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Community and Q&A

Cold climate heat pump

gozags | Posted in Green Products and Materials on

Anyone have any luck with the MrCool inverters? Something to replace a ducted gas furnace?

Cape cod style in Spokane, WA. Existing gas furnace <80% efficiency (I believe late 80’s). No AC. Around 1600 sq/ft with some improvements. Basement is R25, rigid insulation, new windows, etc. Current furnace ramps up, then cycles a lot. Single speed. Utility costs aren’t wild. Hydro electric and nat gas are cheap compared to some rates I have seen.

Did a Mr Cool minisplit with a neighbor in a 800sqft garage (remodeled into an art studio with some insulation, drywall, etc) and it worked great. Super easy and seems to work just fine year round.

Big one is getting some AC in the house to lower the temp a bit in the heat of summer. We drag out the window shakers and scrape up the old window ledges and do that whole thing every year, never look forward to it.

Alternatively looking at the VRV dual fuel setups from Daikin, but that excludes me doing it myself.

Putting in the MrCool doesn’t look too daunting. I have prepped a sleeve for the lines, added power, pad, etc some time ago during the basement remodel.

Big fear is running into 0/5 degree overnights (recently) and then getting hit with a huge electric bill, where the gas would have kept up otherwise.

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  1. Expert Member
    Dana Dorsett | | #1

    To right size it with a reasonable but not crazy oversize factor first one has to get a handle on the design heat load at the 99% outside design temp (which for Spokane is +1F- +13F, yes, I know it gets a lot colder than that sometimes:

    Since there is a heating history on this place, run a fuel-use based heat load calculation:

    SFAIK Mr.Cool doesn't have a ducted "hyper heating" vapor-injection scroll compressor unit (though they have some wall-coil type cold climate mini-splits) and without that technology even an inverter driven unit is likely to suffer capacity efficiency issues at temps below +10F. Daikin doesn't seem to either. A right sized Fujitsu ducted minisplit unit won't crap out at sub zero temps, nor will several Midea/Carrier ducted mini-splits with "hyper heating" compressors.

    There ARE ducted mini-split heat pumps that can handle this. But coming up with the load numbers is the all important first step.

  2. _Stephen_ | | #2

    Mitsubishi also has some ducted units designed as a drop in replacement for a traditional furnace.

  3. gozags | | #3

    Thank you both. I need to do the manual j/d (whatever I might be able to do as a homeowner).

    I have access to all the gas and electric consumption for at least 10 years.

    An intriguing aspect of the MrCool option is the diy, including the various line set lengths to optimize the distance the the indoor to outdoor units.

    Dana, it seems the unit I referenced may not be on par with the Mits hyper heat and others regarding cold performance.

    I am sort of envisioning a ducted system that ramps up and down smoothly on a set point from a thermostat. How a mini split might work (but I don’t have a layout for that)

  4. bfw577 | | #4

    The DIY series have terrible cold weather performance. It appears the quick connect system doesnt work with vapor injection compressors. They completly stop heating at 5 degrees. I attched a performance chart from Midea/Pioneer that cross references to the DIY model. If you search on them its widely reported they have terrible heating capabilities. They start loosing heating capacity at 48 degrees. My Midea hyper heat is rated 100% capacity at -13 as a comparison.

    Mr Cool units are rebadged Mideas. They are way overpriced compared to actually just buying the unit from Midea who makes majority of the off name brands.

    Do some research and you will see these units are actually quite simple to install. They are installed all over the world for dirt cheap compared to America. Costco and Walmart stock them on the shelves in Mexico for a couple hundred dollars. Going rate in Mexico is $50-100 to install one. They are cheap disposable appliances in most of the world. I self installed my $950 Midea Hyperheat unit. I could still buy 3 more for what a professionally installed Mitsubishi would have cost me. Worth the risk to me for the huge savings.

