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Wife wants mini-split for bedroom/hallway, options

Post in 'It's a Gas!' started by mass_burner, Apr 3, 2014.

  1. mass_burner

    mass_burner Minister of Fire

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    Okay, so she wants this for those rare occasions when heat/humidity get so bad we need an AC. We have awning windows, so window unti not an option. I would like a unit to heat also, in winter I run wood stoves in the main living areas, LR/KIT, family room, DR all open floor plan, the furnace for these zones barely ever comes on. At night we close the one door separating the "common area" from the bedrooms/bathrooms. Overnight in this area is where we use most of the oil.

    Do MS's do a good job of cooling and heating? Would electric be preferable to gas?

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  2. AK13

    AK13 Burning Hunk

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    Do you heat with natural gas or propane? Based on current prices in our area the natural gas is most likely cheaper than heat pump. If propane, then heat pumps for sure.

    I would get a heat pump vs. cooling only unit anyway though. The heat pump hardly costs any more than cooling only and would be ideal for shoulder season heating and maybe even cheaper than natural gas when temps are in the 40's and above.

    If you want maximum heating performance then Mitsuibshi Hyperheat is the way to go. If low temp heating isn't a priority then a unit from Mitsubishi, Fujitsu or Daikin would be my recommendation. IMO those are the top tier brands.
  3. mass_burner

    mass_burner Minister of Fire

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    We have NG hookup, but only use it for cooking, but its there. No propane.
    Last edited: Apr 3, 2014
  4. AK13

    AK13 Burning Hunk

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    Yikes, you have NG in the house and you are burning oil! I bet you'd have a very good payback to swap out your oil furnace for an NG one.

    A mini-split heat pump would still be a nice way to add A/C to the house. But in terms of a payback your best "investment" would be to heat with NG instead of oil.

    How do you heat your hot water?
  5. mass_burner

    mass_burner Minister of Fire

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    The PO upgraded to a new Buderus burner/storage tank in 2007. Estimate to switch to NG, even with subsidiies, was 14k. I couldn't see ripping out a very efficient burner and paying 14k to do it. I put in another insert instead. I've used 215 gals since 11/5/13, probably can make it to 11/5/14 with 50 more gals. Hot water with oil too, but that takes very little.

    Does a heat pump have to run on propane?
  6. Joful

    Joful Minister of Fire

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    I have installed a few minisplits, all Mitsubishi. I have one heating and cooling my music studio right now, with auto change-over. They do the job, and they're about as efficient as any other heat pump option. A propane or nat.gas backup is NOT an option with Mitsubishi, but perhaps others. They do have some nice hidden ceiling, wall, and toe-kick indoor units / evaporators, in addition to the standard wall mounted units. I'm sort of wishing I had done a ceiling mounted unit or two in my most recent install, instead of the standard wall unit, but I don't have much experience with those.

    One issue with any minisplit is the drain. Installers have told me they want a pretty aggressive and continuous downward slope on that drain. I don't know why, but suspect they must have had some drain issues in the past.
  7. maple1

    maple1 Minister of Fire

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    Heat pumps run on electricity.
  8. AK13

    AK13 Burning Hunk

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    Ahh, I see. You don't have a furnace. You have a boiler. Furnaces heat air. $14k sounds very steep. But regardless if you are only burning 200+ gallons of oil a year then I agree that there is not a reason to swap out a nice Buderus boiler.

    Condensate drains can be an issue for some installs.If you are on an exterior wall then its easy. If on an interior wall and over basement then probably easy since you can go down the wall and find a place to tie in in the basement (laundry standpipe, etc).
  9. mass_burner

    mass_burner Minister of Fire

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    We have both options, we're thinking of putting it on an exterior wall in the master BR; but we also have full basement with lots of headroom. I was thinking at the end of the hallway for more even distribution. I don't suppose there are models that can cool/heat and humidify.
  10. velvetfoot

    velvetfoot Minister of Fire

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    Would the cool air sink downstairs before it cooled off the master bedroom?
  11. mass_burner

    mass_burner Minister of Fire

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    downstairs? we don't have a second story.
  12. velvetfoot

    velvetfoot Minister of Fire

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    Well, then I guess it won't sink downstairs. :)
  13. mass_burner

    mass_burner Minister of Fire

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    The specs on the M-series heat pump gives the btu's, but how can I tell how big a space this will heat/cool. I'm wondering if a centrally located single unit at the end of the hallway (at the opening to two bedrooms) will heat/cool those bedrooms, hallway, and adjoining baths.

