Replacing a minisplit heat pump inside the main house and installing a ceiling cassette minisplit, both from Mitsubishi, in the backyard stylish shed. Even if you don't install a minisplit yourself, it is good to understand the work involved so you can plan and build your house accordingly.
TRANSCRIPT
Last time, on Building Resilience, we put Variform siding on the wall.
And panel and channel cladding...
And open joint cladding...
This time, we’re going to talk about mini-split heat pumps…
All minisplits are heat pumps, but not all heat pumps are minisplits
Michale Anschel: When we talk about heat pumps, we aren't always talking about mini splits. But when we talk about mini splits, we are always talking about heat pumps.
Mini-splits are like room-sized heating and cooling systems that can extract heat energy from the air.
Traditional heat pumps are less efficient as temperatures drop into the 40s and 30s, so heat pump adoption in the north has not been the smoothest of roads…
MA: Heat pump adoption up here in the north has not been the smoothest of roads. In fact, 20 years ago, we weren't allowed to use them as a primary heat source.
And frankly, the technology just wasn't there yet, but a lot has changed since then. And now they are an option worth considering, especially with things like hyperheat for Mitsubishi, which can comfortably perform down to minus 20 degrees. And when it's not freezing cold out, boasts a pretty impressive efficiency of 4.68 COP, which is like saying 468 percent efficient. And when it does get down to zero or minus five or minus 20, that might drop down to say. 1. 6, 1, which is like saying 100 percent or even maybe as low as 70%.
But you compare that against a traditional furnace or boiler that's running 96, 97 percent efficiency at its peak performance. And that's still a pretty good deal.
And that’s why we are replacing this old unit with a newer, more efficient one.
This fifteen-year-old unit is much less efficient than the new minisplits.
Minisplits can hide in the ceiling
And when we talk about minisplits for most folks, what they envision in their largely views as obstacles are unattractive. Um, but there are a couple of heat pump mini splits. on the market now like this one from Mitsubishi that do a great job of concealing themselves so that you don't even know that they're there.
This is a ceiling cassette so this one nests nicely up into the ceiling and the only thing that will be visible when it's done is a nice white grill in this case which will blend in with the drywall.
Where do we put these things? We generally locate them on or near exterior walls because the exterior wall is the one that's subject to the most temperature change from outside.And we want to use the warm air to wash across the glass to help minimize condensation. The nice thing about these units being supplied on the ceiling or high on the wall is that that air moves across the room and gives a good, balanced wash to the entire space.
Now the condenser unit, where do we locate that?
That’s easy. You put it outside the house. Duh.
My favorite place, uh, and way to install the condenser is to use the wall mounting brackets so that I can mount it to the side of the house.
It's well off the ground, three or four feet off the ground.
There's good air flow all the way around the unit, and any snow accumulation and then also the ice that comes off the unit is not going to be anywhere near the unit.These things produce a lot of water when you run them in the winter, and that water quickly becomes ice. And we want to make sure that, you know, we're going to have a four to six inch thick sheet of ice that's going to build up wherever the drain is, and we want to think about where we want that ice to be.
So we are putting this condenser unit outside, toward the back, where nobody will be walking in the winter, and off the ground in case there is ever any snow in Minneapolis.
The indoor unit and the outdoor units are connected with four lifelines: two refrigerant lines, a condensation line, and an electrical cable.
You can attach the electrical line to the indoor unit before or after mounting it to the wall. Either way, mounting it to the wall involves precisely locating the mounting bracket and a three-inch hole in the wall.
Another innovation that we saw from Mitsubishi with these ceiling cassettes has to do with how the line set connects to the unit. Now, typically, when a mini split is going to have a failure, it's where the line set meets the ceiling cassette, and you have to chip out a bunch of drywall to get to it.
But what they did is they made their cover a little bit larger. So you can see that instead of the cover ending here, this is our drywall template. It comes all the way out to about where these wooden blocks are. And that means that If there's an issue with the unit and they have to service it, you can pop the cover off and access the line set without doing any damage.
Installing a wall-mount minisplit
Let’s go inside to see how the wall unit is shaping up. With the bracket mounted, Aaron pokes the refrigerant, and the condensation line stubs through the hole in the wall. He feeds the electric cable through the box and sets the minisplit head into the bracket.
The air filters are fitted with air cleaning pads to remove allergens. The front panel is clipped into place closed, and the plastic is peeled off. Outside, we've still got those four lifelines. He will connect the condensate line first with a coupling and a hose clamp. At the bottom, it feeds into a line that runs into the perimeter drain.
To make the refrigerant line connections, he breaks out the flaring tool. The lines are attached with compression fittings and tightened with a torque wrench. With everything connected to the indoor unit, he coaxes the lines into the plastic conduit track and fastens it together with zip ties.
Install outdoor compressor above the ground
Now, they get the outdoor unit ready. Craig is removing the compression fittings to flare onto the refrigerant tubing while Aaron double-checks that the compressor will fit on the stand he just set up.
In theory, the numbers check out.
And they check out in reality, too.
The compressor is bolted to the stand, and they attach the other end of the lines. First, he cuts the tubes to the correct length and then flares the ends. Spreading refrigeration oil on the tubing end helps make a tight seal. Again, the compression fitting is torqued tight, and they test the system for leaks.
The system is pressured to 600psi with nitrogen for 24 hours to ensure no leaks. Then, a vacuum pump evacuates the lines and removes any moisture before refrigerant is released into the system. After charging the system with refrigerant, they cover the lines for a tidy installation and test the on/off button.
With everything working fine, they put the cover panel in place and head home.
Next time we’re going to jump back up on the roof to lay down some standing seam metal roofing from ABC. We’ll clip it in, screw it down, and fit the parts together like the pros do.
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