    I read that the quick connect system the DIY series uses is actually extremely reliable. The same system was widely deployed by the US military in Iraq and Afghanistan. A mini split could be installed quickly without dealing with any open refrigerant lines or vacuuming . Sand contamination was a big issue as well and this system completely eliminated it.

    You are in one of the best states to deploy a heat pump. WA has a pretty mild climate and the 2nd cheapest electricity in the US after Louisiana according to the EIA. You guys have a ton of cheap hydro. I would think it would probably be significantly cheaper compared to gas. The other huge benefit with a heat pump is they can be powered off solar panels. I have panels with net metering and heat my house with 2 12k mini splits. The combination is no doubt the cleanest and most efficient way to heat as you are using zero fossil fuels. Its really awesome to look at my electrical monitor seeing the mini splits being powered directly from the sun and sending the majority of the power back to the grid. I attached a snapshot from yesterday's data as an example.

    1. ohioandy | | #5

      BFW, can you clarify your experience with Midea. Are you saying there is a product line that's set up for DIY "plug and play" which has quite poor performance numbers but is reliable, and then there is the standard product line which requires skilled lineset work but has very good performance? I spent some time surfing the online stores and their documentation can be a little vague.

      1. bfw577 | | #6

        Pretty much. Mr Cool makes one unit that is DIY with the quick connect fittings. That unit is not a cold climate unit. It is reported to be reliable and gets decent reviews. A military hvac person commented on a hvac forum that has one. He said its the exact same setup and identical valves they used in Afghanistan. The quick connect fittings are supposedly made by a US company. Even Costco sells the Mr cool diy units pretty cheap for $1099 with good reviews. That same Midea unit that the Mr Coo diyl uses without the quick connect fittings is around $600-700 online. So your paying a premium for the quick connect fitting setup.

        Just remember though that these units would probably only work good heating in a place with a really mild climate. At 25 degrees the capacity is cut in half. So a 12k unit is only putting out 6k btus at 25 running full speed at poor efficiency. These would be terribly inefficient here in New England and a good chunk of the Northern US that experiences decent cold. If you just want one for cooling they are fine and have great performance.

        Midea is the worlds largest air conditioning and appliance manufacturer. They teamed up with Carrier here but have a tiny market share. Almost all these off brands Mr Cool, Senville, Pioneer etc are all made by Midea. My Midea floor console unit is identical to Daikin, Fujitsu, and other brands. It seems they are all probably coming from the same factory. Midea is gaining ground with the growing popularity of people doing diy installs. Their premier hyper heat series 12k unit can be had for $950 shipped to your house. Its close to half the price of big names like Mitsubishi with similar and often times better performance. Gree the 2nd largest Chinese manufacturer is currently producing the most efficient mini splits based on the AHRI data.

        1. lance_p | | #8

          Interesting... I wonder if Midea is the OEM for the Alize heat pumps bundled with Dettson Chinook furnaces? One of the many reasons the Dettson Chinook furnace is appealing is that it comes with a heat pump system instead of just an air conditioner. The downside to their heat pumps is they don't have great low temp performance; the 24KBtu unit only heats to about 20F and is down to 55% capacity at that temp.

          If Midea is the OEM I wonder if one of their Hyper outdoor units could be substituted for the standard Alize model? Here are links to the system and the tech info:

          I'd love to have a system that allowed electric heat most of the year, even if it meant relying on gas during really cold temps. I'm in Ottawa with a design temp of -13F, so a hyper heat pump is about the only thing that would work here.

          1. bfw577 | | #9

            Thats a rebadged Gree Terra. Here is thr Gree Terra service manual. Its identical to the dettson service manual you linked. You can also visually see they are identical.

            China is notorious for one or 2 big companies producing most of the same products with different brands slapped on them. I have a 50cc chinese scooter. They are all built in 2 huge factories by the same company then a dozen or so companies put some stickers on them and export them.


          2. lance_p | | #10

            Reply to BFW, post #9

            Excellent, thanks for the info!

