4 Installation and Wiring
4-30
NJ-series CPU Unit Hardware User’s Manual (W500)
• To help prevent electrical shock, ground the ground terminal (GR: ) with a ground resistance of
less than 100 using a 14-gauge wire (minimum cross-sectional area of 2 mm
2
).
• The line ground terminal (LG: ) is a noise-filtered neutral terminal. If noise is a significant source of
errors or electrical shocks are a problem, connect the line ground terminal to the ground terminal and
ground both with a ground resistance of less than 100 .
• If the LG and GR terminals are connected, ground to a resistance of 100 or less to prevent electric
shock.
• The ground wire should not be more than 20 m long.
• The NJ-/CJ-series Controllers are designed to be mounted so that they are isolated (separated) from
the mounting surface to protect them from the effects of noise in the installation environment (e.g.,
the control panel).
• Do not share the Controller’s ground with other equipment or ground the Controller to the metal struc-
ture of a building. Doing so may worsen operation. Whenever possible, use an independent ground
(with the ground pole separated by a minimum of 10 m from any other ground pole).
• Ground to 100 or less, and if possible use a separate ground from those of other devices. (Refer to
figure (a) in the diagram below.)
• If using an independent ground is not possible, then use a common ground as shown in figure (b).
Connect to the ground pole of the other device.
Crimp Terminals
The terminals on the Power Supply Unit are M4, self-raising terminals with screws.
• Use crimp terminals for wiring.
• Do not connect bare stranded wires directly to terminals.
• Tighten the terminal block screws to the torque of 1.2 N·m.
• Use crimp terminals (M4) having the dimensions shown below.
Grounding
LG (Noise-filter neutral terminal)
Ground this terminal to less than 100
Ω
to improve noise resistance and prevent
electric shock.
GR (Ground terminal)
Ground this terminal to less than 100
Ω
to prevent electric shock.
Controller
Other
device
Ground of
100 Ω or less
ControllerController
(a) Independent grounds:
Best
(b) Common ground:
Acceptable
(c) Common ground:
Incorrect
Grounding Methods
Other
device
Other
device
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