Omron NX Series Hardware User Manual page 195

Each of these earthing methods is given below.
l Equipotential Bonding System
Equipotential bonding is an earthing method in which steel frames and building structures, metal
ducts and pipes, and metal structures in floors are connected together and make connections to
the earth trunk line to achieve a uniform potential everywhere across the entire building. We recom-
mend this earthing method.
The following figure shows an example of an equipotential bonding system.
Connect the main earthing terminal and building structures together with equipotential bonding con-
ductors and embed the mesh ground line in each floor.
Connect the ground line of each control panel to the equipotential bonding system.
Earth trunk line
Control panel
Equipotential bonding conductor
Building structure
l Star Earthing
If the earthing method used for the building is not equipotential bonding or the earthing system is
unknown, choose (a) from the earthing methods given below.
a. Installation method by connecting devices and noise sources to separate earth electrodes
This is an earthing method to separately ground an earth electrode of the device that is con-
nected with a communications cable or other devices and an earth electrode of a high-power
device that could be a noise source, such as a motor or inverter. Each earth electrode must be
ground to 100 Ω or less.
Connect the ground lines of the device that is connected with a communications cable and oth-
er devices as a bundle to a single earth electrode. Be sure that the earth electrode is separated
by a minimum of 10 m from any other earth electrode of a device that could be a noise source.
NX-series NX502 CPU Unit Hardware User's Manual (W629)
Power device
Information device
Control panel Control panel
Hub
Metal structure in floor
Earth electrode
Metal duct and pipe
Noise source
Main earthing terminal
5 Installation and Wiring
5-65
5