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  1. #1
    Join Date
    Sep 2009
    Posts
    102

    One more question

    I'm about to sign w/contractor, however, I just had one other question I wanted answered. If you recal from my other posts, I narrowed the selection process down to 2-contractors. Both are equally reputable, however, one wants to install 3-ton system and the other wants to install 3.5-ton. I currently have a 3.5 ton system installed in my 1820 sq.ft. under air home. The contractor that wants to install the 3-ton system was the only one that actually performed a manual J calculation, the other contractor suggested the 3.5-ton system as it has served us well. Some suggest going with the guy that performed the manual J. They suggest my current 3.5 system might be oversized to begin with. From what I understand after reading some comments on this site, is that an oversized system will short cycle and increase the humidity in the home. My current system does not seem to short cycle. If anything it runs for long periods of time during the hottest part of the day. Would this mean that it is not necessarily oversized?
    I guess I'm just a little apprehensive with going with the 3-ton system and want to be sure it is the right system for my home. According to the contractor that recommends the 3-ton system, he believes it is the correct tonage for my home. I guess I should believe him, after all, he's the expert. Thanks for your advice!

  2. #2
    Join Date
    Apr 2007
    Location
    Pa,
    Posts
    106
    Go for the 3.5 ton system. With your square footage you stated, you are pretty much on the fence with the stated capacity. But then again, I don't know anything about your house, where it is located, how tight or insulated it is, exposure to the south or any passive cooling effects(big, overhead trees?). Not sure also what type of system your putting in, psc fan or ecm fan capitability?

  3. #3
    Join Date
    Dec 2005
    Posts
    70
    Maybe call the contractor that is recommeding the 3 1/2 ton and ask him if he will do a load calc as well and see if he still comes up with 3 1/2. There are probably some other companies in your area that will come out and do a load calc for a charge and would probably like to give a proposal on the work as well.

  4. #4
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    I think the one that did the load calc. is correct.In this industry,no one wants to undersize a system.

    Might want to get it in writing that the 3 ton will maiantainn XF inside,with XF ouside.

    This is what we find when we do a load calc,and it needs to be less tonnage,customer is very hesitent to downsize.

    Could be oversized ,with undersized ducts,which reduces capacity,so it runs longer.This is what we find ,in a lot of homes,here in Florida.

  5. #5
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,842
    Quote Originally Posted by clarkie View Post
    Go for the 3.5 ton system. With your square footage you stated, you are pretty much on the fence with the stated capacity. But then again, I don't know anything about your house, where it is located, how tight or insulated it is, exposure to the south or any passive cooling effects(big, overhead trees?). Not sure also what type of system your putting in, psc fan or ecm fan capitability?

    Gee Clarkie, how'd ja figure out what he needed?
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  6. #6
    Join Date
    Dec 2005
    Posts
    70

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