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  1. #14
    Join Date
    Mar 2013
    Posts
    19
    Quote Originally Posted by RyanHughes View Post
    X2. We don't know what "total" means in this case -- was it adjusted based on SHR?

    Keith,did you tell him your typical set points in the summer/winter? You're on the right track, but you do not want to oversize 2-stage units. Low stage of a 4 ton dual stage scroll unit would cover your total load, which defeats the purpose. I would clarify why he is suggesting a 4 ton unit? A lot of times the existing ductwork isn't capable of moving the required airflow. A variable speed motor will have a greater ability to move the air against greater external pressure, but the ductwork still needs to be fixed or the system will be loud and energy inefficient. You want to make sure that the ductwork is looked over and any changes needed be made. Big difference between a 3 ton and a 4 ton system.

    What size is the existing system?
    The system is sorta mismatched I'm told. 3-ton condenser, 4-ton coil. It has an old Allstyle coil they say with one huge return duct coming into the furnace with a 16" opening I believe.

  2. #15
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,369
    I would stay with a 3 ton if it always kept you comfortable. No reason to go up in size.

  3. #16
    Join Date
    Mar 2013
    Posts
    19
    One last thing is that I am not sure if it is 32,775 or 35,775 BTU/h because my copy is a copy. There is a subtotal that clearly shows 29,890 then there is NO number that adds "Gains from Ductwork" which consists of: In Crawl Space (x 1.09) or In Attic Space (x 1.13). The total after that is either 32,775 or 35,775. It is hard to tell so I assumed 32,775 since the subtotal number was 29,890.

    Sorry again.

  4. #17
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,369
    Keith, for the ~13 years that the air conditioner ran, did the 3 ton ever fail to keep you comfortable regardless of outdoor temp?

  5. #18
    Join Date
    Mar 2013
    Posts
    19
    Quote Originally Posted by RyanHughes View Post
    Keith, for the ~13 years that the air conditioner ran, did the 3 ton ever fail to keep you comfortable regardless of outdoor temp?
    No, it has always done a great job. Will there be a big difference in cost from 3-ton to 4-ton? Now that I read that if it is struggling for air flow it could be noisy scares me.

  6. #19
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
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    3,369
    Quote Originally Posted by KeithGP View Post
    No, it has always done a great job. Will there be a big difference in cost from 3-ton to 4-ton? Now that I read that if it is struggling for air flow it could be noisy scares me.
    Then stay with a 3 ton. Going to a 4 ton two-stage system makes no sense, and cost difference should not even be a factor in this decision. You want the right size equipment because it's what you need, not bigger because the cost difference is marginal. There was recently a post very similar to this matter where the OP was being told to get a 5 ton because it didn't cost much more than a 4 ton. However, bigger doesn't perform better when paired with undersized ductwork. And many residential duct systems need work to begin with. You can spend extra for the 4 ton system you don't need and then end up with a louder system and be less comfortable as it will run short cycles in low stage and not dehumidify very well. Based on the information you've provided, a 3 ton two stage system would be appropriate.

    I think you'd be very happy with the new variable speed 2-stage system as long as it's sized and installed properly.

  7. #20
    Join Date
    Apr 2003
    Location
    Maple Grove, MN
    Posts
    1,247
    One ton=12,000 btu. Therefore, even at 35,775 btu, you are still technically oversized with a 3 ton unit. It appears that the last company out to your house did a decent load calculation. Bigger is not better. DON'T go with a 4 ton unit!

    An oversized unit will...
    -Be noisy
    -Cost more to operate.
    -De-humidify poorly
    -Cycle on and off too often
    -Operate poorly with marginal ductwork
    -Not last as long
    -Could cause uneven temperatures in different areas of the house

    Sadly, a lot of companies are afraid to offer smaller equipment to customers, and/or a lot of customers are afraid of taking a reputable company's advice to install a smaller unit, because they don't know any better.

    You do know better now.

  8. #21
    Join Date
    Mar 2013
    Posts
    19
    Quote Originally Posted by ammoniadog View Post

    You do know better now.
    This I do. I have all these 4-ton quotes. Ouch.

  9. #22
    Join Date
    Aug 2010
    Location
    West Monroe, LA
    Posts
    1,529
    Quote Originally Posted by KeithGP View Post
    This I do. I have all these 4-ton quotes. Ouch.
    Then to me I don't think you have found the right installing company. It's not uncommon to see this with your current systems set up. Outdoor unit one size and coil and furnace another. Why I couldn't tell you but ones things still stays the same if the outdoor unit is a (3) ton no matter what's inside it want deliver more then 36,000 btu's or less due to the outdoor unit compressor.

    Sure some manfactors have inside coil rating that can achive higher btu's for a system but often in air handlers being greater then the outdoor unit size that's on paper the truth is the unit since mismatched might not be delivering (3) tons of cooling? Going to a (4) ton just doesn't make sense at all.

    A proper Load cal.! Without that they are all guessing including us to what size system needs to go in. An just because the unit might be 2 stage does not make it right to oversize. So before processing with any company ask for manual j. Which it appears you have but the while the numbers make sense to us to they to the installer? If the load cal. Is accurate it is only showing the home to need a (3) ton. So why they are suggesting a (4) ton I could not tell you. As per you your existing (3) ton did a good job of cooling the home! Know if a proper matched (3) ton was installed should do even better as the system should be rated with manfactors specs. No guessing any of your contractors can access this info from their manfactor of equipment.

  10. #23
    Join Date
    Mar 2013
    Posts
    19
    The company that just came out and completed the Manual-J suggested the 4-ton because of the equipment he was gonna install. He looked at some paper and it showed the numbers supported the Amana 4-ton. More factors to consider is that as stayed above this is the upstairs unit of 2 units in the home. The downstairs unit is fine for now. It is a 4-ton unit. Also, the old units are R-22 going to R-410a. I don't know if this is any factor at all.

    I will definitely get another load cal and another evaluation of what I truly need now. I am VERY appreciative of everyone's help.

  11. #24
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,614
    they are quoting a 4 ton because there is more profit in it for them dont fall for the trap .if the 3 ton kept you comfy dont go bigger . also alot of companys use a outdoor temp in the load calc that you might see 2 or 3 times a year
    We really need change now

  12. #25
    Join Date
    Mar 2013
    Posts
    19
    I've been reading the forums on wifi thermostats for my system. Initially, I visioned going with a Nest but there are so many other factors. Some system dehumidify and variable stage

    Do companies have different options of systems they can install or will I be stuck with oned size fits all packages?

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