R-422B Refrigerant: What It Is, How It Runs, and What Section 608 Says

R-422B is a three-part HFC blend of 55% R-125, 42% R-134a and 3% R-600a (isobutane), sold as NU-22B and ICOR XAC1. EPA's SNAP program lists it as an acceptable retrofit and new-equipment substitute for R-22 in residential and light commercial air conditioning, with ASHRAE class A1 and a GWP of 2,530. It has zero ozone depletion potential. It is not a true drop-in.

Most of the pages that rank for R-422B are distributor listings, a safety data sheet and a PT chart. They tell you what is in the cylinder and where to buy it. They rarely tell you why your gauges read differently than they did on R-22, or that a blend with no chlorine moves the system out of one leak repair rule and into another. This article covers both, and it marks which parts are regulation and which are good practice.

What is R-422B refrigerant?

R-422B is a zeotropic blend designed to approximate R-22 in air conditioning. Each component does a job. R-125 and R-134a carry the capacity. The small isobutane share is there, as in R-422D and R-438A, to help oil keep moving with the mineral oil already in an older R-22 system.

Property	R-422B	R-22
Composition	55% R-125 / 42% R-134a / 3% R-600a	Single compound (HCFC-22)
Trade names	NU-22B, ICOR XAC1	—
ASHRAE 34 safety group	A1	A1
GWP (EPA SNAP listing)	2,530	—
Ozone depletion potential	0	Not zero (HCFC)
Temperature glide	Yes, several degrees	None
Boiling point at 0 psig	−42.4 °F	—
SNAP status, residential and light commercial AC	Acceptable, retrofit and new, listed March 29, 2006	Phased out of production and import

The SNAP row comes from EPA's residential and light commercial air conditioning substitutes list. Composition, boiling point and safety rating are from the Hudson Technologies R-422B PT chart.

What does R-422B replace?

R-22, in air conditioning. That is its design brief. Do not confuse it with its sibling R-422D, a different blend sold as ISCEON MO29 with its own pressures and a SNAP-listed GWP of 2,730. Both are listed by SNAP, and they are not interchangeable.

R-22 itself has not been produced or imported since January 1, 2020, but servicing existing R-22 equipment is still legal. Our guide to whether R-22 is still available covers that. R-422B exists for the owner who wants to keep an old condenser running without paying for reclaimed R-22. Producers describe a slight capacity reduction against R-22, which shows up as longer run times. Whether that is acceptable on a given system is a manufacturer and owner decision, not a cylinder-label decision. The R-22 replacement refrigerant guide compares R-422B with the other SNAP-listed options.

What are the actual R-422B pressures?

R-422B is a blend with glide, so its chart prints two columns: liquid (bubble point) and vapor (dew point). Values below are psig, from the Hudson chart, with R-22 for comparison from the figures in our R-22 PT chart.

Temperature	R-422B liquid (bubble)	R-422B vapor (dew)	R-22
20 °F	43.9	35.5	43.1
30 °F	55.9	46.6	—
40 °F	69.6	59.4	68.6
50 °F	85.3	74.1	84.1
90 °F	170.0	156.0	168.4
100 °F	198.0	183.0	195.9
110 °F	229.0	213.0	226.4
120 °F	263.0	247.0	—

The column that matters on the low side is vapor. At a 40 °F evaporator, R-22 reads about 69 psig; R-422B's dew point reads about 59 psig. Read an R-422B system against an R-22 chart and a correct charge looks about 10 psi short on suction.

Why does R-422B have temperature glide?

Because its three components boil at different temperatures. As the blend evaporates, the lower-boiling parts leave the liquid first, so the temperature rises across the evaporator at constant pressure. That spread is the glide.

You can read it off the chart. At 69.6 psig, the liquid column says 40 °F. The vapor column passes 69.6 psig between 45 °F (66.5) and 50 °F (74.1), at roughly 47 °F. That is about 7 °F of glide at a typical evaporator pressure, and somewhat less on the high side. Published glide figures for R-422B vary between sources, so use the producer's own chart rather than a number quoted on a forum.

Glide is why the column choice matters:

Calculation	Pressure you read	Column you use
Superheat	Suction	Vapor (dew point)
Subcooling	Liquid line	Liquid (bubble point)

Mixing up the columns gives you a superheat number that is several degrees wrong. Our superheat and subcooling guide covers how to read each one.

How do you charge R-422B?

As liquid, unless the producer's instructions say otherwise. Taking vapor off the top of a zeotropic blend cylinder draws off the lower-boiling components first and changes the composition of what goes into the system and what stays in the cylinder. Liquid charging, throttled so liquid does not slug the compressor, keeps the blend as designed.

That is manufacturer instruction and good practice, not a Section 608 rule. So are the other retrofit steps: checking the metering device, replacing the filter drier, deciding whether the oil needs to change, and labeling the unit with the refrigerant and oil now in it. Follow the producer's retrofit guide and the equipment manufacturer's literature.

