Retrofit A1 to A2L: The Complete Solution for Your Refrigeration Systems

Introduction

Retrofitting a refrigeration system — replacing the original refrigerant with a different one — is an increasingly common operation in the context of the F-gas Regulation and the transition to low-GWP (Global Warming Potential) fluids. For refrigeration installers and maintenance contractors, mastering this operation according to best practice is essential: personnel safety, regulatory compliance, and system performance are all at stake.

This article outlines the complete retrofit procedure for a system originally designed for an A1 fluid (non-flammable, Pressure Group 2) to an A2L fluid (mildly flammable, Pressure Group 1), in compliance with the European DESP Directive 2014/68/EU, the F-gas Regulation 2024/573, the arrêté of 25 June 1980 (CH35), the EN-378 standard, and the relevant professional reference guides.

1. What Is a Retrofit? Definition and Challenges

A retrofit consists of replacing the refrigerant contained in a refrigeration system with a fluid different from that originally intended by the manufacturer. This operation may be driven by:

• The F-gas 2024/573 regulation and the gradual reduction of HFCs (hydrofluorocarbons)
• The unavailability or rising cost of traditional A1 fluids (R-404A, R-410A, R-134a)
• The desire to reduce the carbon footprint of the installation
• Compliance with new environmental requirements

⚠️ Important note: a retrofit is not a simple recharge. It is a technical modification that engages the installer’s responsibility and requires adherence to a strict regulatory framework. Switching from an A1 fluid (Pressure Group 2) to an A2L fluid (Pressure Group 1) is a sensitive operation that requires a full safety assessment of the installation.

2. Applicable Regulations for Retrofit

2.1 The European DESP Directive 2014/68/EU — The Central Pillar

The European Directive 2014/68/EU on pressure equipment (DESP — Directive Équipements Sous Pression) is the fundamental text governing retrofit. It defines what constitutes a significant modification and requires the full system to be re-evaluated.

Why DESP takes precedence over the refrigeration CTP?

The refrigeration CTP (Cahier des Charges Particulier) is a professional document governing in-service monitoring of installations. But before entering the CTP framework, any retrofit must first satisfy the requirements of the DESP Directive 2014/68/EU. It is the DESP that defines whether the operation is a significant modification, imposes the conformity assessment, and determines whether a Notified Body (NB) must intervene.

DESP scenarios:

Note 1: Changing to a fluid listed in the technical documentation (for example an alternative fluid specified by the manufacturer) is not considered a modification under the DESP.

Note 2: These provisions are not applicable to refrigeration systems monitored under the “Refrigeration System” CTP.

Mandatory safety assessment:

For any significant retrofit, the refrigeration system and the installation must be re-evaluated under Directive 2014/68/EU to safely admit the refrigerant into the installation. This assessment covers:

2.2 The F-gas Regulation 2024/573

Regulation (EU) 2024/573 (which replaces Regulation 517/2014) mandates the gradual reduction of greenhouse-gas fluid use in refrigeration equipment. High-GWP A1 fluids (R-404A, R-507, R-410A) are subject to decreasing production quotas, making their price prohibitive and availability uncertain.

Retrofit to A2L fluids (R-32, R-454B, R-454C, R-455A, etc.) is a direct technical response to this regulatory constraint. This regulation notably governs:

• Mandatory recovery of removed fluids
• Operator certification
• Fluid traceability
• Progressive bans on certain substances

2.3 The Arrêté of 25 June 1980 — Article CH35 (ERP)

The arrêté of 25 June 1980 approving the general provisions of the safety regulation against fire and panic risks in establishments receiving the public (établissements recevant du public, ERP) contains Article CH35, which specifically governs installations using refrigerant fluids.

Key definitions (CH35):

• Flammable refrigerants: fluids that propagate a flame at 60°C and 101.3 kPa
• Toxic refrigerants: fluids with evidence of toxicity at concentrations below 400 ppm
• Thermodynamic system: interconnected parts (piping, fittings, units) containing the fluid in a closed circuit
• Machine room: enclosed space or closed area isolated from public spaces intended to contain the system components

Provisions applicable regardless of fluid (§2):

• Compressor-equipped units placed in publicly accessible rooms must be hermetic or accessible-hermetic type
• The machine room must have at least two ventilation openings to the outside, located at different heights
• The machine room is a common-risk room
• Piping carrying refrigerant fluids must be metallic
• Thermal insulation must be classified M1 or CL-s3,d0 in public rooms, M3 or DL-s3,d0 elsewhere

Specific provisions for flammable fluids (§3):

Section 3 of Article CH35 strictly governs installations using flammable refrigerant fluids such as A2L:

a) Exclusion zone:

An exclusion zone is established around the removable or non-removable fittings (excluding brazed and welded joints) of units containing flammable refrigerant fluids, in which the presence of any source capable of producing a flame or spark is prohibited in order to avoid any risk of ignition in the event of a leak.

