Cs must be installed in the safe area, therefor no temperature
class is specified for these units.
The ambient temperature must under no circumstances exceed the limits specified in chapter
A.10.
A.5
Grounding and Shielding
The RHE21 must be grounded.
The minimum cross section of the ground wire is 2.5mm². Wires with 2.5mm² can be connected
to the PE terminal 22 or to the M4 screw type terminal. Wires with a bigger cross section must
be connected to the M4 screw type terminal.
Shield between RHM and RHE:
IEC60079-0 recommends to ground shielded cables just on one end, normally outside the
hazardous area. On the other side the shield may be grounded via a 1nF capacitor.
In small installations (cable length typically less than 10m) the shield can be grounded on both
sides, provided that there is no potential difference between PE at the RHM and PE at the RHE.
This can be assumed if there is a good metallic contact or if a dedicated PE cable of at least 4mm²
connects the two grounding points.
Most RHM provide a PE terminal and terminal for grounding via 1nF. If there is no capacitive
ground, special measures might be required.
Power supply and I/O circuits:
I/O and supply cables should be shielded when fed outside the control cabinet. When unshielded
wires are used outside a building, dedicated surge suppressors must be used.
NOTE:
The intrinsically safe circuits for the RHM and for the analog input are connected to earth; along
the intrinsically safe circuits potential equalization must exist
A.6
Installation
All cable entries are for fixed installation only. Cables must be clamped to prevent pulling or
twisting.
RHE21-E* (ATEX/IECEx only):
The RHE21-E* have 2 cable glands M16x1.5 with a clamping range 4 – 11mm for I/O and power
supply.
Options with 2 threads M25 or ½” NPT or 3/4” NPT are available upon request. In that case the
user is responsible for using correspondingly certified cable glands.
The cable glands or adaptors must not be changed by the user.
Summary of Contents for RHE21
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