Publication 1746-UM022B-EN-P - January 2005
2-8 Installing And Wiring Your Module
Wiring Your Module
Follow these guidelines to wire your input signal cables:
• Power, input, and output (I/O) wiring must be in accordance
with Class 1, Division 2 wiring methods [Article 501-4(b) of the
National Electrical Code, NFPA 70] and in accordance with the
authority having jurisdiction.
• Route thermocouple and millivolt signal wires as far as possible
from sources of electrical noise, such as motors, transformers,
contactors, and ac devices. As a general rule, allow at least 6 in.
(about 15.2 cm) of separation for every 120V ac of power.
• Routing the field wiring in a grounded conduit can reduce
electrical noise further.
• If the field wiring must cross ac or power cables, ensure that
they cross at right angles.
• For high immunity to electrical noise, use Belden™ 8761
(shielded, twisted pair) or equivalent wire for millivolt sensors;
or use shielded, twisted pair thermocouple extension lead wire
specified by the thermocouple manufacturer. Using the incorrect
type of convention thermocouple extension wire or not
following the correct polarity may cause invalid readings.
• Ground the shield drain wire at only one end of the cable. The
preferred location is at the shield connections on the terminal
block. (Refer to IEEE Std. 518, Section 6.4.2.7 or contact your
sensor manufacturer for additional details.)
• Keep all unshielded wires as short as possible.
• Excessive tightening can strip a screw. Tighten screws to 0.25
Nm (2.2 in-lb) or less, based on UL 1059, CSA C22.2 No. 158,
VDE 0110B 2.79 standards.
• Follow system grounding and wiring guidelines found in your
SLC 500 Modular Hardware Style User Manual, publication
1747-UM011 or 1747-SLC 500 Fixed Hardware Style User
Manual, publication 1747-6.21.
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