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  1. #1

    What size HVAC Unit for a 2,400 sf house?

    I'm installing a new condenser, coil and furnace. I have a 2,400sf home and currently have a 4 ton system in there, but have been told by the HVAC company that I should put in a 5 ton system. Is that okay?

    Also, I'm getting the total tax credit just installing the A/C, so was considering the 80% AFUE furnace, but also considering the 95% AFUE furnace. It's more $, is it worth it?

    THANK YOU!!
    Last edited by hjohnston; 07-29-2009 at 06:39 PM.

  2. #2
    Join Date
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    Quote Originally Posted by hjohnston View Post
    I'm installing a new condenser, coil and furnace. I have a 2,400sf home and currently have a 4 ton system in there, but have been told by the HVAC company that I should put in a 5 ton system. Is that okay?
    Your contractor needs to do a Manual J load calculation to determine your heat loss and heat gain figures. These indicate how large a AC and furnace you need. If your contractor hasn't done this, he's either guessing about what size AC to install or is trying to clear out whatever he can get cheap.

    Also, I'm getting the total tax credit just installing the A/C, so was considering the 80% AFUE furnace, but also considering the 95% AFUE furnace.
    Depends on your house's heat loss and length of the heating season.
    Last edited by beenthere; 07-29-2009 at 08:50 PM. Reason: Removed prices

  3. #3
    Thank you! I live in Dallas...not sure about the home's heat loss, but it can get pretty cold down here, but not for long...

  4. #4
    Join Date
    Feb 2008
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    Dallas & Longview, TX
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    Were you having problems with the 4 ton keeping up with the cooling?

    Remove pricing as per forum rules.

  5. #5
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    King Ranch Texas
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    this ones gonna be great.....

  6. #6
    Thanks - didn't now you couldn't post $$! No, the 4 ton is not having trouble keeping up.

  7. #7
    Join Date
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    If 4 ton unit was keeping up then the only thing you will do by increasing it to 5 tons is the decrease in humidity removal. The 4 ton may be perfect or maybe oversized. Run a load calculation and see before you spend the money on a new system.

    I'd go for a heat pump with a 80% furnace as backup heat. Cost a very small amount more but will save alot of expense. Also stay with a variable speed blower.

    Find a new AC company as the company that quoted your new system is already cutting corners it seems to me.

  8. #8
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    4H: Hot, Humid Houston H.O.
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    Quote Originally Posted by hjohnston View Post
    I'm installing a new condenser, coil and furnace. I have a 2,400sf home and currently have a 4 ton system in there, but have been told by the HVAC company that I should put in a 5 ton system. Is that okay?

    Also, I'm getting the total tax credit just installing the A/C, so was considering the 80% AFUE furnace, but also considering the 95% AFUE furnace. It's more $, is it worth it?

    THANK YOU!!
    Just wondering, did the AC guy say it would be OK to increase duct air speed by 25%? I have looked at ACCA Manual D and it does not seem to support that you can casually do that. If some testing was done to establish the duct system was that much over-designed, or if he proposed to change ductwork for higher capacity, that would be different.

    Assuming he did not, as a homeowner I *might* consider this yet another reason to use a pro who adheres better to ACCA methods.

    Best of luck -- Pstu

  9. #9
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    did the company tell you they would upgrade you to a 5 ton and make it cool a lot faster

  10. #10
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    Jul 2009
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    Windsor Mill, Maryland.
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    Quote Originally Posted by pstu View Post
    Just wondering, did the AC guy say it would be OK to increase duct air speed by 25%? I have looked at ACCA Manual D and it does not seem to support that you can casually do that. If some testing was done to establish the duct system was that much over-designed, or if he proposed to change ductwork for higher capacity, that would be different.

    Assuming he did not, as a homeowner I *might* consider this yet another reason to use a pro who adheres better to ACCA methods.

    Best of luck -- Pstu
    You are correct. When it come to installing a variable speed blower it's accentual that the duct work is compatible.

  11. #11
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    Quote Originally Posted by Daltex View Post
    If 4 ton unit was keeping up then the only thing you will do by increasing it to 5 tons is the decrease in humidity removal. The 4 ton may be perfect or maybe oversized. Run a load calculation and see before you spend the money on a new system.

    I'd go for a heat pump with a 80% furnace as backup heat. Cost a very small amount more but will save alot of expense. Also stay with a variable speed blower.

    Find a new AC company as the company that quoted your new system is already cutting corners it seems to me.
    Good question.

  12. #12
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    Make double sure there is a certificate to go along with that 5 Ton AC system that qualifies for the tax credit. I doubt it.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  13. #13
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    Quote Originally Posted by hjohnston View Post
    Thanks - didn't now you couldn't post $$! No, the 4 ton is not having trouble keeping up.
    The performance in conducting a manual j can be questionable. It depends on the age of the home and how tight it is, oversize is far worst than under sizing an a/c system. Conducting a manual j is effective in new construction. At lease in new construction you know all the installation factors in order to make a true calculation, that's were the use of performing a manual j is most effective.
    Last edited by Ti Llaves; 07-29-2009 at 09:33 PM. Reason: To add additional info.

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