    Cooling:
    Rated Capacity 9000 Btu/h (2.64 kW) *1
    Capacity Range 2800 - 9000 BTU/h (0.8 - 2.6 kW)

    Heating at 47° F
    Rated Capacity 10900 Btu/h (3.2 kW) *2
    Capacity Range 3000 - 18000 Btu/h (0.9 - 5.3 kW)

    Heating at 17° F
    Maximum Capacity 12500 Btu/h (3.7 kW)
  14. Joful

    Joful Minister of Fire

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    Three possible ways to go at this:

    1. Heat loss calculations, based on assumed typical values (experience).
    2. IR camera and blower door test data.
    3. Experience with your existing system (how big is it? does it do the job? how many window units did it take to keep cool in July?).
  15. AK13

    AK13 Burning Hunk

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    There are no mini-splits that humidify. They DE-humidify though.
  16. mass_burner

    mass_burner Minister of Fire

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    maybe while we're getting an HP estimate we can ask about humidifying in the winter. hate waking up in the night with dry nose/mouth. i have a portable humidfier on wheels but its pretty big, a tad noisy.
  17. mass_burner

    mass_burner Minister of Fire

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    what about 15 * volume = BTU's needed
  18. AK13

    AK13 Burning Hunk

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    I've never seen that rule of thumb. Any idea what the basis is? You are basically saying 15 btu/hr/cubic foot. That is a new one to me. Is that sizing for heating or cooling?
  19. mass_burner

    mass_burner Minister of Fire

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    saw

    saw it online, can't remember where. thought it would be familiar.
  20. moey

    moey Minister of Fire

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    There is no general rule when it comes to BTU's

    slant fin has a heat loss program its pretty good http://www.pvsullivan.com/Downloads.html I dont know why they no longer have it on their website they have a android/iphone app on there but not the windows version. Keep in mind garbage in garbage out.
  21. mass_burner

    mass_burner Minister of Fire

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    okay, so here are the room sizes. all cielings 8'.
    1 BR, 12 x 12,
    1 BR, 15 x 20, including bath,
    hallway, 3 x 16
    bath, laundry, 12 x 7
    so that's 4608 cu ft.
  22. mass_burner

    mass_burner Minister of Fire

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    so I did the calulator at Mitsubishi website and this came out:

    Cooling Capacity: 11100Btu
    Heating Capacity: 13600Btu
    SEER Rating Range: 15
  23. mass_burner

    mass_burner Minister of Fire

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    estimate came in:

    option 1: 1 head unit: $5490 installed, MUZ-GE12NA / MSZ-GE12NA
    option 2: 2 head unit: $7455 installed, MXZ-GE12NA/ MSZ-GE12NA, MSZ-GE09NA
  24. peakbagger

    peakbagger Minister of Fire

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    The equipment cost is around $2300 so the rest is installation and markup for a warrantee. At that sort of markup they can buy two and have one sit on the shelf in case your original one breaks down.

    I expect a skilled crew of two could do the install in four hours if they have the right tools. It took me about 12 hours and about 2 hours to purge the lines and pump them out.
    Last edited: Jun 20, 2014
  25. AK13

    AK13 Burning Hunk

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    I think you are being a big conservative there. You don't know what all is included in that quote, how long the runs are, etc. 8 man hours seems pretty optimistic to mount both units, run refrigerant piping, power wiring, condensate piping. Could be cutting and patching for line set installation (but I doubt it). You don't know if they are putting it on a nice raised stand or dropping it on pressure treated sleepers. Plus does your $2300 include the linesets, drain piping, breakers, wiring. Plus don't forget overhead. .

    Sure, you could do it cheaper DIY, but I think its wrong to imply that the contractor is making a killing with "that sort of markup". The pricing looks about right.

    OP, your outdoor unit model number for the multizone option looks wrong.

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