Connecting To Power Supply And Bus System; Preparing The Connection - Siemens SITRANS LG260 Operating Instructions Manual

Safety instructions
Voltage supply
Connection cable
Cable glands
18
5 Connecting to power supply and bus
system
5.1

Preparing the connection

Always keep in mind the following safety instructions:
Warning:
Connect only in the complete absence of line voltage.
•
The electrical connection must only be carried out by trained
personnel authorised by the plant operator.
•
If overvoltage surges are expected, overvoltage arresters should
be installed.
The instrument requires an operating voltage of 8 ... 30 V DC. Operat-
ing voltage and digital bus signal are carried on separate two-wire
connection cables.
The instrument is connected with standard two-wire, twisted cable
suitable for RS 485. If electromagnetic interference is expected which
is above the test values of EN 61326 for industrial areas, screened
cable should be used.
Make sure that the cable used has the required temperature resist-
ance and fire safety for max. occurring ambient temperature
Use cable with round cross section for instruments with housing and
cable gland. Use a cable gland suitable for the cable diameter to
ensure the seal effect of the cable gland (IP protection rating).
Make sure that the entire installation is carried out according to the
Fieldbus specification. In particular, make sure that the bus is termi-
nated with suitable terminating resistors.
Metric threads
In the case of instrument housings with metric thread, the cable
glands are screwed in at the factory. They are sealed with plastic
plugs as transport protection.
You have to remove these plugs before electrical connection.
NPT thread
In the case of instrument housings with self-sealing NPT threads, it is
not possible to have the cable entries screwed in at the factory. The
free openings for the cable glands are therefore covered with red dust
protection caps as transport protection.
Prior to setup you have to replace these protective caps with ap-
proved cable glands or close the openings with suitable blind plugs.
On plastic housings, the NPT cable gland or the Conduit steel tube
must be screwed into the threaded insert without grease.
Max. torque for all housings, see chapter "Technical data".
SITRANS LG260 - Operating Instructions PBD-51041059