Installation Instructions

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Siemens Desigo Room automation - Engineering, mounting and installation CM111043en_14
Smart Infrastructure Wiring of field devices (without bus) 2020-10-30
7.2 Wiring for Triac outputs AC 24 V
The following applies for wiring to actuating devices such as valves, damper
actuators or protection connected to the Triac outputs:
· Use stranded, 2 or multiple core round cables, screened (standard off-the-shelf
installation cable).
· Single wires may not be used.
· Wiring may be laid together with power lines (AC 230 V).
They must be isolated from the power lines per regulations. Isolation must meet
PELV requirements.
· Wiring cannot be led in the same cable as the power lines.
Cable length and cross section
· Triacs are protected against overload.
· Cable cross section >= AWG20 / 0.75 mm
2
.
· Cable length <= 80 m / 260 ft (EM interference).
· Use cable cross section suited for 10 A according to local regulations
(M 10 A fuse in the power supply module / room automation station).
· Cable length <= 300 m / 1000 ft (EM interference).
Calculation is based on a voltage drop of 0.48 V = 2% of 24 V (the triac and the
PTC protection resistor have a voltage drop of 6%).
Cable cross section Cable length
Power
1 VA 2 VA 5 VA 10 VA 20 VA
2.50 mm
2
/ AWG14 300 m
1000 ft
300 m
1000 ft
140 m
440 ft
70 m
220 ft
35 m
110 ft
1.50 mm
2
/ AWG16 300 m
1000 ft
210 m
700 ft
85 m
280 ft
42 m
140 ft
21 m
70 ft
1.00 mm
2
/ AWG18 270 m
880 ft
135 m
440 ft
50 m
180 ft
25 m
90 ft
13 m
45 ft
0.75 mm
2
/ AWG20 170 m
550 ft
85 m
275 ft
33 m
110 ft
16 m
55 ft
8 m
27 ft
· The outgoing and return cables may each have the indicated length.
· Power = permanent load. The higher starting current of thermal or motorized
actuators is admissible.
Cable material
Cable laying
DXR2...
room automation
stations
PXC3 with TX-I/O triac
modules:
Caution!
Cable length
Notes