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  1. #1
    Join Date
    Jul 2012
    Posts
    8

    New 4 ton AC heat pump system options?

    Hi All,

    We currently have a struggling 4 ton system. It used to be a 4 ton Trane XB-1000 unit that we've tried to replace with a similar 4 ton Goodman (old but unused). It runs but it can't handle cooling down the house and uses a ton of electricity. (See here.) So we are having to consider getting a new system installed.

    We are in East-Texas, which means hot and humid, so we would like to know what our best options are. We have a reputable Trane specialist in town that we are considering using for the new system.

    Our house is 2100 square feet, had wooden siding (lap and gap), both outside and inside. Inside the walls it's mostly regular R-13 insulation, but since the house is older (1978) I'm sure the walls aren't the most energy efficient walls. However, I am in the process of replacing some of the siding (wainscot) and caulking and painting the same. Also, I have the materials to put in ridge vents on the roof to add ventilation for the attic. Further, the house is on a concrete slab that stays pretty cool, considering.

    Since our house is all electric, we will have to go with a heat pump system. What we aren't sure about is what type of system would be best for our particular situation. Cost is a consideration, yes, but since we have to consider the high humidity levels of this area we were wondering if we need a 2 stage system or if a 1 stage will be fine.

    I've read quite a few posts here on the forum, and since we are considering the local Trane specialist we were interested in both the XL15i and XL20i as these appear to be favored by many here on the forum. Are these good units for our climate and home (generally speaking), or would you recommend different units?

    Also, since our old unit was old technology, we don't know if we would still need a 4 ton system for this house, or if you think a smaller tonnage would be preferable? We don't have very harsh winters here, but it can get cold enough to freeze our plumbing from time to time, so we would also like to know what type of heating strip would be a good option in relation to the rest of the system.

    We will of course have the AC guys come out and do an estimate, but we would like to have some information going into this that we might ask the AC company about (models, combinations, etc.).

    Thanks so much

  2. #2
    Join Date
    May 2012
    Location
    San Diego, CA
    Posts
    352
    I would have the AC guy do a manual J or equivalent load calculation, that way you can correctly size your unit. If the unit is correctly size, then the unit shouldn't cycle on and off and you will have better humidity control.

    A 2 stage will be better during partial loads since it is usually two compressors, but they have lower capacities and are less efficient on the really hot days.

    I am not loyal to any brand, (we generally use Carrier or York just because their reps are more helpful) but on paper they are all about the same.
    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)

  3. #3
    Join Date
    Jul 2012
    Posts
    8
    Thank you for your reply, hcong.

    I just had one AC company come out and he is going to provide me with some system options in different price and efficiency ranges.

    He got onto the attic and checked the outside unit (the Goodman unit that was to replace the XB1000) and the system was running. He was seeing how much heat it was pulling from the house and how well the unit appeared to be running otherwise and said that he'd 'almost bet' something hadn't been hooked up right, and that he thought that perhaps the heatstrip is coming on at the same time as the cooling.

    I had actually considered that when I read about this on this or another forum. The guys that hooked up the outside unit last week will come by again today and check everything, so I will definitely tell them to check for the heatstrip possibility as well.

    If we could make it another number of seasons with the current system, it would surely help us out a LOT

    But we are still considering the all-new option as well and will be getting some more estimates for that as well.

  4. #4
    Join Date
    Jul 2012
    Posts
    8
    (I posted the same post in my original thread too

    Thanks for the help, gentlemen, but we have found the issue:

    A relay on the attic unit had gone bad and some of the heatstrips were coming on (2 out of 4, or half anyway, I believe) at the same time as the cooling came on. So the AC guy fixed it and sure enough the temps coming out of the vents started getting into the 60's. On the vent closets to the attic unit I just got 63 degrees, which is about 9 degrees cooler than previously.

    The house is starting to feel cool again! Yay! Hopefully we can run this unit for some more years to come! Thanks everyone for all the help and suggestions

  5. #5
    Join Date
    May 2012
    Location
    San Diego, CA
    Posts
    352
    nice thanks for the update.
    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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