Installing system components   
3.6 Connecting the connection box 
  Mobile Panels 2nd Generation 
64  Operating Instructions, 09/2018, A5E33876626-AC 
 
Connecting the functional grounding and power supply to the connection box 
The power supply for the HMI device is connected to a terminal strip in the connection box. 
The connection box has reverse polarity protection. 
 
If the supply voltage is outside the specified range, it may cause the HMI device to 
malfunction. This can result in personal injury or material damage. 
Use a 24 V DC power supply with the following properties for the connection box: 
•  Safe electrical isolation according to IEC 60364-4-41 or HD 384.04.41 (VDE 0100, 
Part 410). 
•  The power supply provides safety extra-low voltage according to SELV/PELV up to a 
maximum of 36 V DC and also does not exceed 
m
 = 36 V DC in case of fault. Refer to 
the information in the data sheet for overvoltage protection in the event of an internal 
error or take appropriate voltage-limiting measures, such as the use of a surge 
protection device. 
 
External protective circuit  
An external protective circuit is required for operation with 24 V DC; please refer to 
section 7 "Lightning protection and overvoltage protection" in the following function manual: 
"Designing interference-free SIMATIC S7-1500, ET 200MP, ET 200SP, ET 200AL 
controllers (https://support.industry.siemens.com/cs/ww/en/view/59193566
)". 
●  The power supply meets the requirements set out in  
"Technical specifications (Page 233)". 
●  The connection box standard or advanced is open. 
●  Read the information on power supply cables and equipotential bonding cable in the 
section "Specification of cables to be used (Page 242)". 
●  The wires of the power supply cable have been stripped by 8 mm. 
●  Matching ferrules when using flexible cables