Planning mini split install in Dallas

[miketyler]

After a lot of reading, I am ready to pull the trigger on an AC system for my garage/loft space.

The structure faces north and is 39 x 28 sqft and is near Dallas. Built in 2004, its brick veneer and has finished walls with fiberglass batting and white fiberglass batting in the attic in the loft. The shop has 10ft ceilings while the loft has an 8ft ceiling, three dormer windows with sloped ceiling. The shop has two 9'x9' doors with 1/2" foam board with foil back. (R3.2)

I submitted my info to eComfort and total loads are 29222 and 15127 for cooling. Recommended equipment is a Mitsubishi 36k 18 seer multi zone heat pump with a 24k wall unit for shop and 9k wall unit for the loft.

With 1092 sqft per level the numbers work pretty close to the 1ton per 500sqft ballpark rule. The loft is under that perhaps for the sloped ceilings as it doesn't have the volume that a typical square room would have. It does have three dormers and also an open stairway for heat loss. Both floors are all open spaces.

So my questions are this:

• Should I bump the 9k loft unit for a 12k to be safe?

• Given the lowered amplitude in operation cycles with inverter technology, is it still possible to "over-cool" an area?

• I have decent attic access in the loft and was thinking of centrally located cassette install. I know it will be a more complex install for the drain but wondering what else I am missing

 

[miketyler]

Also open to other recommendations on equipment. Mitsubishi is one of the best out there but the package quoted is over $5k and was hoping to do DIY the install for closer to $3k

 

[Jackfre]

For the loft, position your evap as far from the staircase as you can. Otherwise the cool air will simply spill down the open staircase. You might want to consider one of the floor/wall mount evals up there. They are dual fan and would fit on the little pony wall between dormers. Much easier install and service I would think than a cassette. If you go cassette, they typically have a mini-pump built in that will pump about 18" of lift. From there you can gravity the drain.

I think you will be better off with two 12's rather than the single 24 in the lower level. Better air distribution/mixing=better comfort. It also gives you the option of running only one unit when you want. With the inverters I don't think you have to worry about overcooling. I've only seen it a couple times and that was when the contractor grossly oversized the unit, like a 39 in a space a 7 could have handled. I tell ya, you just can't dream this stuff up.

Over the years I have seen a lot of mini-split manuf in and out of the market. My own prejudiced perception on mshp's is that if you want support, stick with the major brands, Mitsu, Fujitsu & Daikin. The other side of prejudiced perception coin is that if you go with the cheaper brands, in the future you may have good luck with parts or they become throw away units. worldwide there are many markets where that is the norm.

Nice building btw!

 

[miketyler]

Thanks Jack, appreciate the insight. The detached garage was the decision maker for us when we bought the place.

I was considering a cassette install for the loft to place the cooling source closer to the center of the space. I would like to heat/cool the garage also but if it doesn't impose more expense and difficulty in installation. It seemed to me the more units you have the more plumbing and maintenance issues you would be inviting so was trying to keep it simple. Garage has three of the Gossamer-style ceiling fans.

 

[miketyler]

You might want to consider one of the floor/wall mount evals up there.

I just looked these up and seems like they might be a fit. It doesn't look like they are as popular as wall and cassette installs and would limit my choices for mfr.

 

[patrickoneal]

Are you looking to heat or just cool?

I looked at the multizone systems for my house, as I wanted to cool two bedrooms. It's actually less money to buy two completely separate single zone systems, and when I looked at the charts the single zone systems are more efficient than the multihead systems.

My upstairs bedrooms aren't all that well insulated, and it's a 1 1/2 story cape cod style house. I was leaning toward a 9k system for each of the two bedrooms, but 12k systems were less than $200 more and the capacity of the 9k and the 12k at low speed is 4400 BTUs for the Daikin equipment I bought. I figured I'd be better off spending an extra $350 or so and end up with excess capacity at the top end and no danger of "overcooling".

For reference the 18 Seer 12k Daikin systems I bought were right under $800 each from a local supply house. If you went with two heads downstairs, three of those systems would keep you cool. If you want heat, it's obviously going to be more money.

 

[patrickoneal]

I noticed you have a little home theater setup up there. Those projectors will put out some heat, but probably not enough to worry about especially if you go with a 12k system.

