Last edit: 08/08/2025
Types of connection
For the connection of the electrical equipment for a furnace to the incoming supply, one of the following type of connection shall be selected:
- connnection via permanently installed cables;
- Connection via flexible cords which are permanently connected to the supply system and the terminals of the installation;
- Connection via flexible cords which are permanently connected to the equipment and which are connected to the supply system by a plug-and-socket combination
- For connection to the incoming supply, only polarized plug-and-socket combination as specified in EN IEC 60309-1:2022 shall be used. Control or safety circuits shall be supplied directly from the incoming supply via plug-and-socket combination.
Terminations
The connecting points shall be suitable for the cross-sectional area and type of conductors to be connected.
The terminals of the incoming supply shall be identifibly marked in accordance with EN IEC 60445:2021. The designations shall be consistent with the circuit documentation.
Connections to remote electrical equipment
The control cabinet has to be provided with terminals, plug-and-socket devices or equivalent connections; Their designations shall be consistent with the circuit diagram.
An adequate number and design of connections shall be provided for the protective conductors in the control cabinet or terminal box so that incoming or outgoing protective conductors can be individually connected. All of that need to be secured to prevent accidental loosening and shall be marked in accordance with EN IEC 60445:2021.
Plug-and-socket combinations need to be polarized if they aren’t in a electrical installation room, and be of the retaining type in order to avoid and prevent accidental disconnection.
Emergency Stop
In order to reduce the risk of hazards causing injury to persons, damage to equipment or work in progress, the emergency stop is necessary, which requirements depend on the type of hazard and plant.
It is necessary to stop the energy conversion in the furnace to achieve a safe status, by interrupting the fuel or other form of energy as fast as possible.
It shall be possible to initiate the emergency stop of the fueling system of the furnace, in the type of furnace where the termal output exceed 50kW, by a single human action, in the event of a hazardous situation arising.
It’s action consist in directly or indirectly switch those circuits and electrical equipment of a furnace which need to be switched off to prevent a hazardous situation occuring. The emergency stop device may be integrated into the safety-related system.
It can also be used as a supply disconnecting device, if it meets the conditions specified the point where we have talked about devices for disconnecting power supplies
Non-opening of contact elements due to permanent welding
The document affirms that the fault of a permanent weld preventing contact elements from opening can be excluded if contactors, relays, or auxiliary switches are protected by an appropriate overcurrent or current-limiting device. To determine the protective device’s rating, its nominal current must be multiplied by a safety factor of 0.6.
This affirmation isn’t in line with what the ISO 13849-1 says, more specifically we can’t avoid the fault it self but we can reduce the probabilty that the phenomena could manifest, like sayd in the following immage in the the point that says, contactors with small load.
