Archive for July, 2010

Installing an AmVent AX12 “mini split” ductless room air conditioner

Monday, July 26th, 2010

I just succeeded in installing a one-room “mini split” A/C. I’d seen systems like this at high end B&Bs we’ve stayed at, and I found this one on Amazon, and since I needed the 25′ hose kit I ordered it from the distributor.

It came as three large boxes – the outside unit, the inside unit, and the hoses. I opened the boxes and took off the plastic and let everything sit in the garage a few days to outgas – the plastic really stinks. After a while the smell wore off.

I put the outside unit on a couple of 12″x12″ pavers from Home Depot, with about 6″ of gravel as a bed. One of the plastic covers (for the plumbing) was damaged, but it still works well enough that I’m not worried.

I mounted the mounting bracket for the inside unit high on the wall of the second story room we need cooled – it was a little tricky to get the screws (I used sheetrock screws) into studs and still use the holes in the bracket. It’s supposed to be accurately level so the condensation from the coils will flow out of the collecting pan and out the drain through the wall.

Then I cut the 2-3/4 hole in the wall for the plumbing and wiring – I had to get a hole saw for this. It’s a little scary to cut a hole like that in your wall! I lucked out in that it came out right next to the downspout so I could tie the pipes to the downspout.

Then I bent the pipes attached to the inside unit so they’d go straight out the hole when the unit was mounted, fed the attached cable out the hole, and carefully mounted it (takes two people). The pipes indeed went out the hole just fine, and the cables draped all the way to the ground and were long enough.

I attached the 25′ hose set (actually copper pipes with styrofoam sleeves) to the stubs sticking out of the wall, and carefully unwound them so both pipes, the cable, and the drain hose all came straight down the wall, and over to the outside unit. There was about 5′ more pipe than I needed, so I just made a little loop – rather than get tools to cut and flare the ends. The drain hose I left ending at the ground where it can just drip.

I had to wire up the outside unit – you really need an outside weather-proof disconnect box, and that was the hardest part for me – installing the conduit through the wall, making sure the wiring to the breaker box was good, and installing a dedicated 15 amp breaker. The cable from the outside unit to the disconnect box is fat – about 15mm, and I had to bore out the strain relief fitting to accommodate it. The cable from the inside unit, since it already had a Molex connector on it, would not fit in the strain relief fitting on the outside unit, so I installed it without. It just plugs together and supplies power to the inside unit, and control signals from inside to outside.

Connecting the refrigerant pipes is simple – I didn’t need the torque wrenches the instructions advised – just used a regular adjustable wrench, and you can feel pretty well when you have it tight enough. You pressure test the system by opening one of the valves (using a metric hex wrench) for a few seconds just 1/4 turn, then closing it, and checking each connection with soapy water. I had to cinch a few of them down a bit to get the bubbles to stop.

Here’s how you blow the air out of the system. Read the instructions, open the “liquid side” valve a few turns, then firmly press the Schrader valve on the “vacuum side” valve for 3-4 seconds. The air will blast out, and enough will be gone that it will work well. Then open both valves all the way (until the stops) for operation.

They supply two rolls of “tape” to wrap the hoses and cables with – but it’s really just like thin shower curtain vinyl, and if you drop the roll while you’re wrapping it, it completely unwinds all the way to the shrubbery below, and you have to wind it all up by hand. Just be prepared to be exasperated. I still have a second layer to go…

When I powered the whole thing up, nothing happened. I finally managed to open up the inside unit – you open the outer casing (to expose the filters), then remove five screws and pop off the middle casing (easier said than done, while standing on a step ladder!). The electronics is under a metal cover on the right, and after another screw I got that exposed. You can’t really get at the circuit board (it’s edgewise in the metal box, with no easy removal I could figure out), but I found that apparently the cable to the outside unit had pulled an inch or two, and one of the power connectors was pulled out of the circuit board. I couldn’t get any slack from the cable, so I made an extension and plugged it in. Replacing the middle casing is hard – it interferes with the vanes that direct the air and you still need to get it to hook at the top.

Then it worked!

It’s noisier than advertised, but it seems to cool (and heat) very nicely! Much of the noise seems to be from the slightly unbalanced squirrel cage fan, and various plastic things rattle a bit. It is a lot quieter than the old window air conditioner it’s replacing.

I’ll update more as I have some experience with it.