On another topic, if you want to black out those windows, I got the older version of these shades for my home theater and they're fantastic(no light around the edges):

http://www.comfortex.com/slumbershades/slumbershades_cellular_features.php

If I recall, I actually got a tax rebate because they're rated as an insulation product and they significantly cut the draft from my old windows before I replaced them.

 

[miketyler]

Thanks for the responses, I was thinking less is more when it comes to equipment maintenance but hadn't looked at costs for separate units. I'd still be in for 24k load for the garage. Will need to shop that around. I want to heat and cool both spaces.

I blanked out the window behind the screen using the 1/2" foam board painted black, a thin layer of fiberglass batting and then sheet rocked over that. Those Comfortex shades look really slick. I will have to look into those as I had planned to build shadow boxes for double sided movie posters. We really only would use the space during the evening and it would still let enough light come in to keep you from tripping over things. Will have to check those out for sure. Were they pricey?

 

[patrickoneal]

Thanks for the responses, I was thinking less is more when it comes to equipment maintenance but hadn't looked at costs for separate units. I'd still be in for 24k load for the garage. Will need to shop that around. I want to heat and cool both spaces.

I blanked out the window behind the screen using the 1/2" foam board painted black, a thin layer of fiberglass batting and then sheet rocked over that. Those Comfortex shades look really slick. I will have to look into those as I had planned to build shadow boxes for double sided movie posters. We really only would use the space during the evening and it would still let enough light come in to keep you from tripping over things. Will have to check those out for sure. Were they pricey?

They weren't too bad:

Width: 47 1/4"
Height: 52 1/4"
Qty: 1
Unit Price: $145

Width: 23"
Height: 52 1/4"
Qty: 2
Unit Price: $98

That was back in 2010, and the company I bought from is no longer in business. Mine are the comfortrack(from the same company), similar to the newer "slumbershades", but I had to apply photographic blackout tape to the inside of the tracks myself because they would glow during the day. They've solved that problem with the slumbershades. I'll be getting a set of those if mine ever wear out.

As for shopping around for the mini split, if you have a contractor friend try to get them to open a cash account at United Refrigeration or Johnstone Supply or see if either will sell over the counter to you. I wouldn't expect any hand-holding at a supply house, walk in and ask for exactly what you're looking for and you'll have better luck getting them to sell to you. United has better prices on Daikin around here, at least for me. If they want you to show an EPA card, ask them if you can buy a test kit and sit for an exam. It's worth the hassle if you have the time, the prices online seem to be anywhere from 30% to 100% higher than you can buy locally.

 

[miketyler]

Good info, I thought pricing was better online even with shipping but I will check into that. There is a Johnstone and United Refrigeration both in my area.

 

[Falcon67]

We can do with a little less out here west of you because we tend to be dryer (well, maybe not THIS year LOL). I think keeping the lower half cooled will reduce the load on the upper floor. However, having lived in Fort Worth previously for 40+ years I know it gets hot, so a 12K up there would not be out of line IMHO. My shop is 24x40x8 ceiling and I'd do well with a 12K in the larger section (28x24) and a 9K in the smaller - if I was to go mini-split. I keep comfy now with a 11K + 8K, but we typically run 30% less RH than Dallas, or more.

 

[miketyler]

I thought the same thing about the collateral affect of a conditioned lower floor on the upper floor. I do worry about heat loss from the big roll up doors and multiple windows but maybe their calcs are intentionally higher since there is little penalty for over cooling with inverter systems. But the rest of the space should be as tight as my house, save the foam insulation on the exterior walls.

I like the look of the floor units but would be a bit more difficult running lines thru the floor beams. Looks like Fujitsu may be the only one that has them. I 'd like to place the condenser on the east facing wall. Power comes in on that side of the structure providing for a shorter power run. Also its shaded in the evening on that side and it doesn't have a lot of visibility.

 

[Falcon67]

I have a cheap steel 16x7 door on the shop (Clopay). The door faces south. The sig pic shows some shade but most of that tree is gone now to clear the doorway. I insulated it with 1/2" foil backed Styrofoam cut from sheets. Out side I have decent weather strip. It's surprising how well that seems to work on cutting heat - and cold - from coming through the door.

