R22 was banned from service use in the UK in 2015. For the millions of commercial AC, heat pump and chiller systems designed around R22, R407C became the standard retrofit solution. This guide covers the complete R22 to R407C conversion process, what can go wrong, and how to do it right the first time.
Why R22 Was Banned and What It Means for Existing Systems
R22 (chlorodifluoromethane, HCFC-22) was the dominant refrigerant in commercial AC systems from the 1960s through to the early 2000s. Its ozone depletion potential (ODP 0.055) led to its phase-out under the Montreal Protocol. The UK timeline:
- 2004: R22 banned from use in new equipment in the EU/UK
- 2010: Virgin (newly manufactured) R22 banned from service use
- 2015: All R22 — including recycled and reclaimed stock — banned from service use
The result: any R22 system still running must either be retrofitted to an approved alternative or decommissioned. R22 cannot legally be purchased or used for service in the UK.
Why R407C Is the Standard R22 Retrofit
R407C (a blend of R32 23% / R125 25% / R134a 52%) was specifically formulated to match R22’s thermodynamic performance as closely as possible in an HFC blend. Key compatibility factors:
- Similar capacity: R407C delivers approximately equivalent cooling and heating capacity to R22 in most system configurations
- Similar operating pressures: R407C discharge and suction pressures are close enough to R22 that existing pipe runs, pressure vessels and most components remain suitable
- Non-flammable: A1 safety rating — no additional safety measures required beyond standard good practice
- Same expansion device compatibility: TXV and fixed-orifice expansion devices designed for R22 typically work with R407C after reselection/adjustment
The R22 to R407C Conversion: Step-by-Step
Converting an R22 system to R407C is not a drop-in replacement. The following steps are essential for a successful, compliant conversion:
Step 1: Recover All R22
All existing R22 must be recovered using a certified refrigerant recovery machine. R22 cannot be vented to atmosphere — this is a criminal offence under UK F-Gas and ozone regulations. Recovered R22 must be sent for reclaim or destruction via an authorised waste handler.
Step 2: Oil Change — Mineral to POE
This is the most critical step. R22 systems use mineral oil (or sometimes alkylbenzene oil), which is not compatible with R407C. R407C requires POE (polyolester) oil for proper lubrication and oil circulation. The mineral oil must be thoroughly flushed and replaced. Multiple oil changes may be required to ensure residual mineral oil contamination is below 5% — confirm with the compressor manufacturer’s specification.
Select the correct POE viscosity grade per the compressor manufacturer’s R407C retrofit guidance — typically ISO VG 32 or ISO VG 68 depending on the application.
Step 3: Replace Filter-Drier
The existing filter-drier must be replaced with one approved for use with R407C and POE oils. POE oil is hygroscopic and more sensitive to moisture contamination than mineral oil — a fresh, correctly rated drier is essential.
Step 4: Check Seals and Gaskets
R407C is compatible with most existing seals and gaskets used in R22 systems, but inspect all elastomeric seals for condition. Aged or cracked seals should be replaced before charging.
Step 5: Charge with R407C as Liquid
R407C must always be charged as a liquid, not as a gas. R407C is a zeotropic blend with a temperature glide of approximately 7°C — the three components evaporate at different rates. Charging as gas causes composition shift, delivering a non-standard blend into the system. Always invert the cylinder or use liquid charging equipment to draw liquid refrigerant.
Charge the system to the manufacturer’s specified weight for R407C (this may differ from the original R22 charge weight by 5–10%).
Step 6: Commission and Record
Commission the system, verify superheat and subcooling against R407C target values (not R22 targets), check for leaks, and update the equipment’s refrigerant type label. Under UK F-Gas regulations, operators of systems above 5 tCO₂e must maintain refrigerant records and schedule regular leak checks.
Temperature Glide: The Practical Impact
R407C’s temperature glide (~7°C) means the refrigerant temperature changes during boiling and condensing. This has two practical implications:
- Superheat and subcooling targets differ from R22 — use R407C-specific pressure-temperature charts and manufacturer commissioning data
- Charging method: always liquid-charge to maintain correct blend composition (see Step 5 above)
Buying R407C in the UK
Refrigerant Gas Supplies Ltd supplies R407C in 10 kg refillable cylinders for F-Gas Category I certified engineers. Next-day mainland UK delivery. For new installations, see our R32 9 kg cylinder — the current UK standard. Browse our full refrigerant gas range.
Frequently Asked Questions
Can I simply swap R22 for R407C without changing the oil?
No. R22 systems use mineral oil, which is incompatible with R407C. The oil must be changed to POE before charging. Skipping this step causes compressor damage and poor system performance.
Why must R407C be charged as a liquid?
R407C is a zeotropic blend with ~7°C temperature glide. Charging as gas causes composition shift — the blend ratio entering the system will be wrong. Always charge liquid to maintain correct composition.
Can I mix R407C with R22?
No. Mixing is illegal under UK F-Gas regulations and creates an unknown blend. All R22 must be fully recovered before R407C is introduced. R22 cannot be vented to atmosphere.
Is R407C still available in the UK?
Yes. Refrigerant Gas Supplies Ltd stocks R407C in 10 kg refillable cylinders with next-day UK delivery. F-Gas Category I certification required. Order R407C online.