Terminal Block; Grounding - Spectrum Controls 1769 Series User Manual

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2.7.2 Terminal Block

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2.7.3 Grounding

The possibility exists that a grounded or exposed thermocouple can
WARNING
become shorted to a potential greater than that of the thermocouple itself.
Due to possible shock hazard, take care when wiring grounded or exposed
thermocouples. See Appendix B, Using Thermocouple Junctions.
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Chapter 2: Installation and Wiring
Routing field wiring in a grounded conduit can reduce electrical noise.
If field wiring must cross AC or power cables, ensure that they cross at
right angles
Provision shall be made to prevent the rated voltage being
exceeded by the transient disturbances of more than 140% of the
peak rated voltage.
The equipment shall be installed in an enclosure that provides a
degree of protection not less than IP 54 in accordance with EN
60079-0 and used in an environment of not more than pollution
degree 2. The enclosure shall be accessible only with the use of a
tool
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Power and input wiring must be in accordance with Class 1, Division 2
wiring methods, Article 501-4(b) of the National Electric Code, NFPA
70, and in accordance with the authority having jurisdiction.
Grounding to earth is accomplished through mounting of modules on rail.
Subject devices are for operation in Ambient Temperature Range: 0 °C to
+60 °C.
Do not use the module's NC terminals as connection points.
Do not tamper with or remove the CJC sensors on the terminal block.
Removal of one or both sensors will reduce accuracy.
For millivolt sensors, use Belden 8761 shielded, twisted-pair wire (or
equivalent) to ensure proper operation and high immunity to electrical
noise.
For a thermocouple, use the shielded, twisted-pair thermocouple
extension lead wires specified by the thermocouple manufacturer. Using
the incorrect type of thermocouple extension wire or not following the
correct polarity will cause invalid readings.
To ensure optimum accuracy, limit overall cable impedance by keeping a
cable as short as possible. Locate the module as close to input devices as
the application permits.
This product is intended to be mounted to a well-grounded mounting
surface such as a metal panel. Additional grounding connections from
the module's mounting tabs or DIN rail (if used) are not required unless
the mounting surface cannot be grounded.
Keep cable shield connections to ground as short as possible.
User's Manual Pub. 0300244-02 Rev. A
2-11