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Siemens Desigo Desigo Room automation - Engineering, mounting and installation CM111043en_13
Smart Infrastrructure Wiring of field devices (without bus) 2020-04-30
7.3 Wiring for Relay outputs
· External fuse of max. T 10 A for protection of the PCB tracks.
· The maximum load of the relay contracts must be observed (see data sheets for
the corresponding devices). It may require a fusing <10 A.
· Relays have volt-free relay contacts.
The mains voltage / switching voltage (AC 230 V / AC/DC 24 V) must be
supplied as an external voltage to the terminals.
· The lines must be secured on the device with strain relief.
· The sizing and fusing of the lines are oriented to overall load and local
regulations.
Actuators up to 100 VA: Lengths of up to 300 m / 1000 ft are admissible.
Wiring must comply with local regulations.
Taking account of the permissible voltage drop, the cable between the switching
outputs and the equipment to be switched may be up to 300 m / 1000 ft long
(DXR2: 80 m / 260 ft).
The permissible lengths are calculated as follows:
Voltage drop of max. 7 % (1.68 V) on the AC 24 V operating voltage for the
actuator.
Cable cross section Cable length for AC 24 V
Power
2 VA 5 VA 10 VA 20 VA 50 VA
2.50 mm
2
/ AWG14 300 m
1000 ft
300 m
1000 ft
235 m
770 ft
120 m
390 ft
47 m
150 ft
1.50 mm
2
/ AWG16 300 m
1000 ft
300 m
1000 ft
150 m
500 ft
75 m
250 ft
30 m
100 ft
1.00 mm
2
/ AWG18 300 m
1000 ft
185 m
600 ft
95 m
300 ft
50 m
150 ft
20 m
60 ft
0.75 mm
2
/ AWG20 290 m
960 ft
120 m
380 ft
60 m
190 ft
30 m
95 ft
12 m
40 ft
The outgoing and return cables may each have the indicated length.
Use cable cross section suited for 10 A according to local regulation.
7.4 Connecting the differential pressure sensor
· Avoid bends and pressure when attaching the tube.
· Connect the "+" connection on the side with the higher pressure and the "–"
connection on the side with the lower pressure.
· A tube length of 2 m (6 ft) is recommended.
Cable length
AC 230 V
Cable length AC 24 V
Note
Cable cross sectio