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  1. #1

    Comparison of heat pump systems and ductwork options

    ~2000 sq foot 1 story home in Dallas / Fort Worth, Texas area, all electric, built in 1984, all single pane storm windows, lots of large trees, shade.

    Current system is an inefficient 4 ton ac with updraft electric furnace. I'm looking to replace entire heating / ac system with new heat pump / air handler.

    Vapor barrier on two ducts in attic has been severely damaged by UV, remaining ducts have some small holes in vapor barrier. I am trying to decide whether to replace the entire duct system or to just replace the two damaged runs. I am getting varying opinions on whether an entire new duct system is worthwhile / necessary.

    Both options include new lineset with cover, new pad, new whip/disconnect, load calculation, 10 years parts and labor, 1 year free maintenance. We are assuming 4 ton system unless load calc says otherwise.

    Here are the options.

    OPTION 1

    Lennox XP16-048 Heat Pump
    Lennox CBX32MV-060 Air Handler with ECB40-15CB heat kit
    Lennox icomfort wi-fi thermostat
    5" media filter

    OPTION 2

    American Standard Platinum XM16 Heat Pump
    American Standard Platinum XV Air Handler with 20kW heat
    honeywell red link with interface ctrl board and modem
    Perfect Fit 5" media filter

    I'm looking for a comparison of these two options, pluses and minuses of each. Any specific questions I should ask? Any options regarding the equipment / thermostat I should ask about? I am confident that both contractors would do a quality install and stand behind their work.

    Any advice would be greatly appreciated!
    Last edited by RobertTX; 04-25-2013 at 01:35 PM. Reason: corrected typo in lennox AH model

  2. #2
    Join Date
    May 2007
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    DC Metro Area (MD)
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    Doubt you need 20 kW of strip heat (A/S estimate).

  3. #3
    Thanks for the input Ryan. My existing system has 20 kW, and I'm sure he estimated the same for now with plans to size properly per heat load calc.

  4. #4
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    5,520
    I'm partial, but you might also try and find a Carrier or Bryant dealer and look at a Infinity or Evolution system including pricing out their Greenspeed heat pump. In your climate it would almost never even use heat strips for heating and is around 20 SEER in 4 or 5 ton size and can slow to about 35% capacity on low stage so it would run constantly most of the time.

    Both of the option above are nice units and are fairly comparable except Trane controller isn't communicating with the equipment. Trance has their own advanced touchscreen communicating controller, but you need the communicating air handler and condenser. You could also look at the XL20i as well since your looking at premium options. I would trade wifi for a higher effciency system if needed.

  5. #5
    Thanks for the replies!

    Any advice about the ductwork? Should I replace the two bad runs or all of the ductwork?

  6. #6
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,595
    Trane 17.50 SEER, 12.50 EER, 9 HSPF

    Lennox 16.20 SEER, 12.50 EER, 8.5 HSPF

    Trane wins on efficiency anyway.

    Old ductwork likely R4.2, for a little more you can get R8 and keep heat out of the cold air.

  7. #7
    Join Date
    May 2004
    Location
    south louisiana
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    3,319
    duct work is gray? I'd guess that the worst ducts get light from gable
    end vent or some sunlight source in attic...

    as to changing the entire duct system, it depends.
    if other ducts are showing signs of splitting..then replace.
    I find the gray duct gets brittle prior to splitting open.
    if any of the other ducts need to be replaced...do it at
    same time as change out.

    make sure that mastics are used as sealant..not foil or
    duct tapes. ducts should be mastic sealed at take offs on
    supply plenum, return plenum & each plenum mastic
    sealed to the equipment.

    then seal supply boxes at attic floor.
    your return should also be sealed air tight, or
    air will bypass that new media filter.

    once ducts, plenums & returns are sealed the
    media filter will work beautifully.

    existing homes have a good amount of duct leakage,
    sealing the ducts is an excellent investment with
    a fast payback.

    ditto on R-8.

    ask them to stage the heat strips so that they operate
    independently and you don't get full 15 or 20 Kw at one time.

    and 4 tons on 2000 sq ft is a lot. with the unit you have now
    did it short cycle? to remove humidity in hot humid climates
    you need long runtimes. when unit has short cycles of operation
    in cooling mode it doesn't run long enought to remove humidity.
    the variable speed air handler will help, but if unit is oversized
    it won't help a lot.
    has a load calc been done to determine sizing?

    oh and I like the 15-17 SEER range. no complaints on that!!

