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Refrigerants compared: R-410A, R-32, R-134a and ammonia
A refrigerant is just a fluid chosen because it boils and condenses at convenient temperatures when you squeeze it. Every one of them can move heat — they differ in the pressure they need to do it, how hot they leave the compressor, how dangerous they are, and how much damage they do if they escape.
The comparison
Pressures below are the saturation pressures at the temperatures a home system actually runs at: about 5 °C in the evaporator and 45 °C in the condenser. That's the key idea — you pick the operating temperatures, and the refrigerant decides what pressure you need to hit them.
| Refrigerant | Low side (5 °C evaporator) |
High side (45 °C condenser) |
Discharge temp | GWP | Safety |
|---|---|---|---|---|---|
| R-410APuron | 9.3 bar (120 psig) | 27.2 bar (380 psig) | ~80 °C | 2088× CO₂ | A1 — non-toxic, non-flammable |
| R-32difluoromethane | 9.5 bar (123 psig) | 28.5 bar (399 psig) | ~95 °C | 675× CO₂ | A2L — mildly flammable |
| R-134atetrafluoroethane | 3.5 bar (36 psig) | 11.6 bar (154 psig) | ~70 °C | 1430× CO₂ | A1 — non-toxic, non-flammable |
| R-717ammonia (NH₃) | 5.2 bar (61 psig) | 17.8 bar (243 psig) | ~120 °C | 0 — none | B2L — toxic, mildly flammable |
What the numbers actually mean
R-410A Puron
The standard in U.S. home AC & heat pumps (2000s–early 2020s).
Runs at high pressure. A blend being phased down because of its high global-warming potential.
R-32 difluoromethane
Newer split systems — the main replacement for R-410A.
About a third of R-410A's warming impact, but it runs noticeably hotter at the compressor.
R-134a tetrafluoroethane
Car AC, refrigerators, and chillers (older equipment).
Low, easy-to-handle pressures and a gentle discharge temp — but a high GWP, so it's being phased out.
R-717 ammonia (NH₃)
Industrial refrigeration — cold storage, food plants, ice rinks.
Extremely efficient with zero warming impact — but toxic and corrosive to copper, so it's never used in homes, and it runs very hot.
Why ammonia is the odd one out
R-717 is the most thermodynamically efficient of the bunch and has a global-warming potential of exactly zero — it's been used since the 1800s and still runs most of the world's cold storage, food plants, and ice rinks. So why isn't it in your house? Because it's toxic, it's corrosive to copper (so the whole system has to be steel), and it leaves the compressor at around 120 °C. Those are manageable problems in a plant room with trained staff and leak detection. They are not manageable in a closet next to your bedroom.
Why your system's refrigerant is changing
R-410A dominated U.S. homes for two decades, but with a GWP of 2,088 it's being phased down — a kilogram leaking out does the atmospheric damage of about two tonnes of CO₂. R-32 is the main replacement: roughly a third of the warming impact, slightly higher pressures, and a hotter compressor discharge. The trade-off is that it's classed A2L — mildly flammable — which is why newer equipment has different handling rules.
This matters for repairs. If you're weighing a compressor replacement on an aging R-410A system, the refrigerant phase-down is a real part of the repair-or-replace math.
A note on leaks
Whichever fluid you have, it runs in a sealed loop and is never consumed. If a tech says you're low, you have a leak — and topping it off without finding that leak vents a potent greenhouse gas straight into the atmosphere.