Mini-Split to replace 20 year old 1.5 ton Trane?
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  1. #1

    Mini-Split to replace 20 year old 1.5 ton Trane?

    Have a 24x24 room with 8' flat ceilings. R13 wall insulation, 4 skylights, 1 Anderson French Door and 1 Anderson sliding door, 4 24x48 windows, 1 48x48 window. Windows and Sliding door on exterior walls facing South West/North East. South-East wall is brick faced and an interior wall to rest of house. North-West wall is interior wall to attached insulated garage (set back 10 feet from front of 24x24 room). Room was added in 1991 (good contractors used, decent insulation for the time (R13 walls, R19 floor, R38 ceiling). Vapor barrier installed under Vinyl Siding. Room has one interior door to laundry room that leads to kitchen. House located in Central MD.

    Tile floor, drywall on all interior walls except brick wall. Southwest exterior is brick. No trees/shade. Black asphalt roof with ridge vent and soffit venting (and gable vent that was never sealed ....) Truss attic with 22"x22" access inside of a closet at edge of room.

    Current system: Trane 1.5 ton heat pump mounted in attic. 5 supply registers in ceiling with 1 return in wall with filter. System had condensor replaced about 10 years ago (Trane XE1000 replaced original XE800). Evaporator coils were not replaced. Not sure about duct-work condition (was installed 20 years ago by one of the listed/recommended contractors here).

    Currently HVAC company diagnosed the following:
    Backup electric coils non-functional (need replacing) - stopped working last year
    AH Fan relay stuck (needs replacing)

    Parts are available to service this unit....

    Challenge with replacing system (if we decide to do so):
    Unit installed before drywall installed - will need to cut large hole in drywall to replace existing unit in attic. (Not a big deal)
    Original contractor installed 1 supply to garage (Big no-no - must be removed ASAP no matter what .... CO poisioning issue ...)

    ------------------------------------------------------------------------------------------

    Options:
    1) Repair unit (system cools marginally now, heated marginally last winter) - current system was fine for 18+ years .... HVAC contractor did not test condensor yet .... just diagnosed constant fan and no backup heat problem.
    2) Replace unit with modern similar split system (would need to do some major drywall removal, not a huge issue) - manual-j would be requested (do they sell smaller than 1.5 ton??) Current HVAC contractor installed Carrier Performance system in main house, would inquire about Carrier Greenspeed for this room.
    3) Abandon current system and install mini-split in room of proper size. Might desire having ceiling-mounted system verus wall mounted system due to low ceilings and little room above windows/doors for wall-mounted system. Current HVAC contractor does not have mini-split experience and expressed concerns about even heating/cooling from one unit mounted on wall (was not aware of ceiling mount units).

    -----------------------------------------------------------------------------------------------------

    My questions to the pros:
    1) Seems a mini-split might be very effecient for a single open room of this size?
    2) Should we put money into current old system?
    3) Other ideas?

  2. #2
    Join Date
    Apr 2010
    Location
    NC Sandhills
    Posts
    384
    How often is this room used? Also how long have you notice the marginal cooling, more than one year?

  3. #3
    Quote Originally Posted by Rodney28334 View Post
    How often is this room used? Also how long have you notice the marginal cooling, more than one year?
    Room is used most days (watching TV, exercise bike) and sometimes into early evening (watching news, etc.) Typically 3-6 hours a day.

    Noticed marginal heating/cooling within the last 7 months (observed March 2012 and throughout summer). Everything seemed fine before then.

  4. #4
    Join Date
    Oct 2006
    Location
    The Beach
    Posts
    674
    That mini-split sounds like a good idea. Get a company that has installed this type of system before. They do a real good job for one room.
    Blue Fox

  5. #5
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    20,770
    While I do not live in your area now... I lived in Falls Church a few decades ago... kinda remember the climate.

    The mini will use less electricity and feel a bit better in the winter. Air circulation will be a bit of an issue in a room that large with one ceiling cassette mini... and not all companies make one head mini systems using the ceiling cassette.

