Last edit: 08/08/2025
Introduction
This part of the EN 50156 specifies the requirements and recommendations for the application design and installation of electrical and control equipment for furnaces and ancillary equipmentand for the systems heated by the termal energy released in the furnace to ensure:
- safety of personnel, property and the environment;
- consistency of proper function.
The operating conditons of the furnace, the hazards of combustion and the safety of heated systems are considered.
A safety-related system consisting of safety devices for:
- monitoring of flames and other safety conditions on the firing.
- interrupting the flow of fuel to the furnace.
- ventilating the body of the furnace and the flue gas ducts.
- monitoring of safety condition of heated systems (e.g. water level limiter in steam boilers).
It may be necessary to ensure proper ignition and combustion of the fuel and to avoid the development, existence and/or ignition of an explosive fuel-air mixture, as well as to avoid damage to the heated system (as shown in figure 3.22).
The term “furnace,” unfortunately, is a source of misunderstanding. Here’s the standard definition:
[EN 50156: 2024] 3 Terms and definitions
3.25 Furnace: A structure in which heat is generated at a controlled temperature by burning fuel.
Note 1 to entry: The term “furnace” includes structures in which heat is generated by electricity and other forms of energy. This standard also applies to the electrical equipment of electrically heated or waste heat steam boilers.
An inexperienced person might assume that all types of furnaces fall under this standard. In reality, only boilers must follow these requirements. For all other types of furnaces, the standards to follow are ISO 13577-2 and ISO 13577-4. For example, heat treatment furnaces or metal treatment furnaces must follow the requirements of these latter standards.
The rating of necessary safety integrity levels is based on EN 61508-1:2010.
Scope
This document applies to the application desgin and installation of electrical equipment, safety-related systems and control circuits for Boilers which are operated with solid, liquid or gaseous fuels and their accessory equipment.
It sets the guideline for the requirements that need to be met in order to have correct operating conditions, reduce eventual risks and hazards related to combustion and to protect the heated systems from eventual damage caused by the prevoius things mentioned.
Such boilers and the electrical equipment can be a part of the following plant:
- water heating systems
- steam boiler installations (steam and hot-water boilers) and heat recovery steam boilers;
- warm air heaters;
- hot-gas heaters;
- heat exchanger systems;
- combustion chambers of stationary turbines;
The standard indicates that EN 50156-1 can also be used ad a reference for electrical equipment requirements for thermo-processing equipment, but we do not recommend it.
It also specifies special requirements for the management of functional safety