Exclusion zone radii table:

Legend: LII = Lower Ignitability Limit (kg/m³); M = Molar mass (kg/mol); P = Maximum absolute pressure at condenser outlet (bar)

b) Maximum allowable charge quantity:

The total maximum quantity of flammable refrigerant circulating in the thermodynamic system that could be released is limited in order to avoid any risk of reaching the lower ignitability limit in the event of a leak in the room.

Calculation formula:

mmax = 2.5 × LII^(5/4) × h0 × A^(1/2)

With:

• mmax (kg): total maximum quantity of flammable refrigerant
• LII (kg/m³): lower ignitability limit
• h0: coefficient related to the height of the lowest equipment in the room:
  • 0.6 for floor-mounted installation
  • 1.1 for window-mounted installation
  • 1.8 for wall-mounted installation
  • 2.2 for ceiling-mounted installation
  • Height of the lowest connection if > 2.2 m
• A (m²): room surface area

Machine rooms — No charge restriction IF:

• Detection device that, in case of a leak, triggers the mechanical air extractor and cuts off fluid circulation
• Two sensors adapted to the fluid nature + detection control panel
• Automatic failure alarm for the detection/extraction system
• Mechanical air extractor of category 3 (Directive 2014/34/EU)
• Compliance with EN 378 standard is deemed to satisfy these requirements

Other rooms and circulation areas — No charge restriction IF:

• Early leak detection system
• Interlocked device ensuring closure of the refrigeration circuit and forced mixing of the volume
• Hermetic closure, connected by welding or brazing
• Compliance with EN 378 standard is deemed to satisfy these requirements
• Derogation: removable fittings permitted in a technical room with detection + extraction

Ventilation:

• Exhaust to the outside (compliant with Articles CH 28 to CH 43)
• Ventilation ducts and enclosures REI 30
• Mechanical extractor of category 3 (Directive 2014/34/EU)

c) Installation document:

A document describing the installation must be available for the administrative authorities and the companies intervening. This document includes:

• A piping network plan
• A system schematic
• A detailed calculation of the maximum quantities of fluids used
• A layout plan of the safety devices (detectors, solenoid valves, ventilation, etc.)
• The theoretical ventilation flow rates in case the maximum calculated quantity is exceeded
• A description of the detection devices (calibration, reliability, response time, etc.)

This document is updated after any modification of the installations or premises.

Conseil d’État ruling of 19 July 2023:

By decision No. 435581, the Conseil d’État annulled the arrêté of 10 May 2019 insofar as the provisions of the new paragraph 3 (with the exception of points a and c) apply to equipment bearing CE marking that is not hermetically sealed.

2.4 The EN-378 Standard

The EN-378 standard defines the safety requirements for refrigeration systems, notably regarding fluid charge limitation and protection against flammability risks.

For an A1 → A2L retrofit, EN-378 requires:

• Calculation of the maximum allowable charge: the quantity of A2L fluid in the installation is limited according to the machine volume, ventilation, and room occupancy
• Room classification: determination of safety zones according to leak risk
• Safety devices: leak detectors, alarms, forced ventilation according to charge and classification
• Minimum distance to ignition sources: compliance with regulatory distances between equipment and electrical appliances

Compliance with the provisions of EN-378 standard regarding air renewal rates is deemed to satisfy the requirements of Article CH35 for machine rooms.

2.5 Professional Guides

Two reference documents govern retrofit in France:

• The AFCE practice sheet (July 2024): methodological guide in 4 steps for A1 → A2L/G1 retrofit, with checkpoints and the evaluation procedure
• The AQUAP 99/13 guide: technical reference for operations on pressure equipment, including significant modification criteria

3. The 4 Steps of Retrofit according to the AFCE Sheet

Step #01: Preamble

Retrofitting an existing installation with a mildly flammable fluid (A2L) is not prohibited, but requires following important feasibility steps.

