R-427A PT Chart and Refrigerant Profile

Where you will find R-427A

R-427A is an R-22 retrofit blend from Arkema, sold as Forane 427A and earlier as Forane FX100. It went into existing R-22 air conditioners and into medium- and low-temperature refrigeration that owners chose to keep running rather than replace (Arkema guidelines).

The nameplate on a converted system still says R-22. Look for the retrofit label, which should name R-427A and the oil now in the compressor. New cylinders are light green-gray (RAL 7044) like every refrigerant, so go by the label.

The blend is all HFC: R-32, R-125, R-143a and R-134a at 15/25/10/50 by mass. It has no ozone-depleting component, so the R-22 production and import ban does not apply to it.

Charging R-427A

Charge liquid only. R-427A is a four-component zeotropic blend; vapor drawn from the cylinder does not match its nominal composition. Arkema’s documents call for liquid charging and say not to mix R-427A with R-22, so recover every bit of R-22 before you charge.

For the starting charge, Arkema’s figures range from about 90% to 100% of the original R-22 charge weight: 95% in the retrofit guidelines, 95–100% in the retrofit procedure and 90% in the technical digest (Arkema digest). Start at the low end, then finish to superheat or subcooling.

The glide is large. At a 40°F dew point it is about 10.5°F, and at 40°F this chart shows 61.2 psig dew and 76.8 psig bubble. For comparison, R-22 saturates at 68.6 psig at 40°F, so an R-22 scale misreads both sides of an R-427A system. Set your gauges to R-427A or use the gauge lookup on this page.

• Superheat: convert suction pressure with the dew column. Fixed-orifice systems are charged to target superheat from CEC Title 24 Table RA3.2-2 (installer tolerance ±5°F, valid at 55–115°F outdoor, return dry bulb of 70°F or more, return wet bulb of 76°F or less). Use the target superheat calculator.
• Subcooling: convert liquid-line pressure with the bubble column and compare it with the manufacturer’s target on TXV systems, using the subcooling calculator.

The temperature glide calculator gives the glide at any pressure. Because of the glide, the coil inlet runs colder than the dew-point saturation temperature you use for superheat; that is normal.

Oil and compatibility

R-427A works best with POE. Arkema recommends replacing the mineral oil or alkylbenzene with POE, and says one oil change is usually enough. Its technical digest notes that a lubricant change may not be required in every case, but POE is always recommended.

Arkema’s retrofit guidance gets specific about when POE is needed:

• risers of about 20 ft or more
• long line sets
• an evaporator installed below the compressor

If an oil separator is fitted and oil return was good on R-22, Arkema says the original oil may be kept. BITZER says up to 15% residual mineral oil or AB is tolerated after the change (BITZER).

Replace the filter-drier during the retrofit, label the system with the refrigerant and oil, and evacuate to the OEM target, typically 350–500 microns (evacuation guide). POE absorbs moisture, so keep containers sealed. See the refrigerant oil guide.

Safety, handling and recovery

R-427A is ASHRAE class A1: lower toxicity and no flame propagation. Its pressures are in the R-22 range, so R-22-rated gauges, hoses and recovery cylinders are suitable.

Section 608 Type II (or Universal) certification covers R-427A systems, and only certified technicians may buy it. By the 40 CFR 82.152 definition it is a high-pressure refrigerant: its computed liquid saturation pressure at 104°F is 243.8 psia (229.1 psig, bubble). Recover appliances under 200 lb to 0 in Hg, and those of 200 lb or more to 10 in Hg.

Commercial refrigeration with 15 lb or more falls under the HFC leak-repair rule (40 CFR 84.106) from Jan 1 2026; residential and light commercial AC and heat pumps do not. Recover R-427A into its own labeled recovery cylinder (gray with a yellow top), never into one that holds R-22.

Status and replacements

EPA’s SNAP program listed R-427A as an acceptable R-22 substitute in residential and light commercial AC on Jan 2 2009 (EPA SNAP). Servicing and retrofitting existing systems with it remains legal.

Its GWP of 2,138 (AR4) is above the limits for new AC, heat pumps and commercial refrigeration under the Technology Transitions rule (40 CFR 84.54), and R-427A is named as restricted in new refrigerated food processing and dispensing equipment with more than 500 g of charge from Jan 1 2027. As an HFC blend, its supply falls under the AIM Act phasedown: 60% of baseline in 2024–2028, 30% in 2029–2033, 20% in 2034–2035 and 15% from 2036.

Other R-22 retrofit blends include R-407C, R-438A, R-422D, R-422B, R-417A and R-421A. Compare them in R-22 replacement refrigerants and see the R-22 phase-out guide.

Common questions

Can R-427A run on mineral oil?

Sometimes, but Arkema always recommends POE. The original oil may stay only where an oil separator is fitted and oil return was good on R-22. Change to POE with long lines, tall risers or an evaporator below the compressor.

R-427A vs R-22: what changes?

Pressures are in the same range as R-22, but R-427A has about 10°F of glide, must be charged as liquid, usually needs POE and must never be mixed with R-22.