3 
 
[Installation Precautions] 
WARNING 
 Do not use the MELSEC-WS safety controller in flammable gas atmosphere or explosive gas 
atmosphere. Doing so may result in a fire or explosion due to such as an arc caused by switching 
the relays. 
 
 
CAUTION 
 Use the MELSEC-WS safety controller in an environment that meets the general specifications in 
this manual. Failure to do so may result in electric shock, fire, malfunction, or damage to or 
deterioration of the product. 
 Latch the module onto the DIN mounting rail. Incorrect mounting may cause malfunction, failure or 
drop of the module. 
 To ensure full electromagnetic compatibility (EMC), the DIN mounting rail has to be connected to 
functional earth (FE). 
Ensure that the earthling contact is positioned correctly. The earthling spring contact of the module 
must contact the DIN mounting rail securely to allow electrical conductivity. 
 Shut off the external power supply for the system in all phases before mounting or removing the 
module. 
Failure to do so may result in damage to the product. 
 Do not directly touch any conductive part of the module. 
Doing so can cause malfunction or failure of the module. 
 The MELSEC-WS safety controller is only suitable for mounting in a control cabinet with at least IP 
54 degree of protection. 
Failure to meet the installation method may cause the module to fail or malfunction due to the 
deposition of dust or the adhesion of water.