Key points:

• Replacing a Pressure Group 2 fluid with a Pressure Group 1 fluid = significant modification without test according to the AQUAP 99/13 guide
• Often a Notified Body (NB) is required, with a technical intermediary such as DCRR that prepares and supports the dossier
• The retrofit engages the installer’s responsibility across the entire compliance chain

Reference documents: Arrêté of 20/11/2017 + CTP SF | AQUAP 99/13 Guide

Step #02: Regulatory Feasibility Study

The risk analysis of the modified system according to applicable regulations includes:

1. Formalisation of input data: fluid choice, ambient conditions, access category, etc.
2. Verification of risk categories: does the fluid change modify the risk categories of the pressure equipment?
3. Conformity of the EXISTING system: ESP in-service verification, F-Gas Regulation, Environmental Code
4. Conformity of the MODIFIED system: application of new regulatory requirements
5. Calculation of the maximum allowable charge: determination of the A2L fluid limit quantity according to CH35 and EN-378
6. Consultation of a Notified Body (NB): BV, APAVE, ASAP, TECNEA or other Notified Body for DESP, with the support of a technical intermediary such as DCRR to prepare the dossier

Reference documents: Specification | Risk Analysis Guide (UNICLIMA, CETIM, SNEFCCA, EN 378) | CTP SF | Environmental Code | Arrêté of 20/11/2017 | System Register | Regulation 2024/573 (F-Gas) | EN 378-1

Step #03: Technical Feasibility Study

The technical risk analysis of the modified system according to applicable regulations includes:

1. Formalisation of technical data: cooling capacity, power consumption, efficiency, etc.
2. Compatibility assessment: equipment and accessories compatible with the new fluid (oil, pressure, temperature)
3. Component selection: expansion valve, accessories, materials suited to the chosen A2L fluid
4. Component condition check: cleanliness, corrosion, thermal insulation of the existing system
5. Parameter verification and correction: automated regulation and supervision to be reparametered for the new fluid

Reference documents: Specification

Step #04: Implementation

For systems subject to the ministerial arrêté of 20/11/2017:

Before intervention:

• Creation of a significant intervention dossier
• Transmission to a Notified Body (NB) or qualified body
• Support from a technical intermediary such as DCRR to prepare the dossier
• Preparation of tools and equipment adapted to A2L fluids:
  • Electrically protected vacuum pumps
  • Hermetic transfer units
  • Leak detectors adapted to A2L
  • Personal protective equipment

On-site operations:

• Recovery and treatment of the existing fluid (mandatory F-gas destruction certificate)
• Recovery and treatment of the oil (incompatible with the new fluid)
• Installation of compatible components (gaskets, expansion valve, accessories)
• Tightness test (without hydraulic test if Group 2 non-corrosive)
• Testing of safety devices (pressure switches, relief valves, detectors)
• Commissioning and adjustments

Final documentation:

• Recording of settings and operating readings
• Modification/verification of labelling:
  • CE marking
  • Fluorinated (if applicable)
  • A2L fluid
• Completion of the instruction manual
• Update of the monitoring register
• Update of the operating dossier
• Information to the client on their obligations (CTP SF, F-GAS 2024/573)

Reference documents:

• Intervention compliant with essential safety requirements (Articles R. 557-9-4)
• Significant intervention dossier according to Art. 28 of the arrêté of 20/11/2017 + AQUAP ESX 18 sheet
• EN 378 | Environmental Code | (EU) 2024/573 | Arrêté of 20/11/2017 + CTP SF

4. Charge Calculation according to CH35 and EN-378

Charge calculation is a critical step of the A2L retrofit. It determines the maximum quantity of fluid that can be safely used in a given room.

