Mini-split AC questions

rvr6000 · May 3, 2012

Long story short, the misses and I live in a 1 1/2 story home. Our bedroom encompasses the whole upper level (about 400sq ft). We're tired of the old window unit we put in every year (drug it in from the shed again today) to help keep it cool up there and have been talking about getting a mini-split ac system.

I would consider myself fairly mechanically inclined - Is this something I could tackle myself? I'm lucky in that where the indoor unit would be located is directly above where the compressor would be so no crazy line-set issues that I can foresee.

Speaking of the line-set, since it's gonna be visible from the outside, do these things just look like hell or is there a way to conceal them from view?

Power - If I understand what I have seen and read, the indoor unit gets it's power from the outside compressor? No need to run a special circuit or plug the inside unit into a wall outlet? Just have to run a circuit (240volt I assume) to the compressor.

Which model - always up for debate but what model/manufacturer do you guys recommend?

Thanks in advance for all your help.

green.bubbly · May 3, 2012

Installation is pretty straight forwards if you have any basic construction experience. Most units come with flared linesets so there is no need to braze or solder. I would suggest calling in a professional AC person to vacuum the lines and set the charges correctly.

There are lineset covers that conceal the linesets with a plastic channel. Not the best looking thing but not the worst either. Depending on the size of the unit, you would typically run the 120 or 240 power to the outside unit which then powers the inside unit.

I installed a cheap Klimaire last year in my garage and it seems to be doing fine but one year is not a good test. Depending on how much you will be running it, there are the cheapo inefficient models and then there are the more expensive high efficiency units.

Do a search, there are several threads on this topic with lots of great info.

Here is a good thread...

http://garagejournal.com/forum/showthread.php?t=94308&highlight=split

rvr6000 · May 3, 2012

Thanks, Green. I was wondering about those line-sets if they needed brazing or not. Have been reading that post my mpire too. Good info.

ghnl · May 3, 2012

The installation is not difficult. I agree that paying an HVAC tech to vacuum the lines (and adding refrigerant if needed) is a Good Idea.

They make line set covers (expensive for what they are however). I used a length of downspout (rain gutter stuff) and modified a clothes dryer vent for the top.

JakeKohl · May 3, 2012

If you are skilled with electrical and mechanical, getting the units in place is not very difficult. The tricky bits come in to play when you need to shorten the linesets and evacuate / charge the system. Unless you have some attic space to run the extra copper lineset, you will probably need to trim to fit. I've also heard that it's not wise to trust the factory flare on the purchased line sets. R410A that all of the split units are charged with now is very sensitive to a proper charge and it needs to be right to get the efficiencies out of the system. Hiring someone to come in and make the final connections, evacuate the system, and adjust the charge shouldn't be very costly if you've done everything else.

I've got two 18k btu split heat pump units that I'm in the process of installing and I've learned a bit. I've got an enough HVAC and engineering background to be dangerous but I have the manifold set and vacuum equipment to complete installation so I feel that this is within my reach. A couple of key items to consider:

The flare on 410A systems is a 45 degree flare and requires a specific flare kit - not the 60 degree flare commonly used elsewhere
the charge of the unit should idealy be adjusted to include the length of the lineset. Most systems are precharged for 25 feet. If longer, you need to add refrigerant. If shorter, you need to remove refrigerant.
Indoor unit is typically powered by the outdoor unit through an 18 guage 4 or 5 conductor cable so the only romex you need to pull is to the outdoor unit.
ghnl is right, they do make covers including nice 90 degree through-wall fittings - but they are stupidly expensive. Short of using gutter downspout or running the linesets in the interior wall (like I did since I had full interior access at the time), there aren't many other options.
dryer vents and a little spray foam make great wall penetration points for the lineset!

rvr6000 · May 3, 2012

ghnl: If you didn't tell me what those covers really were I never would've guessed. They look factory made.

Jake: I wouldn't have any problem setting the compressor and doing the electrical. The more I think about it I could just call the guy who installed my furnace last year and have him make the final connections. He's easy going, does nice work and I'm sure wouldn't mind doing something like that for cash. By the way, your install looks very nice.

