Thinking of a mini-split

Discussion in 'The Garage' started by jad3675, May 13, 2013.

  1. jad3675

    jad3675 Been here awhile

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    My house is a 62 year old 2500 sqft Cape Cod with infloor radiant heating and no central AC. every summer, I lug out the 12K, 10K and 8K window ac units to provide our house with some sort of cooling. The windows units mostly work, apart from being noisy, heavy to install and not horribly efficient. I've put up with them for the past 5 summers, and I'm thinking about getting a mini-split system installed in the house.

    Fujitsu appears to be the brand that fits my needs/wants the best. I had three contractors come out and bid on the work; two came in at ~10K, and one came in at nearly 13K, all for the same work and equipment.

    All three quotes seemed a little high for a Mini install. Last year we had a quote done up for a high velocity unico system, and it came in at 13K. There was a lot more construction (and destruction) required for that install, and we'd lose two closets which is why we went after the mini split quotes. I had thought that a mini split install would be cheaper....

    I've spent the past few days putting together an online sourced parts list of what would be required to install the system. Everything (copper for line sets, AC disconnect and wiring, duct work, 45 degree flaring tool, line set insulation, lines set covers) would set me back 5K. Local mom and pop AC shop would charge me $200 to pressure test, vacuum, set R410A level and release the system for startup.

    Now, I'm not against paying someone for the work they perform, but I can do monkey work just as easily as the next guy and 5K is lot of money. Placing three indoor air units in the knee wall space doesn't take an advanced engineering degree, nor does placing the outdoor condenser.

    So, am I crazy to think to attempt this myself? Hell, am I stupid for thinking of spending 5k for the luxury of non-window unit AC?

    Anyone have any experience and/or opinions?

    John
    #1
  2. kfsinc

    kfsinc Chaingolian Observer

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    I sold and installed SpacePak, the original high velocity system. Here's a good(short) article. http://www.uniqueindoor.com/unico-spacepak-systems/

    And here's a pretty good story about self installing SpacePak: http://ths.gardenweb.com/forums/load/hvac/msg0721464625667.html

    It may be a little more expensive up front, but it will be less expensive to run and much less intrusive to install. Any way you cut it the mini-split systems look like add-ons. The small duct systems are virtually invisible, and provide significantly more comfort.

    I don't know your house layout, but you'll probably need multiple mini-splits, most likely one or two on the second floor and one or two on the first. One for each major room (bedrooms, Living room, Family room, kitchen) would be ideal.

    Again, don't know your layout, but losing two closets for Unico or SpacePak is not normal. I'd take a closer look at that before proceeding.

    You can certainly install SpacePak your self up to the final compressor hook-up.
    #2
  3. jad3675

    jad3675 Been here awhile

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    Hey, thanks for the info, I appreciate it.

    I should have pointed out that I want to use ducted mini-splits; the air handlers will be in the knee wall space, with ducts to the various rooms. I can't stand the wall hang units. The plan is for separate condensers on the left and right side of the house, each running 3 units for the various room.

    The layout of the house is odd - it's a large Cape with the second floor bisected by dormers on the front and back, so there's no command knee wall space between the left and right side of the house.

    I'll have to re-check the quote for the unico regarding closet space. I think they were using one on each floor to run a common drop. The common wall in the center of the house is unusable since it contains the copper for the radiant heat to the second floor.

    John


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  4. 1greenmachine

    1greenmachine Been here awhile

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    I'm pretty much in the same deal with hot water heat and looked at the Mitsubishi brand that is popular around here. I didn't have a dealer come out but I'm thinking probably gonna be at least 6 grand for just the units so I'm probably gonna be sweating for awhile.
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  5. zap2504

    zap2504 Dave E.

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    I'm a residential energy auditor and I hate Cape Cods! Have not seen one that did not leak air under the upstairs floor (from the knee wall area) or had exposed (or no) insulation in the knee wall, or had inadequate insulation in the sloped ceiling areas. And unless you insulated and air sealed the area behind the knee walls, placing air handlers in this space would make them work extra hard to provide cooled air (I hate attic AC handlers/ductwork too!). I would do work that would cut down your need for heat/AC first (go to Greenbuildingadvisor.com or and search for "cape cod" or go to energystar.gov and download their DIY manual). Then it would make sense to go to a mini-split system sized for your new requirements. Or by that time maybe an Energy Star-rated 5K BTU window unit would suffice.
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  6. jad3675

    jad3675 Been here awhile

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    Thanks, I was thinking of spray foam insulation at some point, or a DIY like outlined here:
    http://blog.energysmartohio.com/blog/bid/211267/How-to-Insulate-and-Ventilate-Knee-Wall-Attics

    John
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  7. zap2504

    zap2504 Dave E.

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    John,
    Good practical guidance for Cape Cods, and make sure to do all the air sealing work first before adding insulation (actually is 2 steps in 1 if you apply sealed foam insulation board).

    I'd add some more info that we tell every customer:
    Think of what is inside the conditioned space and what is outside; the boundary between the two is where the air sealing and thermal resistance is applied (e.g., any hatch into the knee wall area should be weather stripped and insulated like an outside door).

    Most insulating materials do not stop air flow; they need some form of air seal to keep air from passing from the conditioned space to the unconditioned space AND it needs air sealing to keep air from washing through it in the unconditioned area (i.e., the knee wall insulation needs an air-tight backing). Air passing through insulation degrades its R value.

    Today's recommendation for attic insulation levels (at least in the Eastern PA region where I am) is R-49 for retro work. This equates to about 14-15" of blown cellulose (best for flat areas) or fiberglass (very hard to properly install) which usually means you will not be able to use the behind-knee-wall area for storage unless you build a platform above the insulation level. It also means that the angled ceiling level will be very hard to properly insulate as there is just not enough space between the roof deck and the ceiling so you might want to think about (contractor-applied) spray foam for this area as foam has about R-6 per 1".
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  8. ADW

    ADW 'tard bike restos

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    I'm not an HVAC installer nor do I have the slightest bit of experience doing it. My only comment here is: seems like you could pay for a LOT of electricity to run your current units for the 5k you're thinking of spending for the upgrade. Heck, spend 1k to update all 3 window units to something newer/quieter/more efficient and you've still got 4k left over. That's enough for a decent used bike!
    #8
  9. jad3675

    jad3675 Been here awhile

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    Oh, they are newer window units, the oldest one is from 2010. I should add that I'm looking at heat pumps; so they'd provide heat also. Radiant heat is nice, don't get more wrong, but it takes a long time for the system to get up to temp.

    John
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  10. ttpete

    ttpete Rectum Non Bustibus

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    I have a family room that has no heat ducting. It was originally heated with a through wall gas heater and cooled with a through wall AC unit. I replaced both with a Grunaire heat pump unit. It heats just fine, even in zero weather.

    http://www.grunaire.com/
    #10