R-437A PT Chart and Refrigerant Profile

Where you will find R-437A

R-437A is Chemours’ Freon MO49 Plus (ISCEON MO49 Plus under DuPont): an HFC blend of R-134a and R-125 with small amounts of butane and pentane. It is a retrofit refrigerant for R-12 equipment, and Chemours also lists it for systems on the HCFC service blends R-401A, R-401B and R-409A. It also took over from R-413A (ISCEON MO49), whose production ended.

Chemours’ bulletin lists medium- and high-temperature refrigeration built for R-12: food service, supermarket display cases, food storage and processing, and domestic refrigerators and freezers. It does not recommend R-437A for centrifugal machines, chillers or flooded evaporators. BITZER gives an application range of about 54°F to -22°F (12 to -30°C).

Chemours, Linde and A-Gas also market it for R-12 vehicle A/C, but it is not on EPA’s SNAP list for motor vehicle air conditioning. That marketing applies outside the US.

Look for a retrofit tag reading R-437A or MO49 Plus on an R-12 era system. The legacy cylinder color assigned in AHRI Guideline N-2017 was royal blue; containers made since 2020 are light green-gray.

Charging R-437A

R-437A is a zeotropic blend. The computed glide at 40°F evaporating is 5.2°F. A-Gas says it must be charged from the liquid phase. Chemours says an existing MO49 Plus system can be topped off after a leak, as long as you charge liquid. Meter the liquid slowly so it flashes before the compressor.

No first-party charge percentage against R-12 was found, so weigh in according to the retrofit procedure or the equipment maker. Read suction pressure against the dew column for superheat with the superheat calculator. On TXV systems, charge by subcooling to the manufacturer’s target with the subcooling calculator, using the bubble column.

The low side reads near R-12; the high side does not. On this site’s tables R-437A reads 41.2 psig at a 40°F dew point against 36.9 psig for R-12 at 40°F. At a 100°F bubble point it reads 148.9 psig against 116.9 psig for R-12. Do not charge to R-12 head pressures.

Oil and compatibility

The selling point is oil. Chemours says R-437A works with mineral oil, alkylbenzene and POE (and PAG in automotive A/C), and that in most cases no lubricant change is needed. It adds that a small amount of PAG may help oil return in R-12 vehicle retrofits. A-Gas says it works with most current oils but returns oil better with POE.

BITZER is more cautious: it lists POE and PVE, with AB only “with limitations”. The compressor maker’s approval decides. The refrigerant oil types guide compares the families.

Recover the old refrigerant completely before charging R-437A. Mixing it with R-12 or an HCFC blend gives a charge that matches no chart.

Safety, handling and recovery

R-437A is A1: lower toxicity, no flame propagation. ODP is 0. It is a non-exempt substitute: venting is prohibited, required recovery levels apply, and since Jan 1 2018 sales are restricted to certified technicians (40 CFR 82.154(c)).

40 CFR 82.152 does not name R-437A, so its class comes from the 104°F liquid saturation pressure. This site’s table gives 158.5 psig (173.2 psia) at 104°F bubble, just above the 170 psia line, which makes it a high-pressure refrigerant by the definition. Small appliances need Type I certification, other equipment Type II; Universal covers both.

From Jan 1 2026 the HFC leak-repair rule (40 CFR 84.106) applies to appliances with 15 lb or more of charge outside residential and light commercial AC. See refrigerant leak repair rules.

Status and replacements

R-437A is an HFC blend under the AIM Act phasedown (40 CFR 84.7): allowances 60% of baseline in 2024-2028, 30% in 2029-2033, 20% in 2034-2035 and 15% from 2036. Its EPA-basis GWP of 1,805 is above the Technology Transitions limits for new equipment in nearly every sector it served. 40 CFR 84.54 also names it for large self-contained ice machines and food processing and dispensing equipment from Jan 1 2027. Servicing existing equipment remains legal. From Jan 1 2029, servicing supermarket systems, refrigerated transport and automatic commercial ice makers must use reclaimed HFC.

No source names a successor to R-437A. For the low-GWP options in R-12 and R-134a type equipment, see R-513A, R-450A and the R-134a replacement guide. Current US sales of MO49 Plus by Chemours could not be confirmed.

Common questions

Is R-437A the same as R-134a?

No. It is about 78.5% R-134a, plus R-125 and hydrocarbons. It runs a higher head pressure than R-134a and has glide, so it needs its own PT chart and liquid charging.