I'm looking at purchasing a Mini Split 24,000 BTU for a 1200 square foot cabin, single head unit. I have the line set (25')in place as well as the electrical disconect and 14-3 wire, also a drain line. My question is; are the Fujitsu mini splits good units? Is the remainder of the instalation a Do-It-Yourself project?

A 2 ton Fujitsu is almost certainly going to be oversized for a 1200' cabin, unless you're planning to stay there when it's -25F outside.  At +5F the AOU-24RLS2 puts out about 30,000BTU/hr, which is about the heat load at that temp of a 2400' code-min house. Every good heating/cooling system starts with a load calculation based on you window, wall, and attic U-factors/R-values and a reasonable outside design temp. Where is this cabin located (for climate data/outside design temperature), and what are your wall & attic square footages and R-values?

The 2-ton AOU-24RLS2 and the rest of the AOU- xxRLS2 series are pretty good units, but for climates where it regularly gets below -20C/-4F, the -RLS2-H series is probably better, with features specifically designed for true cold climate operation. (They have a full spec at -15F, but are still cranking away at outdoor temps well below that.)

Much or most of the installation can be done DIY, but for charging and testing the system you may want to hire a tech. I don't know if Fujitsus are normally sold with pre-charged linesets like some vendors, but those can leak during storage/shipping/installation, and not 100% guaranteed to be optimal every time. It's usually worth paying a factory trained tech to do the final commissioning & test.

In snow country always mount the outdoor unit where it won't be hit with roof avalanches/cornices (or build a shed-roof over it), and mount it high enough that it can't get buried by drifting snow. Many installers in my area are used to thinking of them as air conditioners, ignoring the wintertime facts of life, and the owner can end up digging them out multiple times per winter. Bracket mounting them high on exterior walls protected by overhanging eaves/rake of the roof is best-practice:

http://uphillhouse.files.wordpress.com/2011/07/ashp-1-2.jpg

http://www.quadomated.com/wp-content/uploads/2013/02/Fujitsu-Heat-Pump-012.jpg

Ground-mounting them too close to the avalanche path of a metal roof is not:

http://www.greenbuildingadvisor.com/sites/default/files/Montague%20house%20-%20minisplit%20compressor%20buried%20by%20snow.jpg

More here.

Mounting them on the wall of the home is hideous. I would find a spot on the ground that protects them from snow but wall mounting is plain butt ugly. That is what gives mini-spilts a bad name.

Also, hiding the electrical lines and refrigerant lines behind the exterior finish is the better approach, although I know retrofits make it harder to do. I am not a fan of steel conduits and white plastic vinyl panels running visible for all to see.

They were discussing on the Green Building Advisor forum that some "green energy" homes are the most hideous homes on the planet. Where bad taste trumps all. It's like they throw aesthetics out the window. A balanced approach is best. The go ugly and go green approach turns off about 90% of all future customers.

Posted By Lbear on 06 Jun 2013 03:30 PM
Mounting them on the wall of the home is hideous. I would find a spot on the ground that protects them from snow but wall mounting is plain butt ugly. That is what gives mini-spilts a bad name.

Come on now!  The outside appearance is only responsible for half of the ugly.  The other half is inside the house (not including the residents.)

I wasn't aware they made different seireis, I was looking at the 24 rlxfw system, it puts out 27,600 btu heating and 22,000 btu cooling. The building is in Northern Mn where it feels like we are still below zero today. The unit will be used for cooling summer and heating in the spring and fall, the building has slab heat for winter months. The building has R-50 in the ceiling and R-21 in the walls. The walls are 8' high and half of the 30' x 40' building has a vaulted ceiling. The line set ect. was put in before the walls were finished so everything is hidden. The outside unit should be OK on the ground under the 2' eves.

Posted By Lbear on 06 Jun 2013 03:30 PM
Mounting them on the wall of the home is hideous. I would find a spot on the ground that protects them from snow but wall mounting is plain butt ugly. That is what gives mini-spilts a bad name.

Also, hiding the electrical lines and refrigerant lines behind the exterior finish is the better approach, although I know retrofits make it harder to do. I am not a fan of steel conduits and white plastic vinyl panels running visible for all to see.

They were discussing on the Green Building Advisor forum that some "green energy" homes are the most hideous homes on the planet. Where bad taste trumps all. It's like they throw aesthetics out the window. A balanced approach is best. The go ugly and go green approach turns off about 90% of all future customers.

