Emerson Rosemount 3490 Series Reference Manual page 28

Installation
January 2021
standards for surge immunity on power and signal lines, it is recommended that lightning
suppressors are also fitted if local conditions make this advisable.
3.4.4 Earthing connections
The IP-rated Rosemount 3490 Series Control Unit is double insulated and does not require
a mains earth.
Note
Do not connect terminal 30 to a mains earth. Terminal 30 is provided for use as an
intrinsically safe (or functional) earth connection, which must be used when a transmitter
is mounted in a hazardous area and is connected to terminals 1 and 2.
Terminal 3 is to be used for connection of a twisted-pair cable screen (shield) when the
control unit is powering the transmitter. This screen (shield) should be left unconnected at
the transmitter end unless there is a terminal provided for this purpose.
On the NEMA 4X-rated control unit, protective earth cables must be connected to at least
one of the bonding points on the inside of the enclosure. Bonding between cable/conduit
entries is not automatic and must be provided as part of the installation.
When connected to equipment located in a hazardous area, not meeting the
requirements of clause 6.3.13 (Isolation of circuits from earth or frame) in IEC
60079-11:2006 (EN 60079-11:2007), equipotential earthing must be ensured between
the equipment and the intrinsically safe earth. An example of equipotential earthing is a
cable with a cross-sectional area greater than 4 mm
Related information
Transmitter connections and cabling
3.4.5 Transmitter connections and cabling
Connection of a transmitter to the control unit does not confer intrinsic safety on the
transmitter. It is the responsibility of the user to ensure any transmitter installed in a
hazardous area is suitable for use and certified accordingly. The installation should be in
accordance with a recognized code of practice.
Check that the electrical parameters of the installed system of control unit, transmitter,
any loop-powered devices, and interconnecting cable to ensure compliance with the
product certificates and technical data. Particular attention must be given to the cable and
the transmitter to ensure that the total capacitance and inductance limits stated in the
technical data in
Cable joins are allowable in cabling the transmitter, provided that the joint is made within
an IP20/NEMA 3 (minimum) enclosure suitable for the environment, and that wiring
withstands a test voltage of 500 V r.m.s. to earth.
The maximum length of cable permissible between the transmitter and control unit is
determined by limits imposed by the intrinsic safety certificates of the instruments and
control drawings.
No other outputs from the control unit must be routed through a hazardous area unless
protected by an additional I.S. Barrier (not supplied).
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Product certifications are not exceeded.
Reference Manual
00809-0100-4841
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and a resistance of less than 1 ohm.
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