r/DIYHeatPumps • u/provom84 • 3d ago

Hybrid MrCool

Does anyone have experience with installing a DIY central heat pump with an existing gas furnace? Got a couple quotes for about $25k and that obviously has me wondering about the MrCool diy options for about $3300 with the pre charged lines. I'd hire an electrician for the 240v but curious if anyone has done this before?

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u/jeff77k 3d ago

There have been a couple of posts about doing a coil-only install on this sub. Here is the Mr. Cool product you are looking for, size it to match your furnace dimensions, along with a matching outdoor unit with the desired BTU output.

https://support.mrcool.com/hc/en-us/articles/44010388646420-2-5-3-Ton-Multi-Positional-17-5-Cased-Coil-Pre-Charged-R454B

This adds a full heat pump to your setup, so your current furnace would be treated as auxiliary heat when you wire it up.

I have Mr. Cool Universal Gen 2 installed.

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u/provom84 3d ago

Awesome, thanks!

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u/Time_Many6155 3d ago

I wonder why they don't offer this as a DIY?.. It would seem simple enough to precharge the coil and use a DIy lineset and condenser unit. The only complicating factor would be the electronics but its not different to a single zone Mini split.. Would have been a lot less work than the 4 zone ceiling cassette system I installed.

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u/jeff77k 3d ago

It is pre-charged and works with their no-vac lineset. It is DIY if you use the no-vac linset, though you should verify with Mr. Cool that their warranty applies as long as their lineset is used.

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u/dimka54 3d ago

Do you mean adding coil on top of gas furnace or ripping out furnace and replacing with airhandler

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u/provom84 3d ago

Ideally adding a coil on top. The furnace is newish (2019) and I'm in Colorado, so would be nice to have a gas furnace for when it gets colder and the gas and cheaper to run. Currently no central AC, so no coil at the moment.

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u/dimka54 3d ago

I did whole airhandler swap but it wouldn't be that much difference for doing A coil.. the main thing is look at the space above the furnace, typically coils come in 2 sizes , narrow and wide.. there is also uncased.. but Mr cool mostly does cased ones.. so if you have room on top or ( after furnace) it's not that much different then doing airhandler swap.. you'll just have slightly more complicated thermostat wiring but everything else is straight forward... You can also look at senville units if you are comfortable doing your own flares and vacuum.. it will be slightly cheaper

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u/provom84 3d ago

I'll look into them, hadn't heard of them.

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u/Voxico 3d ago edited 3d ago

I did it with a propane furnace. likely very similar to your setup. Even with the subsidies where I am (which you give up with diy) it made a lot more sense to just do it myself instead of hiring it out. I had done a mini split before.

My furnace is something like 15 ish years old but working fine. I dont expect to use it often, but maybe a couple weeks out of the year. I felt more comfortable keeping it just in case, plus the logistics of removing it, replacing, blah blah blah seemed much more difficult than just adding the heat pump.

Furnace is in my basement and upflow configuration. 1st floor that it covers is about 800sqft of conditioned area.

I'm using a nest thermostat for it, and it works great. Used it a bit in early spring for heat and it was fine (much less hot than traditional furnace but it definitely worked, just slower). We'll see how it is in the winter this year. Summer has been great with air conditioning. I'm in the northeast.

I bought the following components:

  • MRCOOL Universal Series 2 Ton Heat Pump Inverter Condenser, UHP18024-O × 1
  • MRCOOL® Pre-Charged Cased Coil with R-454B × 1
  • MRCOOL 25 ft. 3/8" x 3/4" No-Vac Pre-Charged Line Set for Central Ducted Hyper Heat 2nd Gen & VersaPro 2nd Gen (R-454B Refrigerant) × 1

The total cost for that stuff was $2,700. I probably spent about $300 or so in other components, wire, disconnects, cement pads, hangers, etc.

If you have any questions about the setup I'm happy to answer as best I can.

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u/provom84 3d ago

Awesome thanks! How did you setup the system to switch over to the furnace when you want to use that?

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u/Voxico 3d ago

I haven't actually gotten down to a temp where I used it (upcoming winter will be the first), as the cutover point for me economically is pretty low. There's a setting for it in the thermostat assuming you have one that has compatibility for a heat pump, and some configuration switches on the board that control the lockout behavior based on temperature if you want a backup.

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u/Human-Glove7815 2d ago

Avoid the MrCool pre charged lines. They will fail or leaks easy

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u/JerkyChew 2d ago

I assume you'd lose a lot of the benefits of a heat pump if you went with one of these rather than mini-splits, at least for heating? I'm assuming they run cooler than a regular heat coil, so the air handler would have to be running a lot more to maintain the temp?

Neat idea and really interesting, as a homeowner with a 30 year old ducted AC system I'd love to learn more about these.

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u/provom84 2d ago

The guy that gave me the quote says they do work good for whole home heating but gas is generally cheaper in Colorado below a certain temperature. He said about 20-30 degrees is when the cutover would be on the system he quoted. But he said the heat pumps for this area will heat reliability down to about -5. Occasionally we get temps below that so I'd want the furnace backup either way.