Mitsubishi Electric Melsec-Q172DCPU User Manual page 177

4 INSTALLATION AND WIRING
(g) Wiring of 200m (656.17ft.) or longer distance will give rise to leakage
currents due to the line capacity, resulting in a fault.
Refer to the troubleshooting chapter of the I/O Module User's Manual.
(h) As a countermeasure against the power surge due to lightning, separate the
AC wiring and DC wiring and connect a surge absorber for lightning (Refer
to Section 4.5.1(1)).
Failure to do so increases the risk of I/O device failure due to lightning.
(3) Grounding
For grounding, follow the steps (a) to (c) shown below.
(a) Use a dedicated grounding wire as far as possible.
(Ground resistance: 100 or less)
(b) When a dedicated grounding cannot be performed, use (2) Common
Grounding shown below.
Another
Multiple CPU
equipment
system
grounding
(1) Independent grounding.....Best
(c) For grounding a cable, use the cable of 2mm
Position the ground-contact point as nearly to the Multiple CPU system as
possible, and reduce the length of the grounding cable as much as possible.
Another
Multiple CPU
equipment
system
grounding
(2) Common grounding.....Good
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Another
Multiple CPU
equipment
system
(3) Joint grounding.....Not allowed
2
or more.