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Community and Q&A

Mount outdoor unit on the wall or on the ground?

Clay Whitenack | Posted in Green Products and Materials on

I am close to installing 3 fujitsu mini split units at our home under construction. Two outdoor units will be installed near each other, with the third installed in a different area of the house. The HVAC installer asked if I wanted to mount them on the wall or on the ground. I can’t decide which I would prefer. Any thoughts on the pros and cons of each?

I live in central KY, zone 4A. We don’t get much deep snow around here, maybe once every 10-20 years.

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Replies

  1. Stephen Sheehy | | #1

    Mine are ground mounted. The installer suggested using a ground mount eliminates any vibrations into the house and may be a bit quieter. i suspect it's not a big deal either way, but if the units are right outside a room where people are sitting or sleeping, it makes sense to isolate them. We get lots of snow, so the units are mounted on metal stands about two feet off the ground.

  2. GBA Editor
    Patrick McCombe | | #2

    Installers that I've talked to say some people are bothered by the vibration of wall-mounted units. As Stephen suggests, most complaints occur when the unit is outside a bedroom. One drawback to ground-mounted units is you need to shovel them out if the snow pack is too deep. I'm guessing that's not likely to be a concern in Kentucky.

  3. Mike M | | #3

    Patrick, Stephen,
    Do you guys know if the noise is generally transmitted through the framed structure and members or if they are mounted to concrete and still having the vibration?

  4. GBA Editor
    Patrick McCombe | | #4

    I think the concern is with framing transferring the noise and vibration. I suspect it would be less of a problem with concrete.

  5. Stephen Sheehy | | #5

    I'm not sure if it really is a problem or just a theoretical problem.
    Here in Maine, wall mounted units are attached with some sort of damping material between the unit and the wall. Still, I think some vibration or noise could get through. I've only had to shovel the snow out of the way once, but in a snowy winter, it might need more attention.
    The minisplits are really quiet anyway. If I stand near the outside unit, i can hear the whirr of the fan, but it's pretty quiet.
    The stands are sitting on 3/4" stone, not a concrete pad.

  6. Brian P | | #6

    We have a Mitsubishi MUZ-FH12NA mounted (3' above grade due to winter snow) on our back wall (2x4" double stud, 16" OC, 5" gap). It is a pretty small house (2 stories, 24x32' footprint), so there aren't any rooms that feel distant. As far as I know the unit was installed properly and it is working well.

    There is noticeable noise and vibration...the noise level and type of vibration varies with how hard the unit is working. It's not a big deal to us and we are used to it...I'm sure some people might not notice it and it might drive other people crazy.

    I would recommend ground mount as long as that doesn't seriously compromise other factors. Even though you don't have much snow, put them above grade (even just a bit) to keep ground debris out and off the damp ground. Don't put them under a roof area that sheds lots of water, like an eave.

  7. Expert Member
    Dana Dorsett | | #7

    Ground mounted it picks up more grit, weeds & fluff, and needs more frequent cleaning.

    In tight well insulated 2x6 construction the vibe factor pf a wall mount is pretty inconsequential.

    If it's going on the wall of a 2x3 framed mobile home it could be pretty annoying, but still less annoying than freezing in the cold or sweating like a horse after the races!

  8. Joe Suhrada | | #8

    I would make a platform and in your climate I would only raise them approximately one foot off the ground. I would ideally position them on a gable end perhaps near a room such as the laundry room. I would make sure my rakes are at least two feet out to keep them as clear of precip as possible. The platform I would make would consists of treated 6x6 stained to match the details of your house or in a sense of that, something close to the ground color like the mulch. I would build a four sided blocked square using the lumber, stacked double (11"high) then I would place a fiberglass pad on top of that being sure to put some rubber (like rubber roof membrane) or foam gasket material between the fiberglass and the wood. I would set your unit there. If you believe that 11" isn't enough, than add another layer and go 16.5" high. Just do this: install the lineset with just enough play so if you need to rise it even one level HIGHER going to 22" you could do it. But you aren't in Maine, you are in the Canetuck. Your snowstorms will rarely overwhelm your platform. I simply don't believe the value of adding to your wall with the unsightlyness and the RISK of vibration plus the added hassle of framing up something structural and safe, plus the siding modifications you need to make. IF the thing vibrates after mounting it in the wall, and you want to remove it from the building, now you need to refinish and/or reside that area of the house.