            Funny, the heating performance chart looks very similar, but the Gree manual actually specifies reasonable low temp heating performance (70% capacity at 0F).

            I wonder if the info in the Dettson manual is incorrect? It wouldn't surprise me if it was since the performance is dismal for a heat pump, especially one marketed and sold to Canadians.

    2. Expert Member
      Dana Dorsett | | #18

      >"You are in one of the best states to deploy a heat pump. WA has a pretty mild climate and the 2nd cheapest electricity in the US after Louisiana according to the EIA. "

      Spokane is on the cool edge of US climate zone 5, not a super cold climate but hardly "mild".
      It's nowhere near as temperate as the western half of the state. It still calls for a cold-climate type compressor, not one of the Mr. Cool DIY types. I don't believe Mr. Cool has a DIY-ducted version either (not that I check their lineup very often.)

      But electricity IS pretty cheap there (relative to most of the US.)

      A right sized hyper-heating ducted modulating Midea or Fujitsu could be done as a "mostly DIY" installation for pretty cheap if you can find an AC contractor with the tools experience to properly pump down/purge the system and install the proper refrigerant charge.

  5. _jt | | #7

    I have one - but not a the quick connect version. AMA. After I pulled it 6 inches off the ground cold weather performance for NJ - 99% = 15 deg F has been great. Performance seems a little better than spec but more importantly:

    1) capacity has been fine in the teens - minimal defrost cycles.
    2) keeps my family room and kitchen about 10 degrees warmer than my previous hydronic system for a comparable if not slightly lowe price when it's in the tens.
    3) On warmer days, when in the 40s, it keeps the rest of the house warm as well for minimal cost.

    Overall I am happy with it - but that being said knowing what I know now I would get a slightly higher seer/hpsr unit midea knock off - like a senville, pioneer or blue ridge. They are all the same - but you can definitely get better performance for the same price as Mr Cool.

    For instance Pioneer has a 21 SEER, 12 HPSR unit for around 800 at Plus it has some subzero performance as well in case you need it.

  6. gozags | | #11

    Some good info everyone, thanks.

    Sounds like the quick connect DIY feature pushes some cold performance features off the table for this series.

    Jay, did you diy the install and then have someone do the line set portion?

    1. _jt | | #12

      Amazon installation services. They sent folks from New York (about 30 miles away). They were very professional and if you are in the area I can recommend the group directly.

      I suspect I could have done it myself but the price wasn't bad. And they came within a week and did the job with 3 people in half a day. They were originally from outside the US so they had a lot of experience with mini splits.

      Also - they did have to top off the pre-charged lines quite a bit so be warned they aren't always accurately filled. (Which is of course hard to tell if you DIY)

      Only problem was they kept the pump on the ground, so first freeze I had the "igloo effect" - but once I got it off the ground it's been running great.

      1. Expert Member
        NICK KEENAN | | #13

        So you bought the unit from Amazon and ordered the installation as well?

        That's something interesting to keep in mind. One of the issues I keep hearing with minisplits is finding someone local to install it.

        1. _jt | | #14

          Yes - logistically it was very helpful since we had a 100 degree heat wave and Prime got it to me in a couple days and the installation within a week.

          But if you have time, buy from highseer or another distributor online. (Each "brand" has it's own distributor, but they are all Midea's - they use the same apps, USB interfaces, connect to Alexa the same way, etc.)

          These things are effective. Temperatures were in the low 20's last night, so you can see ramp up from 65-75 deg F while outside temp was around 25 this morning. It used about 1.5 kw of power to do that.

  7. gozags | | #15

    Never thought of amazon. And your point about the precharge not being full was something I had thought about and something you wouldn’t know if you diy.

  8. ohioandy | | #16

    Wait, so you guys are talking about ordering a minisplit AND the installation AND the commissioning (lineset charging) on Amazon? Like, the website??? And that's a thing??

