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Thread: Help me choose HVAC system

  1. #1
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    Help me choose HVAC system

    3 story home with 3 units. Bottom floor is 2000 SF and has combo gas furnace (90% efficiency, 60,000 BTU) and 3.5 Ton Trane AC unit.

    Downstairs AC condenser is shot and needs to be replaced. 13 year old R-22 unit. Looking for replacement options. Current system quite noisy as unit is located near the one return.

    Live in Coastal SC so AC unit gets most of the work. Not sure if furnace (also 13 years old) should be replaced as it is working fine. Only planning on living here for 4 more years.

    Current pro I'm working with works with Lennox and Carrier. Not sure if I need the efficiency or cost of the Lennox model. Planning to contact the local pros on here as well.

    Any suggestions on where to start?

  2. #2
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    Question one is what is actually wrong with the condensing unit?
    If it needs a compressor then it's not worth fixing. But most other things are cheap and easy.
    A matched system is always better, but frankly I do a lot of mis matched installs and they are perfectly fine. So the new equipment will work with the old stuff.
    However you likely won't be eligible for rebates that way.
    Now carrier vs Lennox? I'd be going with the cheaper option as it's not a matched system anyway.
    And the reality is that there really is very little difference between manufacturers. They all source components from the same places anyway
    You don't squat with your spurs on.
    And you NEVER put the torches away before pressure testing.

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  4. #3
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    Quote Originally Posted by Restaurant mech View Post
    Question one is what is actually wrong with the condensing unit?
    If it needs a compressor then it's not worth fixing. But most other things are cheap and easy.
    A matched system is always better, but frankly I do a lot of mis matched installs and they are perfectly fine. So the new equipment will work with the old stuff.
    However you likely won't be eligible for rebates that way.
    Now carrier vs Lennox? I'd be going with the cheaper option as it's not a matched system anyway.
    And the reality is that there really is very little difference between manufacturers. They all source components from the same places anyway
    It's a 13 year old unit that we've been wanting to replace for a few years. Multiple calls and repairs over the last 2 years, plus we would like to get away from Freon. We have a warranty company that has bent over backwards fixing this thing. They finally threw their hands up and are going to give me some credit to replacing the unit. It would have cost me out of pocket to convert the unit to R410 anyway.

    So, will be replacing the AC unit. One installer suggested a dual fuel heat pump, but I will likely keep the furnace. Only plan on living in the house for another 5 years. The return is located not far from the unit so the fan noise is excessive downstairs, so a quiet unit is a must. Efficiency less important. However, most of the quiet units are also 2 stage or variable units raising the pricing considerably.

    Any suggestions?

  5. #4
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    Could be that the return is under sized, and causing the noise, not the furnace itself.
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  6. #5
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    Quote Originally Posted by beenthere View Post
    Could be that the return is under sized, and causing the noise, not the furnace itself.
    Maybe, but it is a large return, 20 X 25

  7. #6
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    Quote Originally Posted by ckelly14 View Post
    Maybe, but it is a large return, 20 X 25
    Okay. Is it mechanical noise, or air noise that you hear? If air noise, its too small. 20x30 would be better for 3 tons. Allows the air to move slower through the grille.

    What size is the duct going to the return.
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  8. #7
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    The intake to the AC unit is only a foot from the return and the "duct" between them is as large as the return. Hard to describe. I took a pic but could not post because I'm new here.

    I think it's the fan and not related intake restriction but I'm no expert.

    If I don't replace the furnace, am I stuck with the same blower? Is the fan considered park of the AC unit or the furnace?

  9. #8
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    Answered my own question. I guess the air handler is part of the furnace so to improve the noise would have to replace the furnace as well. Is that right?

  10. #9
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    expensive solution but:

    3 stories at least 2 systems better with 3!

  11. #10
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    Quote Originally Posted by pecmsg View Post
    expensive solution but:

    3 stories at least 2 systems better with 3!
    I do have 3 systems. See the first quote. Only the first floor system is inoperable...

  12. #11
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    When this system was working properly how did it do keeping the house cool? Did it seem to struggle or did it cycle on/off a lot?

    I don't know anything about your climate or house so don't take this as anything but a wild guess but 3 ton seems a lot for 2000 Sq Ft when you have protection from above with the other 2 systems. If it is too large that could explain in part the short life of it.

    I would want a company to do a Man J load calculation before just changing like for like.

  13. #12
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    Quote Originally Posted by BNME8EZ View Post
    When this system was working properly how did it do keeping the house cool? Did it seem to struggle or did it cycle on/off a lot?

    I don't know anything about your climate or house so don't take this as anything but a wild guess but 3 ton seems a lot for 2000 Sq Ft when you have protection from above with the other 2 systems. If it is too large that could explain in part the short life of it.

    I would want a company to do a Man J load calculation before just changing like for like.
    The evaporator is 3.5 tons and the condenser was 2.5 tons. I guess it is actually running like a 2.5 ton unit?

    Unit ran great for heating and cooling and was the best unit in the house before its demise...

  14. #13
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    Maybe a coastal unit? such as what Carrier makes, with a transferable manufacturer warranty to new owner as a selling point?

    My son in law father has a house that he purchased last year very close to the ocean in NC, and has a 3 year old outdoor unit ( indoor section original to the house ) the outdoor unit looks like it’s 30 years old, rusted panels, fins deterioration. He called for a basic PM check and the Tech. was afraid to wash the outdoor coil as the fins where deteriorating already. Guessing your not as close to the ocean if it lasted 13 years. I can see this person ( son in law father ) replacing the coil at the very least, in a few short years on his unit.

  15. #14
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    Mechanical noise then. Won't matter what furnace you have then. You'll still have some mechanical.

    Does the furnace room door face a hallway? If so, might be possible to relocate the return to that door. And then close off the current return opening. That would reduce some of the mechanical noise.
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