DIY Heat Pumps - The Thrill of Victory

A reluctant DIY installation

“I can’t fix it.”

He didn’t say it, but that’s what he meant.  He was the the fourth repairman who tried to fix our 88,000 BTU furnace at our two bedroom cabin near South Lake Tahoe.  The furnace was 3x bigger than it needed to be, couldn’t get enough air to cool itself adequately, and burned $400 of propane a month trying.  It never should have been installed, which made it even harder to trust the professionals trying to fix it.  Then, at the beginning of winter, it quit.  Great.  

So, with the days getting colder, I found myself with a choice - pay the $16,000 to have a professional install a heat pump or do it myself for, hopefully, a fraction of that.   

Vanquishing the Enemy

In the end, I spent $5,000 on the equipment, the electrician, and miscellaneous supplies - plus 3.5 days of my time.  I feel like I got a bargain next to the $16k and $26k professional quotes.  None of the professional quotes came with the critical blower door test and sizing recommendations I commissioned.  I’m not going to be an HVAC professional, but it didn’t take long to understand the language and know that the guy telling me a heat pump wouldn’t work below 30F hadn’t done as much research.  

I installed a Mr. Cool Universal (Ducted) 2-3 Ton heat pump purchased on Amazon.  There were a few deciding factors: 

1. EVERY reviewer on Amazon who received an undamaged unit had a successful installation.  All seemed to be competent DIYers who don’t know HVAC, but who have strong FOIH (figure-it-out-how).  Mr. Money Mustache’s installation was particularly helpful.  

2. Most said Mr. Cool support was helpful.  I found their support to be fantastic.  I immediately got someone on the phone and she helped me debug the thermostat until it was working.

3. The linesets come pressurized with refrigerant, which means you don’t need a technician to pressurize the system with refrigerant after installation, nor do you need to flare copper lines. This is a huge innovation.

4. The fact that, despite claiming to be manufactured in Kentucky, the units seem to be rebadged Gree’s, which are available and supported worldwide.  

5. I noted this before, but the howls of HVAC professionals about Mr. Cool and DIY installations in general seem disproportionate to the complexity.  I was bullied and ridiculed by the professionals for asking questions in forums purportedly about home electrification.  By the same folks who told me that the heat pump wouldn’t heat the house (math says otherwise), that it wouldn’t work in the climate (specs say otherwise) and that I’d never get it working (I did).  Lots of people said I couldn’t build an airplane too - I find those comments pretty motivating.  

The first day was spent figuring out how to dismantle the existing system and build a wooden plenum to integrate the heat pump with the existing return air ductwork.  Yes, wooden plenums are unusual, but I have the tools to work with wood, the plenum only handles room temperature air and wood has a higher insulation value than sheet metal.  It took us about half a day to get the old furnace out and about a day to get the plenum sized correctly (had to make it shorter twice). 

Day two involved running the pre-charged lines between the outdoor compressor and the indoor air handler. This was tough. The lines bend but, if you kink them, all the gas escapes.  I hired someone to help me run around under the house and get them routed.  Once they are connected and tight, then you release another valve to run the refrigerant from the line through the unit.  Hearing the gas flow into the unit was pretty thrilling.  

The final day was dedicated to electrical work, including hiring an electrician to run a new 220 line to the inside air handler (lots of power in case we want to add resistant heat as backup), connecting the compressor to the existing external wiring and connecting the thermostat.  The thermostat was particularly confusing with competing diagrams from Mr. Cool, Ecobee online and Ecobee technical support. Though I was crushed when it didn’t work immediately, I called Mr. Cool and got the supremely helpful Kelly on the phone.  37 minutes later, after checking each hookup and a few critical changes, it was blowing hot air.  Hugs all around. I hugged and high-fived everyone in the neighborhood.   

I’m not sure yet what the energy cost savings will be, but heating the cabin with propane was costing $300-450 per month, so anything less than that is a win.

Doesn’t look like much, but that is victory!  

The Bigger Picture

This project was not just about installing a heat pump; it was a deep dive into the realities and challenges of residential electrification.  My biggest takeaway: it shouldn’t be this hard.  

It was really hard to work with HVAC professionals.  Every installer in the area tried to talk me out of it and then sent what seemed to be wildly inflated estimates that 1) didn’t account for existing ductwork and 2) didn’t even reference crucial information about the building envelope and the heating needs.  This seems to point to education needed and also policy that might encourage professionals to advocate for heat pumps.

The arrangement with installers is binary - either they install or you install with nothing in between.  In the same way I paid for a professional electrician to hook it up, I would happily pay for a consult on the placement, the ductwork, the power hookups, routing the linesets and a host of other issues that would have cut the installation time in half.  

Support will be an issue when something goes wrong. Despite being rebadged mainstream units, Mr. Cool’s are disparaged by HVAC professionals.  Maybe it’s not about the units and more about cleaning up after DIY installations, but messy installations could be solved by more flexible working arrangements.  I’ll share more about this after the first service call.  This seems a reasonable risk for an $11,000 savings.  

Overall, like many projects, this was fun to finish (type two fun, right?) and I’m thrilled with the outcome.  But we sure have a lot to do to reach millions of houses.