    I wonder how that would go in my neck of the woods (rural Ohio.) Last time I put in a minisplit, I bought a Fujitsu from a local HVAC shop so I would have the warranty. It was about 30% higher than the online price, but I figured the warranty was worth it. I did the entire installation, including running the lineset and doing ALL the electrical connections. Then their tech charged almost $600 to hook up the lineset and do the pressurizing. (He muttered the whole time about my terrible mistake of replacing an 80 kBtu furnace with a 12 kBtu minisplit, but that 's another story).

    I'm just really interested in hearing about alternatives!

  9. gozags | | #17

    This proclaims to not need supplemental down 0 degrees. If does have an optional heating element.

    I know 1:1 outdoor to indoor unit is preferred but this looks as if it could run the ducted portion with our existing system and, if we choose to add-on a small addition, we could add a ducted minisplit and feed 3 bed/1 bath on the second floor.

    We have two 6” runs from the furnace to the .5 second story (essentially two small bedrooms). Those runs would be pointed down through the ceiling on the first floor and the second indoor unit could run the second floor (with addition) exclusively. Seems like it might work.

    1. Expert Member
      Dana Dorsett | | #19

      The Daikin units are NOT cold climate versions, and will crap out on capacity pretty quickly below 0F. The knee in Daikin's capacity curve where the capacity begins to fall off more steeply seven on their better stuff happens north of +10F, whereas with a vapor injection cold climate type compressor it's still pretty good +5F, and will often have 75- 80% or more of it's "rated" capacity at -10F.

      Most of WA has pretty good distribution & support for Mitsubishi (at least west of the Cascades, where my relatives who heat with mini-splits live), not sure about Spokane. It's important to have at least some amount of local installer knowledge (distributor support is even better), and I's be surprised if Daikin has enough market share in eastern WA to have much in the way of support. Carrier sells re-labeled Midea units, and a Carrier support chain may be able to service a Midea, if it's a model that they re-label.

      But all of this is a bit silly to get into before the load numbers are better understood. Short of a Manual-J have you bothered to run a fuel-use based heat load calculation yet?

  10. twoodson | | #20

    What's the story on these? Seriously, they claim 100% heating capacity at -5F. 78% capacity at -22F.
    20 seer and 11hspf for the 2ton. It has a dip switch to set it to 3ton. It's an updraft drop in replacement for the 100 million houses out there with this setup. I was about to order another 2 ton fujitsu and I'm seriously considering doing this instead. How are they doing this?

    also, they seem to be better at marketing than everyone else I've seen.

    1. Expert Member
      Dana Dorsett | | #21

      >"What's the story on these? Seriously, they claim 100% heating capacity at -5F. 78% capacity at -22F.
      20 seer and 11hspf for the 2ton. It has a dip switch to set it to 3ton. It's an updraft drop in replacement for the 100 million houses out there with this setup. I was about to order another 2 ton fujitsu and I'm seriously considering doing this instead. How are they doing this?"

      Part of it is the definition of "capacity". They are referring to it's AHRI "rated" capacity, not it's maximum capacity at the AHRI test temperatures of 70F indoors, 17F and 47F outdoors.

      To get reasonable capacity at -22F they have to be using vapor injection type compressor techonology similar to Fujitsu & Mitsubishi, et al.

      One difference between a 2 ton Fujitsu and the 2 ton Mr. Cool Universal is that the Fujitsu modulates both air speed and compressor speed with load, whereas the Mr. Cool air handlers are single speed (comparable in some respects to Mitsubishi MVZ series air handlers.) I didn't find cfm or static pressure specs in the manual for the air handler. The same air handler is used for both the 2 ton and 3 ton compressor, with a DIP switch setting on the control board to the air handler to set it's parameters appropriately.

      1. gozags | | #22

        900 cfm on 2 Ton and 1000 on 3 Ton, per what I read online (for the Mr Cool).

        We have Carrier around here. Commercial and residential. Perhaps I can dig into the Midea units a bit. I need to redo my numbers though since we have fully insulated walls in the basement now.