You probably don't live in areas where snow depths will often reach 3-4 feet every few years. (Those types of snowpacks don't happen every year where I live, but they happen more than once per decade.)  There's no such protected place on the ground at my house, and in deep snowpack years I will sometimes have to dig around the perimeter to keep snow off the bottom clapboards after a drifting Nor'Easter, despite 2' overhangs on the eaves everywhere.  On a big storm the drifts in the yard have hit 5', but not (yet) against the house, during my tenure there.

Most folks who do live in those climates find that they look pretty good when the snow's still about a foot below the bracket the morning after a big blow, and they didn't have dig the f'n' thing out during a 40 mph blizzard at 4AM and run the thing in air-conditioning mode for 15 minutes to clear snow out of the heat exchanger to keep warm.

You don't have to mount it on the front side of the house like some kind of hood ornament, but you definitely DON'T want to ground mount them in snow country.  I've seen them tucked away politely under taller porches well protected from snow-drift in Vermont. Most people put 'em in back, maybe screen 'em from views with arbor vitae or some tree that won't eat the house. (Snow country with deep snowpacks usually have sufficient water to sustain tall shrubberies.)  They mounted the one at the UpHill House  on the nearly windowless back side. The view from the driveway & road looks like this.  Some people think the PV blue roof look is butt-ugly too, but so what? At least they're not mounted at some cocked angle bracket to squeeze the last 1/4% out of production, but are parallel and proportional to the roof deck.  Not all elevation views need to be equally beautiful.

The oversized air-conditioning compressors peeking out behind the ocotillo in AZ side yards aren't exactly a thing of beauty either, but there are certain minimal practical aspects that need to be met in the name of comfort.  In snow country that means keeping the the mini-split out of the snow-drifts and cornice-falls. Bracket mounting on a wall under protective eaves is one way- it's a simple and practical way, but not the only way.  I have no problem with the aesthetics of bracket mounting when it's on the side you never see, but clearly YMMV.

Everyone says they look cool on a modern home.  In this location, they are away from the weather and accessible from the low roof in front.  I'd mount them on the wall up under the eaves every time.

Posted By Dana1 on 06 Jun 2013 06:25 PM
 They mounted the one at the UpHill House  on the nearly windowless back side. The view from the driveway & road looks like this.  Some people think the PV blue roof look is butt-ugly too, but so what? At least they're not mounted at some cocked angle bracket to squeeze the last 1/4% out of production, but are parallel and proportional to the roof deck.  Not all elevation views need to be equally beautiful.

Well, I guess if the house is a box then who cares where the thing goes? I am not alone in my vocalization about how some of these "green homes" lack any aesthetics, while others are just plain hideous. The GBA forum is discussing the issue/problem as I type this. It's like someone taking a high school drafting class comes up with these box designs as they can't design anything more complex than a square or rectangle. If the below home was designed by a real architect, they should be ashamed. I highly doubt it was designed by a true architect but one never knows.



The biggest complaint the mini-splits get from potential customers is that they look like the 1970's window mounted portable A/C units. When they are attached to an exterior wall this only emboldens their complaints. At least some mini-split companies are starting to get different colors besides WHITE boxes. LG units are probably the most aesthetically pleasing indoor units but they lack the reliability of units like Mitsubishi.

"Everyone says they look cool on a modern home. In this location, they are away from the weather and accessible from the low roof in front. I'd mount them on the wall up under the eaves every time."
Yeah in snow country you might not want to have the serviceman have to traverse a metal roof to get at the equipment....."slippery when wet"

I'd argue that when it comes to snow blockage, mounting them just above a very low slope roof is about the same (agreed, worse, accounting for access) as mounting them just above ground level. High enough to avoid snow and low enough to be hidden by well placed vegetation makes sense to me. And facing the road - that's just ugly IMO.

Boxes may not look great, but they are energy efficient and inexpensive to build.

There are snow and ice melters there to keep the roof clear of condensation. And that is not the front of the house. I's the back. It doesn't face the road.

It's a low-slope roof so it is easily walkable. Access is by ladder or through the window to the right. The servicemen actually participated in selection of the location.

I am not alone in my vocalization about how some of these "green homes" lack any aesthetics,

I recognize this picture as a classic New England antique style. Sometimes, it gets called a saltbox if it has a longer sloping roof or a "colonial". The form was driven by timberframe construction methods and is not unappealing. It is simple to build and efficient in the use of energy because of the usable volume. They are often selected as green builds because of that and because of the roof slope which is conducive to solar panels, sheds snow, etc.

Even though it is based on a "box", I don't find these unattractive. Look in any book of houseplans and you will find hundreds of variants. Certainly not like the hideous mcmansions that are often built today. I think it has something to do with roof lines or window placement and size ratios.

It's interesting how the modern updates like solar panels and the shades over the windows try to work with the classic style features.