What does Section 608 require on an R-422B system?

More than its HFC status suggests, and less than an R-22 system.

Item	Status	Source
No knowing venting during service or disposal	Regulation	40 CFR 82.154(a)
Sold only to certified technicians and the other buyers the rule lists	Regulation	40 CFR 82.154(c)
Recover to Table 1 levels with certified recovery equipment	Regulation	40 CFR 82.156
November 15, 1993 cut-off in Table 1	Refers to the recovery machine's manufacture date, not the appliance	40 CFR 82.156
Section 608 leak repair (50 lb or more)	Does not apply. It covers Class I and Class II refrigerants, and R-422B contains no CFC or HCFC	40 CFR 82.157
AIM Act leak repair (15 lb or more of an HFC refrigerant)	Can apply	40 CFR 84.106
Evacuating to 500 microns before charging	Best practice, not a Section 608 requirement	Manufacturer instruction

The leak repair split is the part most pages miss. Once a system is converted from R-22 to R-422B, the Section 608 leak repair rule no longer reaches it. But EPA's AIM Act leak repair program, described in EPA's leak repair fact sheet, covers appliances holding 15 pounds or more of a refrigerant containing an HFC. Most residential splits sit below that line. Larger light commercial units may not.

Recovery is unchanged by the retrofit. Most R-422B equipment is a high-pressure appliance, which puts it under Type II, and a high-pressure appliance under 200 pounds must be recovered to 0 inches Hg on modern recovery equipment. Our recovery guide sets out the full table, and the Type II practice test is the quickest way to check you have it straight.

Does the AIM Act affect R-422B?

Yes, on supply. R-125 and R-134a are both regulated HFCs, and the AIM Act phase-down caps how much of them can be produced and imported. That puts upward pressure on the price of every high-GWP HFC blend, R-422B included. It does not ban servicing an R-422B system. Our AIM Act explainer covers where the Act binds a technician and where it does not.

What this means on the job

Look for the retrofit label first. An old R-22 condenser may hold R-22, R-422B, another blend, or a mix someone made. The gauges alone cannot tell you, and the wrong chart makes a good charge look bad.

Never top off with R-22. Adding R-22 to an R-422B system, or the reverse, creates a mixture no chart describes and no reclaimer wants. If you cannot identify what is in the system, recover it into a separate labeled cylinder.

Use the vapor column for superheat. That one habit prevents most R-422B overcharges.

Recover it into its own cylinder. R-422B recovered into an R-22 cylinder contaminates both. Label the cylinder with the blend.

Know which leak rule you are under. Converting a 60-pound R-22 system to R-422B swaps the 50-pound Section 608 rule for the 15-pound AIM Act rule. The obligation does not disappear; it moves.

The study guide covers the recovery, venting and sales rules the exam tests, and they apply to R-422B work the same day you pass.

Frequently asked questions

Is R-422B refrigerant still available?

Yes. R-422B is an HFC blend, not an HCFC, so the 2020 end of R-22 production does not touch it. EPA's SNAP list still shows it as acceptable for residential and light commercial air conditioning. Supply and price are shaped by the AIM Act phase-down of its R-125 and R-134a components, so expect cost to rise over time.

Is R-422B a drop-in replacement for R-22?

No. "Drop-in" has no regulatory meaning. R-422B runs at different pressures, has several degrees of glide and gives slightly less capacity than R-22. A retrofit usually means recovering the R-22, checking the metering device and drier, and following the producer's oil guidance. Label the system with the new refrigerant when you finish.

Can you mix R-422B with R-22?

You should not. Topping off an R-422B system with R-22, or the reverse, produces an unknown mixture that no PT chart describes and that cannot be reclaimed cleanly. If a system has already been mixed, recover the charge into a separate labeled cylinder, evacuate, and recharge with a single refrigerant.

What is the GWP of R-422B?

EPA's SNAP listing for residential and light commercial air conditioning gives R-422B a GWP of 2,530. Hudson Technologies' data sheet gives 2,525, a rounding difference. Either way, it is a high-GWP HFC blend, which is why the AIM Act phase-down affects its supply even though it has zero ozone depletion potential.

Do I need EPA 608 certification to buy R-422B?

Yes, in practice. Under 40 CFR 82.154(c), non-exempt substitute refrigerants, HFC blends included, may be sold only to certified technicians and the other buyers the rule lists. R-422B is a non-exempt substitute, so a supply house should ask for your Section 608 card before selling it.

Sources

• EPA SNAP, substitutes in residential and light commercial air conditioning and heat pumps
• 40 CFR 82.154, Prohibitions
• 40 CFR 82.156, Required practices
• 40 CFR 82.157, Appliance maintenance and leak repair
• 40 CFR 84.106, AIM Act leak repair
• EPA Emissions Reduction and Reclamation leak repair fact sheet
• Hudson Technologies R-422B pressure-temperature chart