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How to future proof are refrigerant Lines?

rhl_ | Posted in Mechanicals on

Suppose you install today’s say Mitsubishi multisplit systems. If someone comes out with a newer say CO2 based system, how future proof is your install? Sure you probably need new indoor and outdoor units. How about the lines themselves? Any reason they won’t just work?

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  1. Expert Member


    I don't know enough to answer your specific question, but I think good one to ask about any part of a building is what its projected lifespan is in relation to the entire structure, and how easily it can be replaced. Locating services, or detailing things like windows, so their replacement minimized disruption is surely always a good idea.

    It can also play into the basic construction choices of the building form. A house with a crawlspace and trussed-attic lends itself to renovation or replacement, making it more future-proof that many other options.

  2. user-1112693606 | | #2

    Interesting question. Unfortunately soft copper tubing and fittings are not able to tolerate the pressure a CO2 system requires, potentially over 1000 psi.

    1. rhl_ | | #3

      can the lines be repurposed to run water? Then I guess the co2 could go to a buffer tank or something.

      1. Expert Member
        BILL WICHERS | | #4

        Chances are the refrigeration tubing will be too small to handle a high enough volume of water to accomplish much if you’re trying to do space conditioning with it. You’d need much larger tubing for that.

        The smaller diameters of copper tubing actually CAN handle CO2 pressures (see, but you’d likely need all brazed connections. I don’t think we’re likely to see CO2 used for a space conditioning system though. Ammonia maybe, but it has severe toxicity issues. Chances are we’ll just see new refrigerants used, and so far all of them have been fine with the same copper tubing that’s been used for refrigeration systems for decades. The switch from R22 to R410A increased line pressures dramatically, but still well within the safe operating limits for copper tubing so line sets could usually be reused.

        If you want a future proof system, run the line set through sleeves (short sections or conduit or pipe) through walls. This way if you need to replace the line set, at least the passages through walls can be reused.


  3. JC72 | | #5

    IMO it's not worth considering because if CO2 ever became standard you can bet that the size of the pipe is likely to differ.

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