D8 Series User’s Guide
Chapter 2: Installation
26
CAUTION!
Do not wire bundles of low-voltage signal and control circuits next to
bundles of high voltage ac wiring. High voltage may be inductively coupled onto the low-
voltage circuits, which may damage the controller or induce noise and cause
poor control.
Physically separate high-voltage circuits from low-voltage circuits and from D8 hardware.
If possible, install high-voltage ac power circuits in a separate panel.
Wiring Recommendations
Follow these guidelines for selecting wires and cables:
• Use stranded wire. (Solid wire can be used for fixed service; it makes intermittent connections
when you move it for maintenance.)
• Use 20 AWG (0.5 mm
2
) thermocouple extension wire. Larger or smaller sizes may be difficult
to install, may break easily, or may cause intermittent connections.
• Use shielded wire. The electrical shield protects the signals and the D8 from electrical noise.
Connect one end of the input and output wiring shield to earth ground.
• Use copper wire for all connections other than thermocouple sensor inputs.
Table 2.1
–
Cable Recommendations
FUNCTION
MFR. P/N
NO. OF WIRES
AWG
MM
2
Analog Inputs
Belden 9154
Belden 8451
2
2
20
22
0.5
0.5
RTD Inputs
Belden 8772
Belden 9770
3
3
20
22
0.5
0.5
Thermocouple Inputs
Thermocouple
Ext. Wire
2
20
0.5
Control Outputs and
Digital I/O
Belden 9539
Belden 9542
9
20
24
24
0.2
0.2
Analog Outputs
Belden 9154
Belden 8451
2
2
20
22
0.5
0.5
Noise Suppression
The D8 outputs are typically used to drive solid state relays. These relays may in turn operate more
inductive types of loads such as electromechanical relays, alarm horns and motor starters. Such
devices may generate electromagnetic interference (EMI, or noise). If the controller is placed close
to sources of EMI, it may not function correctly. Below are some tips on how to recognize and avoid
problems with EMI.
For earth ground wire, use a large gauge and keep the length as short as possible. Additional
shielding may be achieved by connecting a chassis ground strap from the panel to D8 case.
