Grounding The Instrument - ABB LWT300 series User Manual

Grounding the instrument

NOTICE
Star or daisy chain configurations are not allowed under any circumstances.
The LWT must be grounded in accordance with national electrical codes, using a protective earth (PE)
terminal by means of a short connection to an equipotential bonding. The equipotential bonding
conductor must have a maximum cross-section of 4 mm² (12 AWG).
PE terminals are available inside and outside the instrument housing (see Figure 12). Both terminals are
electrically interconnected.
—
Figure 12 Position of the two PE terminals
If using the external PE terminal, you must connect the grounding wire to the monitored vessel.
When grounding the LWT with a shielded wire, connect the wire to the PE terminal located inside the
housing. That shielded wire should only be grounded at one end, not both.
NOTICE
The LWT instrument has a ½-inch NPT/M20 cable gland entry.
The most effective way to ground the LWT housing is a direct connection to a ground with a maximum
impedance of 5 mΩ.
Outside installations or installations exposed directly or indirectly to lightning discharges shall have
a secondary lightning protection module. Use of a protected terminal block in combination with a
lightning arrestor module is mandatory for the continuous protection of users and installations.
22
User Guide
Internal PE terminal
External PE terminal