Siemens Industry Online Support
Siemens AG
Entry type: Application example Entry ID: 109762616, Entry date: 09/08/2020

Door interlocking for distributed industrial control panels according to UL 508A and NFPA 79

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To protect persons from injuries caused by electricity, control panels that are operated in USA must be designed so that they ensure proper protection against direct contact. This means that no live parts can be touched under normal operating conditions.

Relevant USA standards specify that doors of enclosures shall be interlocked when applied in industrial control panels (UL508A) for industrial machinery (NFPA79). At the same time, enclosures shall be accessible for maintenance and service purposes by qualified personnel. This application solution enables electrical engineers to comply easily with all requirements, while at the same time saving effort and costs.

The application example comprises 3 options:

  • Electronic door interlocking with LOGO!
  • Electric door interlocking
  • Electronic door interlocking with SIMATIC





Circuit diagram, bill of materials and functional sequence    Final_V1.0_Enclosure_interlocking_en_0820_UL_Mark.pdf (1,6 MB) 

E- Plan file:   Registrierung notwendig  door_interlock_181207.zip (13,5 MB)
SHA-256 checksum:   Registrierung notwendig  Code_door_interlock_181207.txt (1 KB) *

LOGO program:  Registrierung notwendig  door_interlock_with_LOGO_UL508A_NFPA79.zip (17,6 KB)  
SHA-256 checksum:  Registrierung notwendig  Code_door_interlock_with_LOGO_UL508A_NFPA79.txt (1 KB) *

SIMATIC:   Registrierung notwendig  EnclosureInterlockingUL508Aen.zip (413,6 KB)     The file must be dearchived in TIA Portal V15.1 !
SHA-256 checksum:  Registrierung notwendig  Code_EnclosureInterlockingUL508Aen.txt (1 KB) *

* Information about SHA-256:  109483101

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