JakeKohl · May 4, 2012

rvr6000, thanks for the compliment.

ghnl, I just realized you DID use gutter downspout - had to look closely! That looks great.

bigdav160 · May 4, 2012

I installed a Sanyo Inverter mini split in our extra large master bedroom. (900 sq/ft)

The hardest part with my install was running the romex. Like Jake I built brackets to hold the condenser unit. Even though I have a quality flare tool, my flares leaked. I went back and soldered the lines and recharged.

The unit works great and I no longer have to cool 3000 sq/ft to make the bedroom comfortable.

Highbeam · May 4, 2012

With such nice exterior unit installations could you folks show us the interior side? If the inside units could look good, then I think that these things would become more mainstream. Don't forget about condensate, you need to drain that from the indoor units too.

JakeKohl · May 4, 2012

Highbeam said:
With such nice exterior unit installations could you folks show us the interior side? If the inside units could look good, then I think that these things would become more mainstream. Don't forget about condensate, you need to drain that from the indoor units too.

I haven't gotten that far yet - hoping to start installing the interior units next weekend...which, in my case, is a little tricky. Because my linesets (and drainlines) are run inside the wall, I need to (ideally) make all of these connections before the insulation and dry wall are installed. However, the interior units mount on the surface of the drywall. So my choice is to do insulation and drywall and then cut out access panels to get to the connection points, or hang just enough insulation and drywall to mount the unit but leaving the connection points (later to be enclosed in the wall) exposed while I finalize installation. I'm going with the latter plan and if I have any issues, I can cut in the access panels later (hopefully the inspector won't have an issue with this method).

In the case of my downstairs/garage unit, it mounts to a wall that has attic access behind it from the original building structure...so that part is much easier and the connections can just be made in the attic.

ghnl · May 4, 2012

Highbeam said:
...could you folks show us the interior side?

Very unobtrusive and quiet. No louder than a small fan.

green.bubbly · May 4, 2012

JakeKohl said:
I haven't gotten that far yet - hoping to start installing the interior units next weekend...which, in my case, is a little tricky. Because my linesets (and drainlines) are run inside the wall, I need to (ideally) make all of these connections before the insulation and dry wall are installed. However, the interior units mount on the surface of the drywall. So my choice is to do insulation and drywall and then cut out access panels to get to the connection points, or hang just enough insulation and drywall to mount the unit but leaving the connection points (later to be enclosed in the wall) exposed while I finalize installation. I'm going with the latter plan and if I have any issues, I can cut in the access panels later (hopefully the inspector won't have an issue with this method).

In the case of my downstairs/garage unit, it mounts to a wall that has attic access behind it from the original building structure...so that part is much easier and the connections can just be made in the attic.

Good looking install. I see you have a couple more units in your garage.

I did the same thing you want to do with running the lineset and grain line in the wall when I did my garage. I was a pain in the but since I was putting OSB sheets on my wall. I cut out an access panel as well below my unit so I could connect the lineset and drain.

JakeKohl · May 4, 2012

green.bubbly said:
Good looking install. I see you have a couple more units in your garage.

I did the same thing you want to do with running the lineset and grain line in the wall when I did my garage. I was a pain in the but since I was putting OSB sheets on my wall. I cut out an access panel as well below my unit so I could connect the lineset and drain.

You caught me... I started with 12k btu units but later got nervous that I didn't include enough safety factor in my load calcs. I upgraded to 18k btu heat pumps instead. The one ton units are sold to a new home and headed there this weekend.

RKA · May 8, 2012

Good looking install Jake! My suggestion is to sheetrock where you'll be mounting the indoor unit and hang it, make the connections and pressure test with nitrogen. Once you're certain everything is good n tight, close up the walls

flybefree · May 9, 2012

I bought my mitu unit online and payed local guy $500 to install, came in way under the full quotes I had and I still have a valid warranty.

Shaun

Mini-split AC questions

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