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  1. #1
    Join Date
    Jun 2005
    Posts
    7
    Hi, I just had a few questions about Mini Splits I'm hoping anyone might be able to answer.

    1)All of these units seem to offer a 'dehumidify' mode, but from what I gather this mode is only a 'low fan speed' mode. Do any of these units offer a true dehumidify mode? (ie. heat the air back up to keep the temperature the same - I'm assuming a mini split with heating).

    My main requirement is for modest cooling in a basement room that hovers around 65% RH, I'd like to maintain that at 40-50% if I could.

    2)Is it possible to take a single zone outside unit and have two inside units installed on it? Of course they would have to be on the same zone and that fine. I just have two small rooms where even 9000BTU (the minimum mini split size) would be oversized for.

    Thanks!

  2. #2
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,633
    I'm no mini-split expert. But at the same time I've never heard of unit with reheat. That would mess up their efficiency ratings. To buy such a thing would result in hired goons from the EPA flying to your house in black helicopters and breaking your shins. What you're talking about would more likely be in a commercial product and cost a fair amount more.

    Mini-splits come in one, two and three zone varieties. I'm not aware of a unit that does more than three zones. Those would be cooling only systems that have one machine outside and one to three wall mounts inside. I'm not aware of a multi-zone heat pump mini-split. But I'm sure a mini-split expert will correct me if I'm wrong.

    Be prepared for sticker shock. They're pretty expensive.

  3. #3
    Join Date
    Feb 2003
    Posts
    1,996
    True. The dehumidify option usually runs at low fan speed and will cycle the fan only when the compressor is on.
    I don't think I've ever seen a mini-split eveporator less then 9K BTU. Sanyo and Mitsubishi have large multi-zone units but the individual evaps are never smaller then 9K.
    I think Sanyo has an air handler that gets mounted up between the floor joists like a mini-air handler. It has 3 4" duct take offs that can be piped to individual rooms.

    http://www.sanyo.com/industrial/HVAC...productID=1025

    [Edited by johnsp on 06-10-2005 at 09:27 AM]

  4. #4
    Join Date
    Aug 2002
    Location
    Southold.calm
    Posts
    4,857
    Sanyo or Samsung make a tri-zone 18 / 7 / 7. But if all you’re concerned with is humidity than just install 1 or 2 dehumidifier’s with a small window shaker. Basements that are primarily below grade need very little if any cooling.

  5. #5
    Join Date
    Nov 2001
    Location
    Seattle, WA
    Posts
    7,711
    Using any mini split for mainly dehumidification just won't work 98% of the time. It's better to just use a normal dehumidifier found at Sears or other places. Once the humidity is reasonable you probably will find the temperature confortable in a basement anyway and won't need mechanical cooling.

    But if you insist on mechanical cooling I would find a small window unit to use and just let it run. That would dehumidify just as well and cool a little for 1/10 the cost of a mini-split
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

  6. #6
    Join Date
    Jun 2005
    Posts
    7
    Thanks for all the feedback so far.

    DeltaT, I do agree in some sense with what your saying. However, the fact that I require some cooling, dehumidification and supplimental heating (to augment the existing hot water heating) in this room in the winter makes a mini-split very compelling. (This room is an entertainment room and does require some cooling, but not a lot)

    Also, I am unaware if there are any whisper-quiet, window dehumidifiers. Do you of any? floor space is at a premium in this room, and I dont want the racket of a traditional dehumidifier.

    I agree that a multi-zone unit is not what I want, because each zone is sized at 9000BTW or higher (excepting those Sanyo/Samsung ones, thanks for that tip). I'm wondering if a single-zone compressor can be used to drive two inside evaporators.

    Thanks!

  7. #7
    Join Date
    Jun 2005
    Posts
    7
    Most of these mini-splits do offer 'seamless' heating and cooling (ie. they will switch between heating and cooling depending on the ambient temperature).

    Could any of them cool (and dehumidify) to the point where the heating system is engaged in order to bring the room temperature back up? ie. ping-pong between cooling and heating.


  8. #8
    Join Date
    Nov 2001
    Location
    Seattle, WA
    Posts
    7,711
    Dehumidification is a side benefit of most any mechancial cooling system but not it's primary purpose. Mini-splits are prone to coil freezing that is why most of them have internal freeze controls. You can still use most any "window" unit either that is a heat pump or a small electric heater element to maintain temp. Fredrich (sp) makes some good ones.

    Some of the mini splits will have a control for "auto" temp control which will switch between heating to cooling. Mini splits are also available in multi-evap cooling/heating heat pump using one condensor and a variable speed compressor; or with electric strip heaters as a form of heat.

    They are expensive though but well worth me money.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

  9. #9
    Join Date
    Jun 2005
    Posts
    7
    DeltaT, the units with the "auto" temp control - do you know if these will work well in dehumidify mode as I mentioned? (ie. cool down below the heating threshold and then heat back up again to end up with a normal temp. but dryer room)

    It seems like a lot of 'portable air conditioners' have a true dehumidify mode (ie. they blow warm air back into the room) - why dont mini splits offer this?

  10. #10
    Join Date
    Nov 2001
    Location
    Seattle, WA
    Posts
    7,711
    Any mechanical cooling system that advertises a dehumidification mode will only let the system get away with so much in dehumidification mode, say 2 to 3 degrees below the temperature set point to keep the system from going into self-destruct.

    Mechanical cooling is not a primary dehumidifier unless the system is specifically built and set up for dehumidification, then it is not a "typical" mechanical cooling or A/C system.

    Al the portable room A/C that I know about only blow the condensor air outside of the conditioned room and do not recirculate the hot condensor air back into the same room or what would be the purpose of having an A/C?

    However, specifically build systems called dehumidifiers refrigerate the air and push the same air back through the hot condensor and back into the same room. But they are dehumidifiers, not air conditioners.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

  11. #11
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,633
    Perhaps he's talking about the portable air conditioners that roll around on casters and have a hose that discharges the hot air to a cracked window. I suppose if he discharged all or part of the hot air back into the space, and if it was the type that collected the condensate in a container then he'd have his dehumidifier.

  12. #12
    Join Date
    Jun 2005
    Posts
    7
    If you look at, for example:

    http://www.sharpusa.com/products/ModelLanding/0,1058,1525,00.html

    If you look at the manual online, pg21 it says "When operating dehumidification with container, the unit generates heat during dehumidification mode and the room temperature will rise".

    Sounds like it does indeed redirect the vented hot air back into the room. There are Pinguino models that do the same thing. So it does exist for these portable units. But they are even bigger than just a dehumidifer I'd really prefer the identical features in a mini-split. Otherwise, I will just get a small dehumidifier (I've found a small, quiet one by a company called surround air).

    Thanks!

  13. #13
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,633
    Right-O. And even if it wasn't in writing you could force the issue by leaving the discharge hose off (for some models). But for mini-splits it doesn't seem to be the case. Besides... Have you priced a mini-split? The price ain't so mini.

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