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Siemens Building Technologies
Installation guide
CA2Z3884en
Building Automation
08.2001
2
AC 230 V supply cables
Sizing and fuse protection of the supply cables depends on the total load and on local
regulations. The supply cables must be secured with cable restraints.
3
AC 24 V transformer sizing
The DESIGO RXA controllers have an AC 230 V supply voltage. They generate the
AC 24 V supply for the connected field devices.
The power amplifiers for the UA1T thermic valve actuators have an AC 24 V supply and
require a transformer. This transformer must satisfy the requirements specified in
EN 60742 for SELV low voltage.
The transformer sizing is based on the total power consumption of all connected
devices (for UA1T, refer to data sheet CA2N3591). The transformer secondary winding
must be fused.
4
Signal cables
The following applies to the signal cables of field devices such as temperature sensors,
room units, window switches, occupancy sensors, dew point sensors and electric
switches:
-
Use twisted, 2-core or multi-core round cable without a screen (standard
installation cable)
-
Single conductors and ribbon cable must not be used
-
Signal conductors may be routed together with mains cables (AC 230 V), but they
MUST be insulated from the mains in accordance with regulations and in
compliance with SELV requirements.
-
Signal conductors must
NOT be routed in the same cable as mains conductors.
Cable length and other specifications are as follows:
-
Max. length of single cable: 100 m
-
L&S Ni1000 sensors must not share ground conductors (source of measurement
errors)
-
Recommended cable cross-section: A
≥
1 mm
2
Max. length of single conductor with diameter
≥
0.6 mm: 100 m
The same ground conductors may be used for more than one signal input.
-
Max. length of single conductor where A
≥
1.0 mm
2
: 125 m (and see table)
-
Cable type: 2-core, twisted pair, unscreened
A
Diameter
Max. length of single cable
[mm
2
]
[mm]
[m]
1.00
1.15
125
0.75
0.98
115
0.50
0.80
75
Measured value input B1
(L&S Ni1000 sensor)
Signal inputs D…
Room unit
