Contactors used in Safety Applications

Last edit: 26/08/2023

There are three types of contactors used in Safety-related control Systems:

  • Power Contactors: they have auxiliary Mirror contacts.
  • Auxiliary Contactors, also called Relays: they have auxiliary Positively Driven contacts.
  • Electromechanical elementary relays: among which there are relays with Forcibly Guided (mechanically linked) contacts. They are designed according to the IEC 61810-3 [35].


All three types can be used in a Safety-related control circuit, provided they are declared in compliace with their product standards:

  • Power Contactors: IEC 60947-4-1: Low-voltage switchgear and controlgear – Part 4-1: Contactors and motor-starters – Electromechanical contactors and motor-starters
  • Auxiliary Contactors: IEC 60947-5-1: Low-voltage switchgear and controlgear – Part 5-1: Control circuit devices and switching elements – Electromechanical control circuit devices.
  • Electromechanical elementary relays: IEC 61810-3: Electromechanical elementary relays – Part 3: Relays with forcibly guided (mechanically linked) contacts.

That declaration can be made by the component manufacturer and it does not require any third party certification, like it happens for components used in Low demand mode of operation.


The reliability parameter used for contctors is defined as B10 or B10D and its value is normally provided by the componet manufacturer. In case the value is not availbale, the machinery manufacturer can refer to Annex C of ISO 13849-1 or IEC 62061.


The values found in the Annex can be used provided the following conditions are met:

  • The components are manufactured according to basic and well-tried safety principles in accordance with ISO 13849-2:2012 and the relevant standard (see Table C.1) for the design of the component. That information can normally be found in the data sheet of the component manufacturer.
  • The manufacturer of the component specifies the appropriate application and operating conditions for the SCS or SRP/CS designer.
  • The design of the SCS or SRP/CS fulfils the basic and well-tried safety principles according to ISO 13849-2:2012, for the implementation and operation of the component.


Attention should be paid to the Electromechanical Relays: since the new edition of ISO 13849-1 (2023), those components can be used in Safety-related control circuits only if they are in compliance with IEC 61810-3.