The Typical Refrigerant Leak

I envision a typical refrigerant-loss-over-time scenario as one in which refrigerant is lost through a slow leak (a one hour leak-down test at the time of installation will ‘pass’ a system that will slowly leak refrigerant, an overnight test is far more reliable but there are cost and temperature change issues that often keep that more robust test from being done at installation) and for a while, there is little to no impact on capacity. Then, when enough refrigerant leaks out that maximum capacity is significantly impaired, no one notices this until there is a low outdoor temperature event which the heat pump can no longer satisfy the setpoint due to the capacity impairment – then someone finally notices the heat pump ‘isn’t keeping up’.

Then maybe the owner takes action, or maybe it gets warmer outside and they ignore it for a while, or even over the summer it works fine for air conditioning when less capacity is needed, until finally in the next heating season during that first good cold snap it becomes obvious something is so wrong that the owner finally takes action.

Some HVAC service professionals may attempt to identify and repair the leak, but many can give the homeowner a choice: ‘have us try to find the leak for $XXX per hour and maybe we find and fix it after a few hours, maybe we don’t, or we can just add some refrigerant for much less money.’ Adding refrigerant (perhaps blindly taking a guess, perhaps attempting a test to quantify the amount of refrigerant needed, but that takes more time, and time is money) is the ‘fix’ I typically see. For residential scale systems there is no law stating you need to try to find and fix a leak, so many people will just live with the occasional service call, maybe it becomes part of annual maintenance to ’top off the refrigerant’ (like it is motor oil) during that visit. I had one case of a person who built a very high performance house (R40 walls, R5 glass, 1.5 ACH@50, etc.) who had her installer come back no fewer than 25 times to recharge her system before finally deciding to install new equipment.  I made a rough attempt to calculate the direct global warming impact of the refrigerant loss and came up with about 87 years of operation with a properly functioning system with a typical grid emissions factor

Meanwhile, during the phase of this leak / refrigerant recharge cycle in which capacity and COP are impaired but this is not acted on, more electricity is used due to lower performance, resulting in more greenhouse gases from electricity generation, and depending on the emissions factor of the electricity, this might be greater than the refrigerant emissions impact – I’ve not seen good data on this, but this slide gives me pause, see slide #9 in [this EPA presentation which suggests that the largest impact of leaks is through increased electricity use.]

I’d like to see more data on these impacts, but it may be that we are on average digging the hole deeper unless we can do better at refrigerant management. Maybe we need to address this ‘quick recharge fix’ loop somehow.

I wonder if the way MA is doing GHG accounting is unwittingly diverting attention from refrigerant leak impact. I’m thinking of the convention that MA is using for reducing GHG emissions from the Buildings Sector, e.g. if you are burning a fossil fuel to heat your home and you switch to 100% HP for heating, MA GHG accounting has that as a reduction in space heating GHG emissions to zero. The GHG emissions accounting shifts the electricity related emissions to the Electricity sector, probably for the sake of simplifying accounting. But is the emissions from HP refrigerant leakage accounted for in the Buildings Sector ? I’m not sure, but I don’t think it is, so maybe it is ‘out of sight, out of mind.’

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Published by Will Brownsberger

Will Brownsberger is State Senator from the Second Suffolk and Middlesex District.

9 replies on “The Typical Refrigerant Leak”

  1. I’m surprised that packaged Air to Water units aren’t more popular in New England given how many forced water heating systems there are here. These units use water as the heat transfer medium to move energy around the house instead of refrigerant. These units are factory sealed and tested and shouldn’t leak — in addition, since all the refrigerant remains outside, mildly flammable refrigerants with low GWP can be used safely.

    We’ve been looking into these systems at our house, but the costs we’ve gotten have been extravagantly high.

    1. Agreed. I think that air-to-water heat pumps using propane as a refrigerant are in the future. Propane is low global warming potential but flammable and cannot be circulated inside, but we can hope for design improvements that allow an external heat exchange to water. They need to become hotter than they are today; today’s units don’t warm the warm water enough to use in typical radiators.

