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Hydrocarbon refrigerants, are they good or bad?

lance_p | Posted in Green Products and Materials on

So my wife’s car needs an AC repair and I got looking into refrigerants.  Based on what I’ve read, it seems most cars use R134a as a refrigerant.  Many companies sell R12a refrigerant, a hydrocarbon-based product, that they claim is much better for the environment than R134a.  Not only do they claim it is less harmful to the environment, but they also claim it uses less energy for a given amount of cooling as the required pressure difference from high to low side is less.

An R22a product is also available as a replacement for older residential/commercial R22 based cooling systems, and similar claims are made.

Does anyone have any factual and/or experience-based input on these hydrocarbon refrigerants?  How does R410a compare both efficiency and environmentally?

From what I can gather they start life as something resembling conventional propane gas, but are then treated and purified for use as a refrigerant.  They are apparently non-ozone depleting and have very low Global Warming Potential, and are used around the world.

According to the manufacturers, the main reason they are not widely used in North America is fear of flammability, which is apparently an unfounded risk as all refrigerants become flammable when mixed with lubricants under high pressure.

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  1. Expert Member
    Dana Dorsett | | #1

    R290 (nearly pure propane) has been the preferred replacement refrigerant for R22 (and some R410A systems) on bigger systems, with very comparable efficiency when charged and adjusted correctly for the change in refrigerant.

    Most other hydrocarbon refrigerants are mixtures of isobutane, butane and propane, and have only recently been approved by the US EPA for use in home appliances, but are already taking most of the market share in the Kigali Amendment signatory countries in Asia and Europe. R22A and R12A are mixtures formulated as drop in retrofits (no equipment adjustment needed) for R22, and R12 & R134A systems.

    Hydrocarbon refrigerants are are all much easier/cheaper to make than HFO refrigerants, and have very low environmental impact compared to HFCs, but have the subtle drawback of being highly flammable, which is why the EPA limits it to no more than 150 grams when used in home refrigerators & window AC, etc.

    >"...all refrigerants become flammable when mixed with lubricants under high pressure."


    R22 is not flammable, end of story full stop.

    R410A is not flammable when vented to the atmosphere, not even systems under high pressure or when mixed with lubricants. The only way to light R410A off is when MIXED WITH AIR AT HIGH PRESSURE, and with an extremely high temperature ignition source. That is a set of conditions that will literally never happen in your heating/cooling heat pump system. If it leaks it's at atmospheric pressure, and for all intents and purposes chemically inert (kinda, sorta) and will not support flame even at the leak point.

    HFO1234yf (and -ze) refrigerants used in some automotive AC systems are somewhat flammable at atmospheric pressure, but not nearly as volatile as butane, isobutane or propane.

    Refrigerants such as R12B1 & R13B1 banned for other uses under the Montreal Protocol are still used on aircraft as fire EXTINGUISHING agents.

    R744 used in some automotive AC systems is pure CO2, not flammable at all.

  2. Expert Member
    BILL WICHERS | | #2

    I’m going to only add a little bit to Dana’s very informative reply.

    Some of the blended replacement refrigerants can be an issue for future recharges since the different components vent out at different rates. That means you have to evacuate the system and recharge with virgin refrigerant, you just can’t top off with more of the same if you’re low. Some of the replacement refrigerants also have compatibility problems with the lubricants which require the oil to be replaced. Some of those oils have compatibility issues with the insulating (electrical insulators, not thermal) materials used in the compressor windings which can be a problem. We lost a rather expensive 10ton Carlisle compressor at work trying this as an experiment to replace R22.

    Other refrigerants like R123 are very efficient. I spec R123 for large datacenter chillers since it results in the lowest energy costs for the facility. R123 is slightly toxic (the mechanical contractors like to call it “three ball” ...), but very very minor. It is not flammable though, and mostly just sits in a puddle if spilled.

    Ice rinks usually use ammonia as a refrigerant. It’s very efficient, but it is extremely toxic and will kill you if you vent it in an enclosed space. Facilities using ammonia are required to have sensors and exhaust systems in case of a leak.

    All refrigerants involve trade offs. I’m told that regular old barbecue grade propane is a pretty good replacement for R12, but it can be exciting if you have a car wreck so it’s not recommended to try using it.


    1. Expert Member
      Dana Dorsett | | #3

      >"I’m told that regular old barbecue grade propane is a pretty good replacement for R12, but it can be exciting if you have a car wreck so it’s not recommended to try using it."

      Fuel grade propane has a range of contaminants, (some hydrocarbon, some other), some of which can't be all that good for the compressors, even if its sorta-right, and it doesn't come pre-mixed with compatible lubricants. Sounds like great hillbilly hackery for a car you're planning to get rid of and need to demonstrate the AC is "working".

      In a car wreck it's the spilled GASOLINE, (or battery if you're driving an EV) not the air conditioner that's going to be the bigger hazard. Most cars would take at most pound or two of propane in the entire AC system, most located on the other side of the firewall, compared to 6lbs+ per gallon for the stuff in the car's fuel tank. There is potentially about much gasoline under the hood as there would be of propane. The evaporator coil on the cabin side of the firewall is fairly well protected by the crumple zone.

      But there's a reason why HFO1234yf made it onto the EPA's "acceptable" list for use in automotive AC, and R290, R22A, & R12A did not. There is at least a reasonable theoretical possibility of a propane leak inside the cabin in the event of a car wreck, potentially enough to be a real problem.

      The newly raised limit to 150 grams for hydrocarbon refrigerants in home appliances isn't going to run the central air, but it'll run a decent sized refrigerator or dehumidifier. It's enough fuel to cause a real fire in a worst case scenario, but isn't likely to blow the house to pieces with a slow leak.

      By comparison the amount of propane potentially filling your basement with a 4 ton air conditioner leaking indoors could get REALLY exciting when somebody turns on the basement light switch to go see why the AC isn't working... Propane is heavier than air and tends to pool and hang at the lower levels of the house if it's leaking, which is why indoor LPG tanks aren't generally allowed. (What could go wrong? Ask Murphy!)

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