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  8. #8
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
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    7,760
    Replace all ductwork, sealed with mastic and insulated with R8. That's the only way you will get close to the rated efficiencies of the equipment. Having the equipment and duct in the attic affects the capacity/efficiency greatly especially if its leaky and poorly insulated. Make sure the duct is of adequate size for the size unit the manual J calls for, the best way is to have a manual D done to design the duct system. Balancing dampers on the branch lines will allow for balancing flow to all the registers in case you end up with a room that gets to hot/cold. Hope this helps.

  9. #9
    Thanks for all the replies!

    The contractor will do a manual j to determine the right size.

    Existing ducts are grey and yes the worst one sees sunlight from a vent. If I decide not to replace all of the ductwork, he well mastic seal the return air chase, clean and seal all the register boots to the sheet rock, replace all return and supply grills, mastic seal the supply plenum, replace damaged duct runs. The cost difference to do this versus complete new ducting is big. I know my current duct insulation is not as good as r8, but if it will be 10+ years to make the money back for new ductwork I want to save the money now.

  10. #10
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
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    7,760
    Quote Originally Posted by RobertTX View Post
    Thanks for all the replies!

    The contractor will do a manual j to determine the right size.

    Existing ducts are grey and yes the worst one sees sunlight from a vent. If I decide not to replace all of the ductwork, he well mastic seal the return air chase, clean and seal all the register boots to the sheet rock, replace all return and supply grills, mastic seal the supply plenum, replace damaged duct runs. The cost difference to do this versus complete new ducting is big. I know my current duct insulation is not as good as r8, but if it will be 10+ years to make the money back for new ductwork I want to save the money now.
    Doing minor sealing and replacing of existing duct will help but won't be near as good as all new duct (sized, sealed, and insulated correctly). Older duct systems tend to be extremely leaky 25-40+% leakage.

  11. #11
    Join Date
    May 2004
    Location
    south louisiana
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    3,319
    why are you replacing suppy & return grills? are the ones you have damaged?
    when they are removed to do the mastic seal of the boot to the ceiling, run them
    thru the dishwasher to clean them.
    use the $$ saved towards replacing duct.

    as flex only leaks from either end (unless it is torn) a pretty good job can be
    done mastic sealing them. the savings between R-4 & R-8 duct often isn't worth
    the cost to replace unless there is damage to duct or something like mold inside
    of them. also the plenums should be mastic sealed to equipment.

    attached is a pic of how I seal supply boxes to sheetrock from inside the house,
    using hardcast brand #1402 mastic tape. have hvac company use this tape
    as other mastics are not as strong.

    best of luck.

    Name:  how to seal supply box from inside with MASTIC tape only.jpg
Views: 458
Size:  46.0 KB
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  12. #12
    Contractor said the throws on my supply grills are wrong for my rooms and airflow, temp consistency can be improved.

    I can't access the picture you linked to but I trust my contractor will seal the supply boxes right.

    Thanks for your input! I'm feeling better about sealing the existing ductwork and replacing only the damaged runs.

  13. #13
    Join Date
    May 2004
    Location
    south louisiana
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    you cantake the grills down & turn the grills in the opposite direction if they don't have
    adjustable fins or opposed blades on back side.
    you will be spending a pretty penny on new grills.
    that said...
    at the minimum you'd want a 3 way grill, if 4 way grills are out of
    your price range. these grills have adjustable curved blade fins to
    put the air exactly where you want it to go.
    replacing grills won't necessairly improve air flow..this comes from
    duct, but it will allow you to direct air.

    strange that you can't see the pic...one of the great things about
    this forum is that you can put the pic in the reply & not as attachment.
    I wonder why it isn't showing up for you???
    I wouln't be so trusting about properly sealing supply boxes to ceilings...
    ...seeing what I've seen over the years... methods used to seal this area
    are not providing a total seal.
    caulk doesn't work because caulk doesn't stick to sheetrock dust,
    and often gaps are larger than caulk can span. even when they
    are caulked correctly..the caulk shrinks as it dries and second
    application is needed 24 hours later.
    most caulk & put grills back up...and caulk sticks to grill
    & not gaps.
    foil tapes won't stick to both sheetrock & metal like
    mastic tape does.
    foam causes more problems by increasing the lift of the
    box off the attic floor with a seal that is not continous.

    I"ve done a lot of testing & finding out what works & doesn't
    over the years..my method seals well and lasts for a long time
    unlike foam & other methods.

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

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