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Siemens
Desigo TRA Engineering, mounting and installation
CM111043en_09
Building Technologies
Wiring of power lines
2016-02-22
6.3.2 DXR2
Topology
: DXR2... room automation stations with AC 24 V supply can only be
wired in star topology or with stubs (no daisy chain wiring).
DXR2.E...
: AC 24 V grounded or not grounded
DXR2.M...
: AC 24 V must always be earthed at the transformer.
Consumption
: DXR2... room automation stations with AC 24 V supply are
limited to a consumption of 4 A / 100 VA.
The devices have an
internal 4 A fuse
which CANNOT be replaced.
An
external power supply
for field devices should be fused separately for
secure operation. It must
NOT be grounded
.
The external power supply must NOT be used to supply the triacs.
IEC installation
(International Electrotechnical Commission / International Installation Standards)
SELV / PELV
Class III
Transformer with unlimited
power
The over-current protective
device limits the energy in the
secondary circuit
.
DXR2.
M
...: PELV only!
must always be
grounded
at the transformer.
NEC Class 2 installation
(National Electric Code for North America)
A
Using an energy limited
transformer with
max. 100 VA
DXR2.
M
...: must always be
grounded
at the transformer.
B
Using a non energy limiting
transformer (
max. 400VA
)
The over-current protective
devices (T 4 A fuses) limit the
energy to 100VA or less.
Multiple fuses per transformer
may be used to provide
multiple isolated secondary
circuits.
AC 24V
400 VA
4A
Built-
in
4A
100
VA
4A
Built-
in
4A
100
VA
4A
Built-
in
4A
100
VA
4A
Built-
in
4A
100
VA
~
~
~
~
DXR2.
M
...: must always be
grounded
at the transformer.