    Here is a different solution that takes advantage of both worlds... albeit find a heat and AC company that has experience with it:

    http://www.daikinac.com/DOC/Consumer...20Tri-Fold.pdf

    This solution would require the ceiling surgery... however would give you more or less the performance of a mini, through the ducts.

    Again, find a dealer with experience in this brand.


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  6. #6
    Join Date
    May 2012
    Location
    San Diego, CA
    Posts
    352
    Quote Originally Posted by chloeourdog View Post
    Have a 24x24 room with 8' flat ceilings. R13 wall insulation, 4 skylights, 1 Anderson French Door and 1 Anderson sliding door, 4 24x48 windows, 1 48x48 window. Windows and Sliding door on exterior walls facing South West/North East. South-East wall is brick faced and an interior wall to rest of house. North-West wall is interior wall to attached insulated garage (set back 10 feet from front of 24x24 room). Room was added in 1991 (good contractors used, decent insulation for the time (R13 walls, R19 floor, R38 ceiling). Vapor barrier installed under Vinyl Siding. Room has one interior door to laundry room that leads to kitchen. House located in Central MD.

    Tile floor, drywall on all interior walls except brick wall. Southwest exterior is brick. No trees/shade. Black asphalt roof with ridge vent and soffit venting (and gable vent that was never sealed ....) Truss attic with 22"x22" access inside of a closet at edge of room.

    Current system: Trane 1.5 ton heat pump mounted in attic. 5 supply registers in ceiling with 1 return in wall with filter. System had condensor replaced about 10 years ago (Trane XE1000 replaced original XE800). Evaporator coils were not replaced. Not sure about duct-work condition (was installed 20 years ago by one of the listed/recommended contractors here).

    Currently HVAC company diagnosed the following:
    Backup electric coils non-functional (need replacing) - stopped working last year
    AH Fan relay stuck (needs replacing)

    Parts are available to service this unit....

    Challenge with replacing system (if we decide to do so):
    Unit installed before drywall installed - will need to cut large hole in drywall to replace existing unit in attic. (Not a big deal)
    Original contractor installed 1 supply to garage (Big no-no - must be removed ASAP no matter what .... CO poisioning issue ...)

    ------------------------------------------------------------------------------------------

    Options:
    1) Repair unit (system cools marginally now, heated marginally last winter) - current system was fine for 18+ years .... HVAC contractor did not test condensor yet .... just diagnosed constant fan and no backup heat problem.
    2) Replace unit with modern similar split system (would need to do some major drywall removal, not a huge issue) - manual-j would be requested (do they sell smaller than 1.5 ton??) Current HVAC contractor installed Carrier Performance system in main house, would inquire about Carrier Greenspeed for this room.
    3) Abandon current system and install mini-split in room of proper size. Might desire having ceiling-mounted system verus wall mounted system due to low ceilings and little room above windows/doors for wall-mounted system. Current HVAC contractor does not have mini-split experience and expressed concerns about even heating/cooling from one unit mounted on wall (was not aware of ceiling mount units).

    -----------------------------------------------------------------------------------------------------

    My questions to the pros:
    1) Seems a mini-split might be very effecient for a single open room of this size?
    2) Should we put money into current old system?
    3) Other ideas?
    1). Yes. mini-splits can get up to 21 SEER and this is a lot cheaper than what you would be paying for a similar efficiency split system. Mini-splits also get as small as 1 ton, smallest split systems are around 1.5 to 2 tons.
    2). I know some units have lasted longer, but usually it is around 15 years before major repairs. Your repairs don't seem that extensive yet, but the perk is you will be saving on your electricity bill in addition to not paying for repair cost.
    3. Ceiling mounted systems are available by all manufacturers... LG, Mitsubishi, Samsung, Fujitsu, etc... If it is only serving one room you should be fine. If you really want, the mini-splits come in multi-zone models (a lot more expensive) that allows you to split the cooling between two or more indoor units.
    You can call me Sam

    It should be a crime to be a mechanical engineer in San Diego
    Summer Design Temperature: 83 F Dry Bulb ~ 69 F Wet Bulb (California Climate Zone 7)

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