4.1 Article CH35 Formula

mmax = 2.5 × LII^(5/4) × h0 × A^(1/2)

Variables:

• mmax (kg): total maximum quantity of flammable refrigerant
• LII (kg/m³): lower ignitability limit of the fluid
• h0: height coefficient:
  • 0.6: floor-mounted installation
  • 1.1: window-mounted installation
  • 1.8: wall-mounted installation
  • 2.2: ceiling-mounted installation
  • Height of the lowest connection if > 2.2 m
• A (m²): room surface area

4.2 Calculation Example

Take a technical room of 20 m² with a floor-mounted refrigeration unit (h0 = 0.6) using R-32 (LII ≈ 0.307 kg/m³):

mmax = 2.5 × (0.307)^(5/4) × 0.6 × (20)^(1/2) mmax = 2.5 × 0.226 × 0.6 × 4.47 mmax ≈ 1.52 kg

If the charge required for the installation exceeds 1.52 kg, compensatory measures are mandatory:

• Installation in a machine room with detection + mechanical extraction
• Or installation of an early detection system with automatic circuit closure

4.3 Maximum Charges Summary Table

Indicative values to be verified against exact manufacturer data

5. A2L Fluids: Characteristics and Precautions

A2L (mildly flammable) fluids present a limited but real flammability risk. Their use requires specific precautions:

• Ventilation: ensure adequate dispersion in case of a leak
• Leak detectors: mandatory installation according to charge and room type
• Ignition sources: keep away non-compliant electrical equipment
• Trained personnel: handling by technicians certified for flammable fluids
• Exclusion zone: compliance with the radii defined in the CH35 table

Most common A2L fluids in retrofit:

6. FAQ — A1 to A2L Retrofit

Q: Is an A1 to A2L retrofit always considered a significant modification?

A: Yes, as long as the replacement fluid is not listed in the original technical documentation. If the fluid is listed as an alternative by the manufacturer, the operation is not a modification. Switching from a Pressure Group 2 fluid to a Pressure Group 1 fluid is a significant modification without test according to the AQUAP 99/13 guide.

Q: Is a hydraulic test required during a retrofit?

A: No, if the replacement fluid belongs to Group 2 non-corrosive with respect to the equipment walls. A tightness test is sufficient. This is the case for most A2L fluids.

Q: What is the difference between an A1 fluid and an A2L fluid?

A: An A1 fluid is non-flammable (no ignition risk). An A2L fluid is mildly flammable: it can ignite but its combustion speed is slow. This requires ventilation precautions, exclusion zones, and leak detectors.

Q: Does the F-gas Regulation mandate retrofit?

A: The F-gas Regulation 2024/573 does not directly mandate retrofit, but it drastically reduces HFC (A1 fluid) quotas, making their price prohibitive. Retrofit to A2L fluids then becomes the economically viable solution.

Q: Who can perform an A1 to A2L retrofit?

A: The operation must be carried out by a certified refrigeration installer or maintenance contractor, with training on flammable fluids (A2L), suitable recovery equipment, and F-gas certification.

Q: Does Article CH35 apply to all buildings?

A: Article CH35 applies to establishments receiving the public (établissements recevant du public, ERP). For other buildings (very small ERP, residential premises, industrial premises), other regulations may apply, but the safety principles remain the same.

Q: What should be done if the calculated charge exceeds the maximum allowable charge?

A: If the CH35 calculation shows that the required charge exceeds mmax, several solutions exist:

• Install the system in a machine room with detection and mechanical extraction
• Install an early detection system with automatic circuit closure
• Reduce the charge by splitting the installation (split)
• Choose a fluid with a higher LII

7. Conclusion

The A1 to A2L retrofit is a complex technical and regulatory operation that engages the installer’s responsibility across the entire compliance chain. The European DESP Directive 2014/68/EU is the central pillar of this approach: it defines the significant modification, requires the re-evaluation of the installation, and determines the role of the Notified Body (NB), often supported by a technical intermediary such as DCRR to prepare and structure the dossier.

Article CH35 of the arrêté of 25 June 1980 provides the specific fire safety requirements for flammable fluids, notably the maximum charge calculation, exclusion zones, and detection systems. The EN-378 standard complements this framework with the technical design and installation requirements.

With the increasing pressure of the F-gas Regulation 2024/573 and the scarcity of traditional A1 fluids, this competence is becoming indispensable for refrigeration installers and maintenance contractors.

DCRR supports refrigeration professionals in this transition. Our regulatory expertise and our tools (cDESP, PV ESP) enable you to document and trace each step of the retrofit in compliance with DESP, EN-378, CH35, and the refrigeration CTP.

👉 Contact us for retrofit support

References: AFCE Practice Sheet — Retrofit A1→A2L/G1 (July 2024) — AQUAP 99/13 Guide — Directive 2014/68/EU (DESP) — Regulation (EU) 2024/573 (F-gas) — Arrêté of 25 June 1980 (CH35) — EN-378 — DCRR