User`s manual

6-6
Countermeasure 2: Underground wiring as a countermeasure of lightning.
When communication cables and input cables of the JW300 go out of a building,
place them underground. Provide junction for input/output signals using relays.
1. Underground cabling
In a lightning weather condition, the atmosphere is electrically charged and a wiring in the air
induces a voltage of over 24 VDC. Therefore, place the wiring under the ground.
As for the depth of cable installation, refer to local regulations.
2. Relay connection for the input/output signals using relays
The relay isolates the effects of lightning and minimizes the damage.
(4) Wire of signal cable for expansion
When turning ON/OFF of the magnet switch installed near the JW300 and the signal cable for
expansion, high noise and high voltage may occur to give bad effects on the operation of the
JW300. Therefore, for prevention of the noise occurrence, insert a noise killer, such as a varistor,
at the contact point of the magnet switch. Do not place the signal cable for expansion and the 5
VDC cable inside the duct, through which input/output signal lines and power lines are running.
Outside panel
60 cm or 120 cm below ground level
CR 2
CR 1
Load
Relay
PLC
Input
Output
COM
COM
Wiring duct
Input/output
signal lines
Magnet
switch
Varistor
Signal cable for
expansion
5 VDC cable