Posted By jonr on 07 Jun 2013 08:41 AM
I'd argue that when it comes to snow blockage, mounting them just above a very low slope roof is about the same (agreed, worse, accounting for access) as mounting them just above ground level. And facing the road - that's just ugly (IMO).

Boxes may not look great, but they are energy efficient and inexpensive to build.

When building to Net Zero or PassiveHouse (like the UpHill House) on a budget, geometry matters. Sure the UpHill house is a "shoebox with a gable", but it's architecturally congruent with the traditions of that region going back a couple of centuries or more.

In the ~7200 HDD climate of Cambridge NY, with a lot of bump-outs, nested gables, and dormers you more than double the amount of thermally bridging corners, and create snow-trapping roof valleys.   There's are REASONS the shoebox w/gable became the standard New England/NewYork form factor- it's an appropriate and practical form for the climate, the way 3' overhang hipped roofs became the standard in Bangladesh, or 2' thick adobe walls in Texas.

The Beaton house in Shrewsbury, MA (~6800 HDD climate) has a bit more complexity than a total shoebox, but not too much, and the 2.5 ton multi-split compressor (2 heads, one per floor) is again mounted in rear where you don't have to look at it.  I don't remember how high off the ground it is, and couldn't find an online pic- IIRC it's on the west side of the house. Being a house builder/contractor Matt Beaton's costs were more on a wholesale level, and his budget was more open ended than some. His design probably would have had to be simplified for a retail buyer a tighter budget with PassiveHouse dreams. While this house won't be gracing the pages of Architectural Digest any time soon, it looks nicer than most of the houses in that neighborhood, which has a lot of simple ranches, raised-ranches & capes, plus few McMansions thrown in if you stray a few blocks from his Surrey Lane digs. Take a google maps street view tour of th' 'hood, he didn't over-build or under build from an local aesthetics point of view.  It's as nice or nicer looking than his neighbors' houses, but his utility bills are a tiny fraction of theirs. (I believe his is the house in the woods at the NW bend of Surrey Lane, with no real street view- you have to head up the driveway to get a good look.)

Posted By jkrash on 06 Jun 2013 06:01 PM
I wasn't aware they made different seireis, I was looking at the 24 rlxfw system, it puts out 27,600 btu heating and 22,000 btu cooling. The building is in Northern Mn where it feels like we are still below zero today. The unit will be used for cooling summer and heating in the spring and fall, the building has slab heat for winter months. The building has R-50 in the ceiling and R-21 in the walls. The walls are 8' high and half of the 30' x 40' building has a vaulted ceiling. The line set ect. was put in before the walls were finished so everything is hidden. The outside unit should be OK on the ground under the 2' eves.

Don't count on it not getting buried in snow drift in MN- it's not like the wind never blows there while it's snowing, eh?  I have 2' overhangs too, and it really wouldn't work to ground mount it for me.  You may need to provide some sort of wind-barrier/valence to keep the snow from choking it if you intend to run it during the snowy seasons.

I assume that's R21 batts in 2x6 framing?

What's the square footage of window/door (and the approximate U-factors)?

With the thermal bridging of the framing, with no exterior foam, a 2x6 wall w/R21s averages about R14-R15 (~U0.07). Assuming the R50 is between rafters with a 10-15% framing fraction, with thermal bridging the roof comes in at about U0.025.

With 8' walls and a 140' perimeter the gross wall area is about 1100', and at typical window fractions you're looking at 150-200' of window. Assuming two 22' doors call it 900' of wall, 45' of U0.5 door, and 155' of U0.3 window, for rough figurin'.

With a bit of pitch to it the roof probably comes in around 1500'.

In N.MN I'll assume a 99% outside design temp of -20F (like Hibbing?), and an interior design temp of 70F, for a 90F delta-T.

Window losses:

155' x 90F x U0.30= 4185 BTU/hr

Door losses:

45' x 90F x U0.5= 2025 BTU/hr

Wall losses:

900' x 90F x U0.07= 5670 BTU/hr

Roof losses:

1500' x 90F x U0.025= 3375 BTU/hr

Add it all up and you're at ~15000 BTU/hr, and that's at -20F.   Add 15% fudge-factor for infiltration and floor losses and you're still under 18K.

Do you really need 27.6K of heating capacity for just the shoulder seasons? (Methinks not!)

Do you really need 22,000BTU of cooling for ANY 1200' house, let alone one with an R50 roof and U0.30 windows? (Not likely!)

It's WAY oversized for a shoulder season load, and ridiculously oversized for the likely cooling load.

