Installing Your
Programmable Controller
Chapter 4
4-18
If the mounting brackets of a chassis do not lay flat before the nuts are
tightened, use additional washers as shims so that the chassis will not be
warped by tightening the nuts. Warping a chassis could damage the
backplane and cause poor connections.
Make good electrical connection between each chassis, the backpanel, and
the enclosure through each mounting bolt or stud. Wherever contact is
made, remove paint or other non-conductive finish from around studs or
tapped holes so that good electrical contact is made at each bolt or stud.
Equipment Ground Conductor
In addition to the connection through each bolt or stud, use either 1-inch
copper braid or 8 AWG copper wire to connect between each chassis, the
enclosure, and a central ground but mounted on the backpanel. Figure 4.9
and Figure 4.10 show ground-bus connection details. Figure 4.11 shows
enclosure-wall ground connection details. Use a steel enclosure to guard
against EMI. If the enclosure door has a viewing window, it should be a
laminated screen or a conductive optical substrate to block EMI. Do not
rely on the hinge for electrical contact between the door and the enclosure;
install a bonding wire.
Figure 4.9
Ground Bus Connection Details
10308-I
ground bus
tapped hole
ground lug
bolt
star washer