  2. Interesting. But I’m not clear what the expert feels is the most cost-effective approach. He seems to be saying that topping off and a search for the leak may be problematic. Which is the best of the not-so-great options, and at roughly what cost?

    1. The expert is making the point that leaks make heat pumps less cost-effective. There is no immediate solution on this. Heat pumps are less cost-effective than we would like them to be when we analyze all factors objectively. We can expect technology improvements over the next few years. For more see generally the posts under the “Heat pump analytic issues” in my heat pump outline.

  3. Just by living, it is pretty hard to not have an impact on greenhouse emissions (what we eat, where our waste goes, how we heat and cool, how we get around, etc). It seems everything we do has caveats that make that thing less efficient or actually just as destructive. What bothers me is how people jump on the latest “solution” as the end-all-be-all. Heat pumps are one of those solutions that always left me asking questions: will it work in cold? how expensive is it to install? can I even install it in my old house? does this installer know what they are doing? what else will I have to do to even be able to install (increase the amperage into my home $$$? remove old knob and tube so I can insulate $$? do I keep the gas as backup?)

    I appreciate you writing about real-life info on your personal installation of heat pumps. I can’t say I’m too enthusiastic. I have friends who have installed them in newer houses. AC is good; heat is dry and just OK; getting a good installer is a crap shot. The refrigerant issue really bothers me and how it is being ignored is not good. If winters keep getting warmer like they have been, I’m not sure a retrofit is worth it over just conserving as much as you can.

  4. I installed heat pumps this past July. Wonderful to have AC for the first time in our house. Heating was OK but not as good as our natural gas radiators. We’re having our installers, OBIE HVAC, return for a free annual maintenance this May. We’ll see what they find.

    I am still happy we installed these heat pumps. Is it a perfect end-all-be-all? Absolutely not. Does it move the technology further towards sustainable solutions for our planet? Yes. Solve one problem and you discover others. Innovation is 2 steps forward, one step back. It’s hard work and not for the easily discouraged but I’m glad to be part of the process of moving technologies forward to create a sustainable future.

    All that said, do we need better laws here to incentivize preventing leaks in the first place and when they do occur, tracking them down and repairing them? Right now installers and customers seem incentivized to just put in more coolant.

    Finally, Senator, you say, “Homeowners should be checking the temperature of the air blowing out of their heat pump air handlers indoors — should be over 100F when heating!” Can you provide some more details and perhaps a link to a diagram? What exactly are “air handlers?” I have an oral thermometer to check if I have a fever. Does that thermometer work for this or do I need a specialized one.

    Thanks for all of your attention and work here, Senator, and for everything you do!

    1. The units are mounted about 6 feet off the floor on the wall (for air source heat pumps, which is what most of them are). Warm air blows out the bottom louvers; they are usually white. Any ‘normal’ thermometer (not one for measuring for a fever) will do, and anything over 100 degrees F is considered acceptable. Just hold the thermometer in the air stream.

    2. Darrell’s answer is good. Just to add to it: In a ducted system, test air at a hot air vent that is close to the air handler. The air handler is the fan that moves air inside the ducts.

      EPA is on this case and is forcing change in the kinds of refrigerants we use. Their changes will not be fully effective until January 1, 2026. I personally wouldn’t encourage a friend to buy a heat pump using the current generation of refrigerants unless they expect to use their heat pumps very heavily; heavier use means more fossil fuel displacement to offset the negative environmental impact of all-too-probable leaks.

  5. My daughter has to make some decisions about various systems in her house. She is considering heat pumps, and I forwarded your recent analysis to her. One other thing: when we installed our whole-home heat pump system (hybrid of mini-splits and ducted), we were able to get the full MassSave rebate by certifying that it we would only use the old forced hot water system as backup (a commitment we’ve been able to fully honor — heat pumps kept up with cold over past 2 winters) — but now MassSave appears to be requiring complete disconnection of the old system, so no backup is the heat pumps fail or electricity is out for a long time.

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