How to Connect the Line Set to the Outdoor Unit and Vacuum Test It

So right now, for example, we are not mounting this on the wall — it's just on the floor here — but we're going to connect the line set from this indoor unit to this outdoor unit here. Normally with this indoor unit, it should be a little bit above head level, so I'd say two and a half meters. This is lower than it normally would be.

Does it matter that much? Well, if it's at this height — a low height — you're going to be broadcasting a lot of your supply air more toward the ground instead of toward the users, so you won't have the option to have the air spray toward the users. So the higher the better, but it can't be right at the ceiling. Why? Because the return air comes through the top, and that cycles through the coil to get cooled again. There should be around five inches — check your user manual — but there should be about five inches on either side of the unit, and then five inches above it, and then about 90 inches or so from the ground.

So imagine that indoor unit being mounted up here. This line set here — remember, we made it nice and straight — goes through the wall off to the left or off to the right behind the indoor unit, and now it's going to be brought down straight against the wall, downward, to this outdoor unit here.

All right, so the next step is we're going to connect the line set the same way we did on the indoor unit. The flared fittings are similar — these are male flare fittings right here, and we're going to have female flare fittings on this line set. There are female flare fittings on either side of the line set.

So the top one, the 3/8-inch one — we'll start with that one. Again, same as we did on the indoor unit: make sure everything is nice and tight and well connected. Tighten by hand until you can't tighten anymore by hand. Notice that there isn't another nut on here, so you only need one vice grip or adjustable wrench to do this. We're going to do about a quarter turn — actually less than a quarter turn. You'll feel it get to a point where it strains; that's when it's tight enough. Don't tighten anymore, because bad things will happen.

Do the same thing with the quarter-inch fitting. Again, an important part of this is that if it's not threading well, stop, back it off, and start again. It needs to thread well by hand before you bring out any wrenches.

Okay, now take off this protective cap here — usually it's just hand tight; you might need a wrench, but in this case it's hand tight. This is the low-pressure line, the 3/8-inch one, and that's where the port is where we're going to do a pressure test to see if we actually have a closed loop here. If there are leaks, that's a problem.

So it's smart to use a tank like this one and a port like this, and attach it. Then we're going to release the nitrogen and see if these gauges maintain the pressure we set at the beginning.

Okay, so Todd's turning it to 300 PSI. We're just going to let it sit like that for a minute. How long, Todd? Fifteen seconds. Fifteen seconds.

You would hear it — you would also hear it — but you'll see in this gauge here, it looks pretty good, right? It's maintaining. Yeah, it moved, but it's maintaining everything, so that's a good sign. With that, we know we're not going to have the refrigerant leak. A little noisy, but remember, this is high pressure here, folks — this R-410A operates at like 500 PSI, so keep that in mind when you're working on this stuff. All that noise was the nitrogen leaving the system.

So now we remove this port as well, and now we're going to add the refrigerant.

Before we add the refrigerant, we actually need to vacuum everything to get the moisture, dirt, and anything else that's in this line set out of there, because if you don't get that out, bad things are going to happen — the refrigerant's going to get contaminated, and it's going to do bad things to the compressor. So you've got to do it, folks.

This set of gauges came with this adapter — a good set of gauges will come with this adapter — and that takes the hose down to the 3/8-inch male flare fitting. Again, make sure everything's lined up nice and straight; this whole thing just needs to be hand tightened. And here I am cross-threading it — so that's an issue. Ah, finally, okay, this is hand tightened.

This is a standard vacuum pump you can get on Amazon — maybe these days, with inflation, it costs a bit more. Turn it on and you'll see this gauge here: we're starting at zero, but it's going to start getting negative. How far do we take it down, Todd? 29.9 — as far as it will go, all the way to the end.

Close the valve; you should see the gauge stay there at 29.9. All right, so the vacuum's off — is it staying negative? It should, as long as we have a good closed loop without any leaks. Yeah, it's holding at 29.9. Okay, and then just take this off quickly.

All right, so from the last step, this cap was off — we're going to keep it off, because we're going to check the operating pressure once we release the refrigerant.

Okay, these will probably require a wrench — you're going to take these caps off, because you need a 3/16-inch Allen wrench to release the refrigerant.

Okay, all right, so now it's show time. Lefty loosey, righty tighty — maybe you can hear that, but yes, there is flow of refrigerant happening. Take it to the end, and then back one — no, just — okay, working, and stop.

All right, so the refrigerant can now flow when the unit is running. Do put these caps back on and tighten an eighth of a turn. Okay, an eighth of a turn — again, so they're not going anywhere.