Flammable refrigerants: components, ATEX and safety measures

The growing use of flammable refrigerants is profoundly changing the design of refrigeration systems. R290, R32, and other fluids classified as A2L, A2, or A3 allow for lower GWP, but require a more careful assessment of components, potential ignition sources, refrigerant charge, and mitigation measures.

The latest technical guidelines clarify how to interpret the requirements applicable to valves, exchangers, compressors, electronic and electromechanical controls used in vapor compression systems with flammable refrigerants. A particularly important point concerns ATEX: using a flammable refrigerant does not automatically mean that every component of the system must be ATEX certified.

For manufacturers, designers and installers it is therefore essential to distinguish between the requirements of the individual component, the risk assessment of the entire system and the additional measures required in the specific installation conditions.

Flammable refrigerants: safety starts with system evaluation

The presence of a flammable refrigerant cannot be managed by simply replacing a component with a version declared compatible with the new fluid.

The starting point remains the risk assessment of the entire refrigeration system , considering architecture, quantity of refrigerant, location of the equipment, accessibility of the rooms and the possible consequences of a leak.

The safety standards in fact define requirements relating to:

• staff skills;
• refrigerant charge limits ;
• surface temperatures;
• prevention of ignition sources;
• installation features;
• management of any losses.

Charge limits, in particular, don't depend solely on the refrigerant used. They can vary depending on the system configuration, installation location, the number of people who can access the area, and the intended use of the equipment.

The final responsibility for safety therefore remains with those who design and implement the system, who must verify the correct application of the components and the compliance of the entire system with the applicable standards and regulations.

Compatible components: don't just look at the refrigerant

Compressors, valves, exchangers and electronic devices must be qualified for the actual operating conditions.

With a flammable refrigerant, at least three aspects become particularly important: pressure, surface temperature and the possibility that the component constitutes a source of ignition .

The classification required for pressure equipment may also change as a function of pressure, component size and fluid group, influencing the requirements applicable to design and material verification.

For components that could come into contact with leaked refrigerant, it is also necessary to evaluate the possible presence of hot surfaces, electrical arcs, sparks or other phenomena capable of igniting a flammable mixture.

The component manufacturer must therefore clearly define:

• compatible refrigerants;
• scope of application;
• allowable pressures;
• installation conditions;
• any limitations;
• necessary certifications or approvals.

The choice of the component cannot be separated from its position within the system and the loss scenario considered.

ATEX: Not all systems with R290 or A2L become ATEX zones

One of the most delicate aspects concerns the application of the ATEX requirements .

A refrigeration system containing a flammable refrigerant does not automatically generate a permanent ATEX zone. Refrigeration systems are typically designed as sealed systems, and in typical applications, the surrounding area is not necessarily classified as a potentially explosive atmosphere.

Indiscriminately requesting ATEX components can therefore lead to overspecification that is not always technically necessary.

The situation changes when, based on the risk assessment or the installation conditions, an ATEX zone is actually defined.

Particular attention is also required during service operations , because opening the circuit, recovery or other activities can temporarily create conditions different from normal operation.

In these cases, devices intended to remain powered in a hazardous area may require specific features. Examples include:

• emergency lighting;
• alarm systems;
• gas detectors ;
• emergency ventilation.

Portable tools suited to the conditions in which the intervention is carried out also become important for technicians.

The key point is therefore to avoid two extremes: underestimating the risk of flammability or automatically considering every R290 or A2L appliance as a fully ATEX system.

Gas detectors, valves and ventilation to mitigate a leak

When circuit design alone is not sufficient to keep the risk within the expected levels, specific mitigation measures can be introduced.

The goal is to identify a leak and intervene before the refrigerant concentration reaches the Lower Flammability Limit (LFL) , which is the minimum level at which a mixture of refrigerant and air can propagate a flame.

The main devices that can be used include:

• shut-off valves ;
• refrigerant detectors;
• emergency ventilators;
• air circulation systems.

A gas detector can, for example, detect an increase in refrigerant concentration and activate ventilation or command the shutdown of certain components and the closing of shut-off valves.

In a ventilated enclosure, the system can be designed to keep any leaking refrigerant confined and vented to the outside, preventing it from reaching dangerous concentrations in the occupied space.

Mitigation measures therefore become an integral part of the design and not simply accessories added later.

From component to entire refrigeration system

The transition to R290, A2L and other flammable refrigerants ultimately requires a change of perspective.

There is no single component that can automatically make the system safe. Safety arises from the interaction between refrigerant, charge, components, installation environment, control, ventilation, and maintenance methods.

The applications affected can be very diverse: R290 chillers, stand-alone commercial equipment, remote condensing units, split and multi-split systems, rooftops and equipment installed inside ventilated enclosures.

For professional refrigeration this means that the spread of low GWP refrigerants will have to be accompanied by an ever-increasing ability to design for risk , rather than simply replacing the fluid.