        What I found though is that when I got some local quotes they basically all charged same $6-7k and the proposals were all the same - gas furnace, conventional AC compressor outside.

      2. Jon_R | | #23

        The 2 to 3 Ton MrCool Universal Air Handler is variable. Which is the only thing that makes sense for AC with a variable compressor.

        1. gozags | | #25

          I haven’t seen anything about an ECM motor in the handler for the Mr Cool solution. Some literature suggests that the units are ‘non communicating’ - so the outdoor unit doesn’t speak with the indoor at an advanced level?

        2. Jon_R | | #26

          Maybe "variable" only refers to the 2 vs 3 ton selection done at installation and then it is a single speed? It's poorly documented - needs to disclose modulation range on both parts.

          1. gozags | | #27

            So on this site here, they have more details and their is a video or two showing some pretty impressive cold weather performance.

            It implies variable output on the handler. So I guess there is variable compressor output, variable air handler CFM and then perhaps variable refrigerant flow? I suppose that is tied to the compressor modulation?

          2. lance_p | | #28

            In the -24F video the performance graph looks like it just cycles on and off at full power, it doesn't appear to modulate.

  11. bfw577 | | #24

    I think there was another post here recently where the person called Mr Cool and they confirmed it was made by Midea.

    The cold performance specs appear to be the same as the Midea Premier units and it probably has a Toshiba vapor injection compressor.

    I have a Midea Premier floor console and it came in a Midea Carrier North America box from Georgia. There were both Carrier and Midea Midea stickers in the box.

  12. gozags | | #29

    Lance - I noticed that, but I was taking those dips as when it went into defrost mode? They were dealing with colder weather than what we have here (Spokane, WA - cooling 96, heating 10).

    1. lance_p | | #30

      IIRC he made reference to a defrost event just before the unit turned on and stayed on for the night. My impression was the defrost event looked different than the pulses before that, but I’d have to watch again to be sure.

      If that video is an accurate depiction of its performance it certainly seems to work well. Having said that, we have no idea what the actual heat load of the house is or how efficiently the HP is performing.

      There’s a certain “marketing” feel to it... who cares if the registers are warm? It’s the house we’re concerned with. Definitely targeting the homeowner, not the HVAC professional.

  13. MR_COOL_Dealer | | #31

    Both the MRCOOL Universal Heat Pump and their Ducted Central Heat Pumps are DIY when using their no vac pre-charged linesets. A test was done a year are so in Wyoming with the mrcool universal heat pump using no auxiliary heat kit in -20 and managed to keep the house at 73. here are some examples

  14. walta100 | | #32

    MR-COOL-Dealer are the “no vac pre-charged linesets” really shipped with a vacuum inside the line set?
    Sure sounds like that when you open the service valve to the unit.


    1. Deleted | | #33


      1. aaron_p | | #34

        Walta - I understood these to already vacuumed and filled with R410A based on the line set length so there is no calculations needed for additional refrigerant. Would also be interested in long term durability of these to resist leaks. I can't imagine they are any worse compared to the average HVAC install but not really sure. The bigger downside I could see is if these aren't reusable at the unit end of life or change-out. I assume these quick connects are one time use?

        Also, interested in the cold weather performance and modulation abilities as the 2 ton should meet the needs and be a fairly simple swap for the current gas furnace/ac system in my climate. The documentation about the operation and modulation seems unclear based on this thread.

        1. aunsafe2015 | | #35

          Can't comment on long term reliability of the lineset.

          But these are supposedly rebadged Gree Flexx units. Air handler can only run at one speed, so dehumidification might not be the greatest. Modulation capability is 50% of max (2-ton unit can modulate operate between 12k and 24k btu). Cold weather performance is good. I think the docs say 2-ton unit is 100% capacity all the way down to 5 deg. F or so and still putting out a decent amount of heat well below 0 F.

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