 

[Micscience]

Do you live in your garage? After seeing your garage there is no need to have a seperate house good luck and nice garage.

 

[85mcss]

SUPER sweet shop! I'd love to find something in north Dallas like that.

 

[miketyler]

Thanks, i dont live out there but might if I got some AC going.

I am still looking for a system and prefer a single multi zone system. I found that many of the more economy class multi zone splits can only handle up to 18k btu per zone. At least thats the case for Pioneer. I really would like to find a 36k unit that would support a 24k wall unit and 12k ceiling cassette. I think Thermocore has a compatible unit but I dont know the brand that well.

Her's a pic of mine with my insulated doors.

 

[72Anthony]

I think the cassette units are very expensive compared to the regular wall mount units...last time I looked was about a year ago. Maybe they don't manufacture that many or are geared to commercial installations.

A single wall mount unit may not provide enough circulation without having some fans.

 

[miketyler]

The space is all open and I have three ceiling fans in there. I dont mind placing fans where needed to distribute conditioned air.

On another note, after getting some rough numbers on equipment it seems the multi zone scenario will cost me 35-40% more than separate units. I am now thinking on separate units and while the loft seems easy, the load calcs for the floor level now seem off to me. The manual J for the floor space came in at 20k htg and 8k cooling while the loft calcs were much closer together. What would be the explanation for the disparity?

 

[miketyler]

Picked this up today, hope I dont regret doing this.

 

[miketyler]

And this

 

[Falcon67]

The bottom floor of the tower at the drag strip has a Mr Slim 24K, very quiet and works well. And it's hard to keep that space decent because there's a ton of in/out the door for run cards, payouts and such.

If I set the 10.5K to trip off about 4:30~5 with the one ceiling fan running on medium, it's decent (mid/low 80s) by the time I get out there at 6 or so. That's pretty good I reckon for a building that has heat soaked all day. That's 684 sq/ft and you know how it's been outside lately. It's nearly as sticky here and your are there. Dew points are way up, in the 60s. I also use once of those 48" vertical fans to help in the work area (240 sq/ft). The 8K does well but moving the air around makes it a lot better.

 

[miketyler]

Thats good to know.

Given the pricing I was getting on what I really wanted I opted for this Craigslist deal. This is a 1.5ton BTU heatpump that has a minimum capacity of 8k. Apparently I can control each of the shutters independently and direct the air where I want it. Perfect for directing conditioned air away from the stair case.

I plan to disassemble it this weekend to clean it. Its not that dirty but just want to recondition before I put it back in service. The inside evaporator does look dirtier than it should be and it looks like that even with filter in place, unfiltered air and particles could easily get past it.

I have to buy the remote and receiver for it as it only came with wired control. The cassette is a monster at about 3ft x 3ft square. I will have to get creative with my rafters and frame in a space for it. Also, looks like they had used a branch duct that I will need to block off.

 

[Falcon67]

If you got a good price on it, I'll bet it works out well. I like the idea behind those cassette units.

 

[miketyler]

picked it up for $700 (firm) and had to drive to West, TX to pick it up. There are a few parts I need to buy for it including the wireless received and remote. I spent an hour or so running the fin comb over the condenser though it really wasn't bad. The cassette wont be so easy to clean.

I am interested in feedback on the Mitsubishi cassettes and maintenance. Each vane has its own stepper motor and can be controlled individually. I read in the spec sheet that in heat mode those vanes open and close in pairs to alternate heat distribution. Framing in the loft for it will no doubt present challenges. I plan to install two power runs this weekend, the second for the floor when I decide to do it later.

 

[miketyler]

My cleaning project turned into a full scale disassemble of the cassette ceiling unit. The nice thing about it was that is comes apart relatively easy and clean up was pretty simple as well. I would bet many of the units out there are probably clones of the Mitsubishi design. Will post up pics to give you an idea of how Mitsubishi is building their units.

 

[Falcon67]

My grand dad used to drive from Whitney to West to buy beer since Hill County was dry. Sounds like an interesting puzzle.

