Last edit: 07/08/2023
THE DOUBT
When analysing switchboards, we sometimes notice that the main disconnector-switch is installed directly on the door of the switchboard, instead of on the bottom plate, with an external operating handle rod. But is it permissible to install such a switch-disconnector on the door of a switchboard?
CONSIDERATIONS
Disconnecting an electrical circuit means interrupting its electrical (galvanic) continuity in a reliable manner, in order to allow an operator to work on the electrical parts of the machine. The general disconnecting device, i.e. the machine disconnecting device, separates the machine from the power supply (mains or electrical system).
The aim of the general disconnection device is to reduce the risk of direct contact. Direct contact occurs when a person comes into contact with active parts of the installation. All electrical equipment is required to have such external disconnection:
[IEC 60204-1] 5.3.4 "The operating means (for example, a handle) of the supply disconneting device shall be external to the enclosure of the eletrcial equipment."
The standard of reference for industrial control panels is IEC 60204-1; as can be read in paragraph 11.2.1 "Accessibility and maintenance", the standard prescribes that:
[IEC 60204-1] 11.2.1 “No devices, except devices for operating, indicating, measuring and cooling shall be mounted on doors or on access covers of enclosures that are expected to be removed”.
This is because every time the door is opened, the cables are subjected to mechanical stress, which can deteriorate the cable insulation over time. While it is permitted to carry a 230 Vac as part of the control system, it is not permitted to carry a 230 Vac or 400 Vac as part of the power circuit.
The solution is to install the switch-disconnector on fixed supports inside the panel, such as a plate, leaving only the external operation on the panel door, or making a cut-out in the door, as in the photo below. Alternatively, it is possible to install the switch disconnector with the external handle on the side, on the fixed wall adjacent to the main door of the switchboard.
CONCLUSIONS
It is therefore not legally permissible to install the power disconnector directly on the door of the switchboard. If you are unable to install it directly on the bottom plate of the switchboard, this article provides alternatives.