8
Installation RSP 20/25/30/35
Release
 
15
 
12/2017
 Supply voltage
The supply voltage is connected to the device casing through protective 
elements exclusively.
 For supply voltage connections with protective conductor connection: 
First connect the protective conductor before connecting the wires for 
the supply voltage. 
 For device variants featuring supply voltage with characteristic value 
CC and TT: 
For the redundant power supply, only use voltage sources whose 
negative terminal is grounded. The use of different voltage sources 
can lead to equipment damage. 
Only device variants 
featuring supply 
voltage with 
characteristic value 
TT: 
The wire diameter of the power supply cable is at least 0.75 mm² (North 
America: AWG18) on the supply voltage input.
The following requirements are alternatively complied with:
Alternative 1 The power supply complies with the requirements 
for a limited power source (LPS) as per EN 60950-1.
Alternative 2 All of the following requirements are complied with:
 The power supply complies with the 
requirements for a safety extra-low voltage 
(SELV) as per IEC/EN 60950-1.
 A fuse suitable for DC voltage is located in the 
plus conductor of the power supply. 
The minus conductor is on ground potential. 
Otherwise, a fuse is also located in the minus 
conductor.
Regarding the properties of this fuse: 
See “General technical data” on page 49.
Alternative 3 Relevant for North America:
The power supply complies with the requirements 
according to NEC Class 2.
Only for device 
variants featuring 
supply voltage with 
characteristic 
value K9 or KK:
All of the following requirements are complied with:
 Supply with DC voltage:
A fuse suitable for DC voltage is located in the plus conductor of the 
power supply. 
The minus conductor is on ground potential. Otherwise, a fuse is also 
located in the minus conductor.
Regarding the properties of this fuse: 
See “General technical data” on page 49.
The wire diameter of the power supply cable is at least 1 mm² (North 
America: AWG16) on the supply voltage input.
 Supply with AC voltage:
A fuse is located in the outer conductor of the power supply.
The neutral conductor is on ground potential at both voltage inputs. 
Otherwise, a fuse is also located in the neutral conductor.
Regarding the properties of this fuse: 
See “General technical data” on page 49.
The wire diameter of the power supply cable is at least 0.75 mm² 
(North America: AWG18) on the supply voltage input.
Device variant Requirements
Table 3: Requirements for connecting the supply voltage