Switching from HFC to CO2 (R744) or propane (R290) step by step

When is a switch relevant?

Since 1 January 2025, virgin F-gases with a GWP of 2,500 or more may no longer be used to service refrigeration equipment. Reclaimed or recycled gas may be used until the end of 2029, and from 2032 the limit is tightened to GWP 750 ^[1]. Centralised commercial systems of 40 kW or more with a GWP of 150 or more may no longer be placed on the market ^[1]. At the same time the HFC quotas are falling, which raises prices and reduces availability ^[1]. A switch is usually worth considering when:

• the plant runs on R404A, R507A or another refrigerant that is covered by a service ban, or will be from 2032,
• the plant leaks often or needs a large repair, such as a new compressor rack or new pipework,
• the store or building is being rebuilt or extended anyway,
• the operator wants lower costs for refrigerant and leak checks.

For a small plant, a retrofit to a lower-GWP HFC/HFO blend can be a first step. The retrofit calculator shows which alternatives fit.

Why you normally cannot fill R744 or R290 in an HFC system

An HFC system has a maximum allowable pressure (PS) chosen for HFC. Filling CO2 would exceed it many times over, and the pressure relief, compressor and oil are wrong. Propane in an HFC system puts a flammable refrigerant in equipment never assessed for ignition sources, the room may not meet the charge limits, and the plant no longer matches its CE marking ^[3][5]. In practice you therefore build a new system or replace the unit, reusing at most cabling and some cooling points if the manufacturer approves.

What replaces R404A?

R404A has a GWP of about 3,900. Since 1 January 2025 virgin R404A may not be used to service refrigeration equipment; reclaimed or recycled R404A may be used until 31 December 2029, and from 1 January 2032 the service limit for stationary refrigeration falls to GWP 750 ^[1]. An existing plant is usually converted to an HFC/HFO blend, while a new plant is built for R744 or R290. The table compares the common choices; GWP as in Regulation (EU) 2024/573 ^[1], glide calculated with CoolProp at a dew point of −30 °C ^[7].

• R448A, R449A and R452A are A1 like R404A, so the safety class does not change. Their GWP is below 2,500 but above 750, so after 2031 they too may only be topped up with reclaimed or recycled gas ^[1].
• R454C and R455A have a GWP below 150 but are A2L (mildly flammable). Converting an A1 plant to them needs a new EN 378 assessment of charge limits, ventilation and components ^[3].
• R404A and the blends above run on POE oil. Check the compressor maker's approval for the new refrigerant and the oil before you convert.
• The blends have a temperature glide of 4–14 K. Measure superheat from the dew point and subcooling from the bubble point, as the superheat guide describes.
• The retrofit calculator compares capacity, discharge temperature and mass flow of these refrigerants for your plant.

Step 1: Plan the new system

1. Work out the cooling load per temperature level (medium, low, air conditioning) and over the year, and any heat recovery needs.
2. Choose the system concept. A transcritical CO2 booster serves medium and low temperature in one system. An indirect system with a propane chiller keeps the propane outdoors or in a machinery room and distributes cold with a secondary fluid such as glycol or CO2 brine. Plug-in cabinets with R290 (self-contained, often water-cooled) suit smaller shops.
3. Decide where refrigerant-containing parts go: in the occupied space, in a machinery room, outdoors or in a ventilated enclosure. This gives the location class and the access category ^[3][4].
4. Size the pipework. The CO2 calculator sizes copper and steel pipes for R744, and the HC calculator checks the charge limit for R290 and other hydrocarbons.

Step 2: Safety class and charge limits

Under EN 378-1 and ISO 5149-1 the maximum charge depends on the refrigerant, the volume of the room, the location class and the access category ^[3][4]. For R744 (A1) the practical limit applies: if all of the charge leaks into the smallest room, the concentration must stay below the limit, otherwise measures such as gas detection, ventilation or a machinery room are needed. CO2 is heavier than air and collects at floor level.

For R290 (A3) the limits are based on the lower flammability limit (LFL). Below m1 there are essentially no room-dependent requirements, between m1 and m3 the room size and installation height limit the charge, and above m3 the refrigerant-containing parts must be in a machinery room, a ventilated enclosure or outdoors ^[3]. Take the exact values and formulas from the edition of the standard that applies to the project. The article on flammable refrigerants shows examples for propane.

Step 3: Pressure, PED and ATEX

Each part must have a PS that covers the highest pressure in operation, at standstill and during transport ^[3]. For CO2, check the standstill pressure: many systems have a small standstill cooling unit, or vessels rated to withstand it. Under the Pressure Equipment Directive 2014/68/EU the category (I–IV) depends on PS, volume or pipe size and the fluid group. Propane is group 1, CO2 group 2, and the category decides the conformity assessment and whether a notified body is needed ^[5].

Where propane can form an explosive atmosphere, for example in a machinery room or during servicing, the employer must assess the risk, divide areas into zones and document it in an explosion protection document ^[6]. Equipment in a zone must be suitable for that zone under the ATEX equipment directive 2014/34/EU. EN 378 aims to avoid an explosive atmosphere in normal operation, but the risk must still be assessed.

Step 4: Competence and certification

Under (EU) 2024/573 and Implementing Regulation (EU) 2024/2215, the certificate requirement for installation, servicing, repair and decommissioning covers not only F-gases but also the alternatives ammonia, CO2 and hydrocarbons, and companies working for others must be certified ^[1][2]. The certificate types for persons are ^[2]:

Member States may issue combined certificates. Certificates under the old Regulation (EU) 2015/2067 correspond to the new types (category I → A1, II → A2, III → D, IV → E), but may only be used further if the holder has updated their knowledge through the training or assessment required by Article 10 of (EU) 2024/573 ^[1][2]. For a CO2 system the technicians therefore need type B, and for propane A1 or A2. Check the certificates of the installer and the service company before the contract.

Step 5: Decommission the HFC plant

The old refrigerant must be recovered by a certified person and sent for recycling, reclamation or destruction. Note the quantity in the records. Intentional release is prohibited ^[1].

Step 6: Pressure test, evacuate and commission

1. Strength test and tightness test the system with dry nitrogen according to EN 378-2 before it is charged. CO2 test pressures are much higher than for HFC: plan the danger zone. See the pressure testing guide.
2. Evacuate and check with a standing vacuum test. See the guide to evacuation.
3. Charge the refrigerant. For CO2, break the vacuum with vapour first so that dry ice does not form. For propane, keep ignition sources away and measure with a gas detector intended for it.
4. Test safety functions: pressure limiters, safety valves, gas detection, alarms, ventilation and emergency stop.
5. Check the operating data and train the operator.

Documentation

• Declaration of conformity and CE marking of the assembly under the PED, with the category and the conformity assessment ^[5].
• Pressure test and tightness test certificates, charge and refrigerant on the nameplate.
• Risk assessment, charge limit calculation and, for propane, the explosion protection document ^[3][6].
• Operating instructions, logbook and the certificates of those who did the work ^[2].

Checklist

• Is the reason for the switch clear: service ban, product ban, leaks or cost?
• Is the cooling load per temperature level known?
• Has the system concept been chosen: CO2 booster, propane chiller with secondary fluid or plug-in?
• Have the location class and access category been decided for every refrigerant-containing part?
• Has the charge limit been checked against the applicable edition of EN 378 or ISO 5149?
• Have PS, PED category and conformity assessment been decided?
• For propane: has the ATEX risk assessment and zoning been done?
• Do the persons and the company hold certificates for CO2 or hydrocarbons?
• Has the HFC been recovered and recorded?
• Have the pressure test, evacuation and function tests been documented?