Buying and installing a mini split air conditioner: your advice?
April 22, 2013 11:30 AM   Subscribe

Help me get a jump on the summer with a new, single room air conditioner.

The air conditioner will be for a single room--our bedroom--so ductwork will not be involved. (The windows are Andersen casement-style, so a window unit isn't doable.) Since the bedroom's on the second floor, my idea is to place the condenser part of the unit on a first floor deck, and run the piping and electrical vertically up the house's exterior wall--in a conduit, if possible-- till it reaches the second floor. Then, we'd drill through the siding and interior Sheetrock and place the interior unit at a point around 8' above the floor. Since the condensor will be on a lower floor, hopefully we'll benefit from increased quietness.

My questions and concerns:
1) Executing my installation plan will require about sixteen feet of piping and wiring to get to the second floor. Do most installation kits contain this amount of materials? In general, is this a feasible plan?
2) BTU calculations. The room is 255 sq ft, with a ten-foot peaked ceiling, and located on the second floor with a southern exposure. This would seem to spell lots of late-afternoon heat. However, the mercury rarely climbs above 85 in my neck of the woods. This BTU calculator suggests that 9,000 BTUs would be sufficient. Do you agree?
3) Purchase decisions. What makes and models of mini split air conditioners offer the best results based on electrical efficiency and quietness at night?
4) Installation. I'm hoping to buy the unit online and hire a pro to do the work. Should I call an HVAC company or an electrician? What would be a ballpark price for an installation like the above, assuming three or four hours is involved?
posted by Gordion Knott to Home & Garden (8 answers total) 1 user marked this as a favorite
They do make casement window units. Is there something about your particular style of casement window that make a casement unit not possible?
posted by jmsta at 11:40 AM on April 22, 2013

I can only speak to #3: I bought an LG Art Cool 9,000 BTU unit for my workshop, it's huge overkill for my 285 square feet, can bring the shop from unheated freezing (for the few days that it gets that cold in coastal Northern California) to 70°F in a few minutes, although insulation calculations are very building specific. I paid a bit over $2k installed. Sucker is quiet and appears to be pretty darned efficient.

(Although looking at online prices right now I think I massively overpaid for installation. On the other hand, it got the city off my back re Title 24 compliance, and the guy who did it has since also stopped by to check out our house heater and not charge for the stop, so...)
posted by straw at 11:47 AM on April 22, 2013

Response by poster: They do make casement window units. Is there something about your particular style of casement window that make a casement unit not possible?
Not really, but if all things are the same, I'd prefer to keep the unit out of the casement window area (because the windows lead to a view of the woods which I'd like to keep unobstructed).
posted by Gordion Knott at 11:59 AM on April 22, 2013

>> 255 sq ft, with a ten-foot peaked ceiling

With a ceiling that high, consider the cubic footage. Sounds like there will be a lot of open space that will need to be figured into the BTU considerations. (not that 10' is a cathedral, but you know).

Also, in previous AC setups over the years, another thing that I have always screwed up by not giving enough consideration to was the southern exposure. Had I done so, I would have opted for units that were of a capacity of at least 10% greater than the calculators told me was fine.
posted by lampshade at 12:15 PM on April 22, 2013

It is likely that an HVAC professional can buy the same equipment at prices similar to, or more likely lower than, what you can find online, from local distributors - which also saves on shipping.

You might consider getting an HVAC professional in the mix right now for a quote. To get a better price, do some homework as you're doing, but also figure out a casement window solution, then approach an HVAC contractor for a quote on your mini split (play dumb and don't mention any research you've done on the mini split). They may feel some pressure to keep their quote low if they know that a casement unit is a reasonable solution that you are likely to go with.

Right or wrong, many professionals do not like customers who try to circumvent the normal quoting and purchasing process in order to score a better deal on the unit.

