Spectrum Controls 1769sc-IF8u - Manual (Page 35)

Chapter 3: Installation and Wiring 25
Field Wiring
Connections
System Wiring
Guidelines
Consider the following when wiring your system:
General
• 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.
• Channels are isolated from one another by ±10 Vdc maximum.
• Route field wiring away from any other wiring and as far as possible
from sources of electrical noise, such as motors, transformers,
contactors, and ac devices. As a general rule, allow at least 15.2 cm
(6 in.) of separation for every 120V of power.
• 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.
• If multiple power supplies are used with analog millivolt inputs, the
power supply commons must be connected.
• Provision shall be made to prevent the rated voltage being exceeded
by the transient disturbances of more than 40%.
• The system shall be mounted in an ATEX certified enclosure with a
minimum ingress protection rating of at least IP54 as defined in
IEC60529 or EN60529 and used in an environment of not more than
pollution degree 2.
• Earthing is accomplished through mounting of modules on rail.
• Subject devices are for operation in Ambient Temperature Range: 0 C
to +60 C
Terminal Block
• Do not remove the CJC sensor from the terminal block if
thermocouples are to be utilized. Removal of the sensor will reduce
accuracy.
• For millivolt and current sensors, use Belden 8761 shielded,
twisted-pair wire (or equivalent) to ensure proper operation and high
immunity to electrical noise.
• For RTD and resistance sensors, use Belden 9501 (2 wire), 9533 (3
wire) and 83503 ( for runs over 100 feet) or equivalent.
• For a thermocouple, use the shielded, twisted-pair thermocouple
extension lead wires specified by the thermocouple manufacturer.