230 Series Auger Packer
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GROUNDING RECOMMENDATIONS
A good grounding system is a major consideration in planning any electrical system. However, it is
essential for proper operation of the electronics that a low-impedance path to earth ground exist. All
filtering devices internal to the PLC require a good earth ground return. The structural ground present in
many industrial environments does not provide an adequate ground return. A supplementary grounding
electrode should be used to reduce the impedance of the earth ground return when direct-wire
connection to the power system is not feasible. As a minimum, a No. 12 AWG stranded copper wire
should be used to connect to the copper grounding electrode. The connection should exhibit very low DC
resistance (0.05 OHM) and low high-frequency impedance (such as copper lugs). Minimum wire sizes,
color coding, and general safety practices should comply with American National Standards and the
National Electrical Code.
Other earth ground sources are not as desirable as a copper ground stake. Green wire earth grounds
(safety grounds) brought into the control system from plants distribution networks tend to be very noisy.
In most plants, the green wire earth ground system is characterized by ground loops, multiple
terminations to different references, and long wire runs adjacent to motor power and other high-power
wiring. Conduit as an earth ground has even more problems. Though many installations use these
ground references successfully, the practice should be avoided.
AC POWER CONSIDERATIONS
Electrical devices should not be operated at the low end of their input power voltage rating for extended
periods of time. When input voltage is low, current input is forced higher to provide the devise with the
power of needs. Additional current means additional heating. When a system is to be installed where
long brownouts are known to occur, the user is advised to supply the PLC with power from a voltage
regulating transformer. Use of this type of transformer will provide normal voltage to the devices and
keep current within normal range.
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