 

[miketyler]

Since it seems there is little for illustrations on these, thought I would post up some pics of mine that I took during disassembly. First pics shows how I bought it. Next was with four covers located in each corner that expose the four bolts that hold the cover on. FYI, if you add wireless remote control, one of the covers is replaced with a unit that has wireless receiver eye integrated in to it.

 

[miketyler]

Next pic shows the PCB case and shroud cover removed. This thing was dirtier than I expected and suspect it may have been run without the filter. Filter is intact with no cuts. I didnt have anything to scale it by but the blower fan is pretty large with pitched blades. Interesting design...

 

[miketyler]

Initially this is was as far as I planned to go but with the plastic shroud off and fan removed, I could see the evaporator had substantial build up and after a few minutes decided it needed to come out to get cleaned proper. So I removed the styro-foam drip condensate pan to get access to the evaporator core.

 

[miketyler]

With the drip pan out, I can see the condensate pump and float switch. The pump is rated to 33" lift. The drip pan has a special coating in the drip area that seals it. As you can see in the before and after, it cleaned up nicely

 

[miketyler]

Evaporator comes out with a few screws. The fin pitch is very fine, finer than my trim comb has. Had to be very delicate with it but once out I carefully cleaned it with Simple Green and a soft brush.

 

[miketyler]

With the evaporator out and the top of the chamber cleaned, I needed to block the branch duct used in the previous install. Some of the purple thermal foam made a nice plug. The chamber should be air tight so I spray foamed it on the outside as well. Later determined I got a little carried away with and had forgot about the crazy expansive properties of the product. I fabricated a cover plate and used double weather strip to seal it.

 

[miketyler]

Hole plugged, parts and core cleaned and ready to go back together.

 

[Falcon67]

Well done there.

 

[Wakepowell]

Keep us posted on how your installation goes. I also live in the DFW Area. This week I purchased two 36,000 BTU M-Series Mitsubishi systems for my 3,900 sf garage. When sizing the systems the requirements varied from 50,000 BTU’s to 75,000 BTU’s. My research also led to concerns that over sizing the system could result in insufficient dehumidification.

As you can see from the attached picture, my area is very open. I am concerned at how well the air will disperse. I may end up putting 2 Big *** Fans in to help.

 

[Falcon67]

Air circulation helps a bunch. That's mainly how a 10K can keep it decent where I park the cars. That's 672 sq/ft, 8' ceiling. I use a cheap 42" ceiling fan - may add another on the other side later if I find one cheap, cheap. My "design" is such that except for things like brake or chassis work, major assemblies like engines or transmissions can be extracted in the parking section, then moved to the work room where it's quick and inexpensive to heat or cool the work space.

 

[pseudorealityx]

Keep us posted on how your installation goes. I also live in the DFW Area. This week I purchased two 36,000 BTU M-Series Mitsubishi systems for my 3,900 sf garage. When sizing the systems the requirements varied from 50,000 BTU’s to 75,000 BTU’s. My research also led to concerns that over sizing the system could result in insufficient dehumidification.

As you can see from the attached picture, my area is very open. I am concerned at how well the air will disperse. I may end up putting 2 Big *** Fans in to help.

If you're going to use an 'actual' Big *** Fan, even with your space, I'd suggest going larger rather than 2 smaller.

 

[miketyler]

Air distribution for the loft was my main concern and the motivation behind going with the more difficult cassette installation. The easy way out would have been to place a wall unit at top of the stairs and add a fan to ensure delivery to the far end of the room.

I don't think you can go wrong with the Mitsubishi equipment and from what I have read, its nearly impossible to oversize with mini splits and experience rapid cooling and residual humidity that you might see with a conventional system. The larger capacity inverter systems do have a rated minimum and I would pay attention to that number when sizing.

 

[Bwprince]

Looking good Mike, now git er' done! You'll have to fly out to Atlanta and help me get mine in when its ready for air.

Oh yea, and get back to work! ;-)

 

[miketyler]

Hey Bob! By the time I am done with both of mine I'll be a pro.

WakePowell - thats one helluva space you have there. My brother has a Shelby replica as well. Was built by BackDraft Racing out of FL. He ordered it with their wicked 427 package. I rode with him once and wont do it again.

He enjoyed the buying experience. Once a deposit was made and the car assigned a serial he could login to the website and check progress on the car during the build. He flew down there for final assembly.