The AOU-15RLS2H puts out 15K at -15F, and would probably be able to carry the whole load, even on design-day with a bit of help from interior heat sources like a coupla sled dogs & sweaty humans playing video games on a big-screen TV, or a small amount of resistance heating.  It's still probably a bit oversized for the cooling load, but but so what?

If you're only using it for shoulder season heating the -12RLFW (same series as the -24RLXFW) would more than cut it, and would be better sized for your likely air conditioning loads (unless ALL of your windows are west-facing.)

It would be interesting to put numbers on the price differential and also the efficiency differences (they occur in both directions) for larger vs smaller inverter heat pumps.

LG has the right aesthetics in mind with their mini splits. As mentioned, if only their reliability was on-par with Mitsubishi, these things would sell a lot better. Hopefully Mitsubishi gets out of the white fly blower look and steps up with some modern looking wall units.

Lbear, You and I have exactly opposite senses of aesthetics. In my world an ideal house has 4 corners and a simple roofplan. The long axis faces south, and the east and west are shaded by deciduous trees. Use good windows and insulation and air sealing. Use day lighting and efficient lighting, good appliances and relax. No attached garage, or connected only by an open breezeway. I believe form is function, and it is a hell of a lot harder to build an livable small house than to throw square feet at a problem. No place to put your shoes? We will just add a 400 sf mudroom with cathedral ceilings. Need to eat lunch? Let see we can choose from the kitchen, breakfast nook, the informal eating nook or the formal dining room, or the bar or the rear deck or the front deck or the gazebo. Own a car? Well you better add a 4 -5 car attached garage in case you need to buy a Kubota tractor to mow your 1/3 acre property. I KNOW, we will put a bonus master bedroom over the garage so we can sniff exhaust fumes all night. Nothing makes me cringe like the current crop of mc mansions with 19 different roof planes and fake dormers. I would take a well built cape or ranch any day. YMMV Eric

Posted By eric anderson on 09 Jun 2013 12:31 PM
Lbear, You and I have exactly opposite senses of aesthetics. In my world an ideal house has 4 corners and a simple roofplan. The long axis faces south, and the east and west are shaded by deciduous trees. Use good windows and insulation and air sealing. Use day lighting and efficient lighting, good appliances and relax. No attached garage, or connected only by an open breezeway. I believe form is function, and it is a hell of a lot harder to build an livable small house than to throw square feet at a problem. No place to put your shoes? We will just add a 400 sf mudroom with cathedral ceilings. Need to eat lunch? Let see we can choose from the kitchen, breakfast nook, the informal eating nook or the formal dining room, or the bar or the rear deck or the front deck or the gazebo. Own a car? Well you better add a 4 -5 car attached garage in case you need to buy a Kubota tractor to mow your 1/3 acre property. I KNOW, we will put a bonus master bedroom over the garage so we can sniff exhaust fumes all night. Nothing makes me cringe like the current crop of mc mansions with 19 different roof planes and fake dormers. I would take a well built cape or ranch any day. YMMV Eric

Why does a home either have to fall into only 2 categories; a plain box or an inefficient McMansion? In addition, when people (and I am not alone, just read the GBA forums) comment on how some green homes are just plain ugly, some people immediately accuse them of wanting to build an inefficient gigantic home? This is where the green building world begins to self cannibalize and alienate itself from society. It's like saying that to be an environmentally minded you have to have dreads, not bathe, live in tents, smoke pot, and attend protests.

I agree, everyone has different tastes and that is what makes life exciting. As discussed on the Green Building Advisor website, many people are turned off by the idea of "green" because the homes they are shown that are "green" lack any visual interest, while others are just plain hideous. While a box might be the best use of space and some people like them, there are many others who don't. I agree that many of the modern day cookie cutter homes are inefficient and have fake dormers or fake shutters, etc. When a "green" home has 3 different siding types and colors attached, looks like a high school student drafted the thing, and lacks any visual interest, it's as if the ugliness is tolerated because it's an efficient home. A "go green and go ugly" slogan.

Why can't a home be both efficient and aesthetically pleasing without having to look like a shoebox and have white mini split units draped all over the side of the homes walls?
The answer is that IT CAN be designed to be both aesthetically pleasing and energy efficient. Although it requires more thought and better architects.

When these are touted as green home examples, how on earth will this appeal to the other 80% of people?

Even Martin Holladay from Green Building Advisor agrees that there is a problem: (emphasis mine)

"Malcolm,

Why can't a home be both efficient and aesthetically pleasing without having to look like a shoebox

I guess it is a matter of degree. To what degree are you willing to trade off aesthetics for performance? In most circumstances, as soon as you begin to depart from the box format, you start to lose efficiency. And then, there is the issue of cost. The more frills and curlicues you add, the more "unnecessary" costs appear.