Heat pump mini split question

difluoromethane is flammable:

What is the issue? Premature degradation? Mad Dog

R-32 and R-454B (a blend of R-32 and R1234yf) are what you will see in the US taking the place of R-410A. These are both classified as an "A2L" refrigerant, neither contains any propane, both are considered flammable. I would suggest you seek out an A2L seminar, or take the A2L course from the EPA test site. The flammability of the refrigerant is definitely something to take seriously as an installer, however the charge of a through the wall unit is likely too low to even require sensors anywhere. If you were to look at the flame propagation of an A2L compared to R-410A it is actually very close, but propagates flame just outside of the cone at the testing facility that separates a "non-flammable" refrigerant (which are still flammable mind you) from a flammable refrigerant. The A2L classification was created because while it is flammable it is not flammable enough to warrant being in the class 2 or 3, so there was a need to more accurately classify this lower flammability refrigerant.

If you are comfortable with natural gas or propane gas lines running through your house, which can obviously leak a lot more fuel, and fuel that is much more flammable. Then I would think R-32 or R-454B would not cause you too much distress. Manufacturers have had to spend a mountain of cash developing sensors and mitigation systems for their split systems connected to gas furnaces.

I guess I was wrong but just remembered that R-32 was flammable when I installed the new through the wall unit which is R-32.

I am long past keeping up on that stuff.

I long for the days of 12, 22 and 502.

That's strange

You might want to contact the manufacturers about their labeling then.

It literally says extremely flammable gas on it.

The UN classification is that it's flammable.

Here's R32

Here's Propane

Phosgene gas....that's what their big concern was back then. Mad Dog

You're spot on that R-290 is propane—it's a pure hydrocarbon refrigerant, and yes, it's highly flammable (A3 classification).

As for R-32 (difluoromethane), it's a different refrigerant altogether, but you're also right that it's flammable too, though not as much as R-290. R-32 is classified as A2L, which means:

• A = Low toxicity
• 2L = Mildly flammable

So yes, R-32 is flammable, just not to the same extreme level as R-290. That "2L" classification means it burns, but it's harder to ignite and burns slower than full-on A3 refrigerants like propane (R-290) or isobutane (R-600a). Both refrigerants are commonly used in modern cooling systems, including ductless mini split systems, due to their efficiency and lower environmental impact compared to older refrigerants like R-410A. When choosing ductless mini split systems, it’s worth noting that R-32 is often favored for its balance of efficiency and safety, while R-290 is less common in residential units due to its higher flammability. Always ensure proper installation and maintenance to mitigate any risks with these refrigerants.