The Walden Effect: Farming, simple living, permaculture, and invention.

When and how to DIY a minisplit

Minisplit install

We learned a huge amount during our recent minisplit install, and I thought I'd try to sum up the most salient points in one post to help others who might want to follow in our footsteps.

First --- is a minisplit a good idea in a trailer? Most installers told us no because the rooms at the far ends of the mobile home won't receive uniform heat. We're used to heating with a wood stove, though, and don't mind using space heaters at the extremities to top off heat as necessary. We figured the much higher efficiency of a minisplit compared to a mainstream electric furnace or traditional heat pump counteract this slight downside and we still feel that way after enjoying our new device for a few blissful days.

A slightly more tricky issue is the potential for water lines to freeze. I hadn't realized that trailers are designed with air-duct heating in mind, so the water lines run beside the air lines under the trailer. We'll keep you posted if this issue materializes and requires an outside-the-box fix.

Pressurization equipment

Next, let's look at the pros and cons of DIY versus the traditional route of paying to have a minisplit installed by a pro. After calling pretty much every HVAC company in the area, I've discovered that a minisplit like the one we got for $1,300 from Home Depot (plus about $200 in tools, $50 for the wall bracket, and $225 for the final line work from a pro) would have cost us $5,000 to $8,000 if we'd gone the traditional route. So, yes, we saved big bucks doing a lot of the work ourselves.

On the downside, we won't have the support of a licensed dealership behind us if anything goes wrong. And it's possible our machine won't be as long-lived as the Mitsubishi models several of the dealerships in the area are peddling. Once again, we'll cross that bridge when we come to it. For now, I'm pretty happy with getting such an efficient model on a shoestring budget.

Testing minisplit lines

Finally, when do I recommend calling in a pro? A reasonably handy DIYer should have no problem installing both exterior and interior units themselves. Running the lines between them is actually less tricky than I'd thought as long as you take extreme care with making bends gently and slowly.

And the connections (with pre-flared lines like the ones that came in our kit) are less finnicky than I'd thought. Mark and I went to great lengths to buy fancy torque wrenches and get the tightness just right...but our tech finished the job with ordinary wrenches by feel. Basically, you just want the connections to be tight.

So what's it worth paying for? Go ahead and call in an HVAC expert to test the lines with nitrogen, pressurize them, then release the refrigerant from inside the unit. First of all, it's illegal to do this step yourself. Second, this is the tricky part that most benefits from fancy equipment. For $200, a pro will do it right...assuming you can find someone in your area willing to work on equipment not their own.

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.

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Pipes probably won’t freeze if you use something with some r value to it for underpinning. Maybe even block with insulation dumped in the holes in the cinder block. Bales of straw if nothing else.
Comment by Anonymous Wed Dec 13 08:39:12 2017
Heat tape could be an easy and cheap way to remedy any pipe freezing if you have access to any of the pipes.
Comment by Brian Wed Dec 13 09:04:19 2017

I had a friend who lived in a mobile home and heated with wood, the only way he could prevent water lines from freezing was to run new lines inside on the ceiling, problem solved.

I plan to install a couple mini splits in our mobile home and treat rooms as individual zones.

The trend now is to treat crawl spaces like you would a living space, insulated, moisture barrier, and heated or cooled. My hot water tank heat pump is in the basement (which is a seperate zone) and is dehumidified by the heat pump.

Comment by zimmy Wed Dec 13 09:29:49 2017
I don't think you've closed in the bottom of your trailer yet, or if you have, do you have access to it underneath? If you have access, the first thing you should do is get the waterline insulation wrap at your local Lowes or Home Depot and wrap all those waterpipes! You'll be glad you did. I did that when I first moved in in 1999, and my water pipes from the well to the inside of the house sit on the ground. Never have had one problem with frozen pipes, unlike my neighbor who didn't do that and he has to put a heater under the trailer to keep the pipes from freezing. An ounce of prevention is worth a pound of cure. :)
Comment by Nayan Wed Dec 13 09:55:30 2017
It is against the law to discharge refrigerant to the atmosphere. It is also illegal to sell refrigerant to anyone who does not have an EPA 608 certificate. It is not illegal to use nitrogen under any circumstance and it is not illegal to charge any equipment you own. You can find any refrigerant you want on Craigslist or Ebay. You are not breaking any law by purchasing it, they are by selling it.
Comment by fifth_disciple Fri Dec 15 00:46:53 2017

Our experience with DIY or "I know a guy" is it can back fire. A few years back our conventional heat pump compressor defecated in it's sleeping place...

The husband of a co worker did HVAC, and did side work. I handed him money and helped install a new outside compressor/condensing unit.

Two weeks later it starts making noise, the reversing valve went bad. It wasn't too cold out (winter in south GA) and we had to wait until he could come fix it as he has a regular job.

That summer the new compressor failed in August. He was deployed on his two week summer National Guard hitch. We stuck a small window unit in the living room and all had to hang out there- it was near 90 in other rooms of the house.

He eventually got it fixed but he got hosed as not being a dealer for the unit they paid him NOTHING for his warranty labor, just supplied the part.

Next time I'll pay the price and get an outfit that can come 24/7 and deal with any issues!

Comment by Eric Wed Dec 20 06:29:03 2017

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