Further, if they supply the unit and something is wrong with it, it is totally on them to deal with it. What happens if you get a unit from, let's say, Amazon, and something is bent or broken?
posted by jgreco at 12:33 PM on April 22, 2013

Is it your house, not a rental? You could put the AC unit through an exterior wall instead of a window. Motels do this often for the same reason you have - to save a view and natural light. Be sure to ask the appliance dealer if this is possible with the unit you want. An experienced carpenter would be a wise investment if you are going to cut into a wall. The hole needs to be lined to prevent moisture getting into the insulation. Also be sure to install some sort of padding - AC units can vibrate.
posted by Cranberry at 12:49 PM on April 22, 2013

Should I call an HVAC company or an electrician?

You need both but usually the HVAC company will have someone they call or like to work with so call them first.

Your profile doesn't say where you are Gordion Knott but note that in Canada you'd need an outlet for service equipment located next to the condensing unit. So if you don't have a receptacle there already you'll be running two circuits not one.

Thru the wall A/C units are generally much more expensive than window units and though you see windows units installed thru the wall they aren't really designed for it and that causes problems. The reason hotels use thru the wall units is service can be done remotely so when a unit's A/C fails the hotel can just swap it out for a spare in just a few minutes and the room remains occupied.
posted by Mitheral at 1:34 PM on April 22, 2013

I did a similar project two years ago, and am really happy with the split (ductless) system. With the right unit & install it can be incredibly quiet and energy-efficient. I bought my system online, installed the outdoor and indoor units (2, in my case) myself, then hired an A/C guy and an electrician to do those aspects of the project.

What might be difficult is getting an HVAC guy that is willing to install a unit you find you better talk to HVAC installers first and see if you can find one that will work with you. The HVAC guy will likely have an electrician in mind to do that aspect of the work.

My answers:
1) Yes, feasible. You can buy piping kits that come in increments of 25 or 50 feet. Make sure the split system you buy is spec'd to "drive" the length of piping you need. You'll have to take a very exacting measurement of the route the piping will run, then get a piping set that is at least as long as this; hopefully with a few feet to spare. If you measure 19 foot from the outdoor unit location to the interior wall on which the unit will hang, get a 25 foot piping set, and the excess can simply be coiled near the outdoor unit. This eliminates the need to braze tubing connectors to get a custom length. For wiring, you will have to get the installation manual for the unit you are considering, and closely go over the electrical requirements they mention. The wire gauge depends on the unit size, and there will be other requirements for circuit breakers and safety shutoffs (indoor and outdoor) recommended by the manufacturer and perhaps required by your local electrical code. An initial consult with an electrician (have the installation manual available) is a smart thing to do before you go forward.
2) The BTU calcs are pretty standard stuff...if you call an HVAC person up-front, they will size the unit for you. Make sure you point out anything that would affect the A/C load: high ceiling, the exposure, the window, proximity to a kitchen, etc. You can also call the companies that sell these units online and get them to review your calculations, which they will be happy to do. You don't want to get a unit much larger than what the calculations indicate because an oversized unit can end up cooling the space so quickly that it will cycle frequently, shortening its life.
3) Some manufacturers will not sell their units to homeowners; they can only be obtained via an installer. But that's OK, there are many high-quality units that can be obtained directly. If you are good with The Google, you will find SEER ratings for different units that should give you an idea of which units have the best efficiency. The other tip I will give you is to hit the online forums for A/C professionals...if you spend a few hours reading these forums you will quickly get a sense of how the ductless systems from various manufacturers are viewed in terms of quality, reliability, ease-of-installation, etc.
4) I would educate myself a bit online via the pro A/C forums, then talk to a local HVAC guy. You might be able to get a ballpark estimate from the online forums (Terry Love's site is one I remember, there are probably others) and some advice that will let you know if your local installer is trustworthy or blowing smoke. The electrical install could take the better part of a day, the coolant/HVAC bit a half of a day. The physical installation of the unit is hard to estimate without knowing details.
posted by superelastic at 2:42 PM on April 22, 2013

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