Connecting To Power Supply; Preparing The Connection - Siemens SITRANS LG270 Operating Instructions Manual

Safety instructions
Voltage supply via mains
voltage
Voltage supply via low
voltage
Connection cable
Cable glands
24
5

Connecting to power supply

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.
Note:
Install a separating facility for the instrument which is easy to access.
The separating facility must be marked for the instrument (IEC/
EN 61010).
In this case, the instrument is designed in protection class I. To main-
tain this protection class, it is absolutely necessary that the ground
conductor be connected to the internal ground terminal. Take note of
the national installation regulations.
Supply voltage and current signal are carried on separate connection
cables if reliable separation is required. The supply voltage range can
differ depending on the instrument version.
The data for power supply are specified in chapter "Technical data".
In this case, the instrument is designed in protection class II. Gener-
ally connect the instrument to vessel ground (potential equalization)
or with plastic vessels to the next ground potential. For this purpose, a
ground terminal is located laterally on the instrument housing.
An approved, three-wire installation cable with PE conductor is
required for voltage supply with mains voltage.
The 4 ... 20 mA current output is connected with standard two-wire
cable without screen. If electromagnetic interference is expected
which is above the test values of EN 61326-1 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 a cable gland suitable for the cable diameter to ensure the seal
effect of the cable gland (IP protection).
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.
SITRANS LG270 - Operating Instructions PBD-51041064