  9. Bill Dietze | | #9

    Clay,
    See this previous discussion here on GBA: https://www.greenbuildingadvisor.com/community/forum/mechanicals/48351/tall-minisplit-stand-snowy-climate
    For more opinions on this (and pictures!)

  10. Clay Whitenack | | #10

    Thanks for the replies.

    Thanks Bill, I searched for the topic but didn't find that thread. Must have not used the right keywords.

    I'm leaning to an elevated ground mount, if I can find one that doesn't look terrible. The risk of vibration has me scared of wall mounting. Two of them would be mounted near the mudroom, which vibration wouldn't be an issue, but the third would be on a bedroom wall. If all three were going on the mudroom wall I might consider it.

    We don't have regular snow around here, but we can get some every now and then, and freak blizzards aren't impossible. I would hate to jeopardize the heating system just because I couldn't get outside to dig out the unit. On the other hand, this is a new construction so I'm not sure how the snow is going to drift. It could be that a bad snow could drift into the area I am planning and a 2' lift still may need digging out.

  11. Expert Member
    Dana Dorsett | | #11

    Seriously, only the princess with the pea under the mattress would be aggravated by the noise levels of a mini-split wall-bracked up an any reasonably framed house.

    Last summer I slept in a room with a 2-ton Fujitsu multi-split compressor hanging on the 2x4/R13 wall less than 2 feet from my pillow.

    Could I hear it when it was spinning up in the middle of the night?

    Yes.

    Was it very loud?

    Nope.

    It was quieter than the bath fan in the bathroom down the hall, (with both the bedroom & bathroom doors closed), and that was true even when all zones were calling for AC. It was also quieter than the Fujitsu 7RLS ductless head 4 feet from my pillow running at it's lowest speed.

  12. Brian P | | #12

    If you decide to ground mount some or all of your mini-splits, here are some links I bookmarked a while ago:
    http://www.ecomfort.com/Rectorseal-CNG/p31110.html
    http://www.ecomfort.com/Rectorseal-CWGL/p31128.html

  13. Joe Suhrada | | #13

    Read my above post. It will look very nice, be very sturdy and blend into the landscape better than some metal rack.

  14. Poliana | | #14

    Hello guys,

    My builder and the architect installed 5 heat pumps on the wall of house, where is the dinning table. They make a huge vibration and a roar that makes us not to use the dining area and the kitchen area. Now, they are proposing to install them on the foundation, but I am against it as i think that the vibration is not going to go away. My preference is the install the above the ground. What is your opinion?

  15. GBA Editor
    Martin Holladay | | #15

    Poliana,
    The best approach is to install the units on a steel stand (high enough to keep the units above the snow level in deep snow years) that is mounted on a small concrete slab near your building. This is much better than mounting the units on wall brackets.

  16. Poliana | | #16

    Here is what the architect told me:

    Both the hvac contractor and integral building design independently of each other recommended attachment to the foundation.
    They are both telling me that there will not be vibration through the foundation. The major advantage of attaching to the foundation is that there is no chance of the units ever being able to move or settle independently of the house.

  17. Expert Member
    Akos | | #17

    Clay,

    I've mounted units both ways. I have found wall mount and noise is not an issue if mounted to solid masonry (brick/cmu/concrete/stone).

    I installed one in my wife's studio that is mounted to 2x4 framed wall with board/batten siding and you definitely hear when the compressor ramps up/down.

    My two cents, unless you can mount it to solid masonry, ground mount and avoid any possible sound issues.

    Akos

  18. Deleted | | #18

    Deleted

  19. L_Range | | #19

    I would question any company, contractor or architect that would recommend bolting an AC/heat-pump unit onto the side of a house, at least if the house is constructed with poured concrete or concrete block and brick. They do NOT know what they are taking about.

    Vibration is transferred directly throughout the house making the interior space unpleasant to be in whenever the unit is running. It might be okay when bolted onto a wood frame house but we are in the process of rejecting a brand new installation for this very reason.
    In our case, it needs to be isolated from the structure of the house, on a separate stand, or taken away.

    Don't put up with being conned into doing what's easiest for the installer, do it right or suffer the unpleasant consequence.

  20. Cldlhd | | #20

    As others have said you might get some vibration wall mounting them. I put mine on the ground even though we get some snow here outside Philly. However, mine are underneath the roof which overhangs that area by about 3 ft and I raised them up off the ground a decent bit by building some paver walls with a stone cap. Cost me a bit more money but I figured if they're going to be there I'd rather have them look decent.

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