Results 1 to 11 of 11

Thread: Sizing AC

  1. #1
    Join Date
    Feb 2016
    Posts
    8
    Post Likes

    Sizing AC

    So I am an installer for a company in south florida. I actually just got a job with the county doing refrigeration so I put in my notice. Amongst this I just bought a house that was foreclosed. It is missing the ac, but the air handler is here and it is 4 ton. I can find anyone to do a manual j for me unless I purchase a unit and get it installed by them. I am skeptical that my home needs a 4 ton but my boss says it does. He is using the 400 into my square footage rule of thumb. I know I know but I needed a job and he paid well. I want my house done right. I have spray foam insulation in the attic so it's well insulated. The walls are wood siding and it will be redone with insulation as part of the renovation. The house does not have many windows and faces north. I have an acre and a half so no houses close to me. The windows are dual pane but outdated and most likely have no gas left in them. There is one sliding door in each room (3), there are no windows in bathrooms or in the kitchen. There is a sliding door in the dining room, and 4 glass french doors with 2 door sized windows in the living room. That is it for windows. There is a 2 foot eve around the house. The majority of the house has 8 foot ceilings with a third of them having 11 foot vaulted ceilings. From my research I'm seeing 2.5 tons maybe a 3. How far off am I? It's very humid and warm here winter is mild average of 65 summer average is 90 with maybe around 80 percent humidity, I'm in west Palm Beach. Please help me I plan on taking more classes and doing things right the county pays for my school so I will be working hard to improve my knowledge, but I don't want to screw my house up...

  2. #2
    Join Date
    Jan 2014
    Location
    New England
    Posts
    2,617
    Post Likes
    Buy your own accurate heat loss heat gain calculations. One source is hvaccomputer.com minimal cost for a home owners special load calculation

  3. #3
    Join Date
    Aug 2013
    Location
    Visalia California 93291
    Posts
    5,362
    Post Likes
    Quote Originally Posted by oceanblues View Post
    So I am an installer for a company in south florida. I actually just got a job with the county doing refrigeration so I put in my notice. Amongst this I just bought a house that was foreclosed. It is missing the ac, but the air handler is here and it is 4 ton. I can find anyone to do a manual j for me unless I purchase a unit and get it installed by them. I am skeptical that my home needs a 4 ton but my boss says it does. He is using the 400 into my square footage rule of thumb. I know I know but I needed a job and he paid well. I want my house done right. I have spray foam insulation in the attic so it's well insulated. The walls are wood siding and it will be redone with insulation as part of the renovation. The house does not have many windows and faces north. I have an acre and a half so no houses close to me. The windows are dual pane but outdated and most likely have no gas left in them. There is one sliding door in each room (3), there are no windows in bathrooms or in the kitchen. There is a sliding door in the dining room, and 4 glass french doors with 2 door sized windows in the living room. That is it for windows. There is a 2 foot eve around the house. The majority of the house has 8 foot ceilings with a third of them having 11 foot vaulted ceilings. From my research I'm seeing 2.5 tons maybe a 3. How far off am I? It's very humid and warm here winter is mild average of 65 summer average is 90 with maybe around 80 percent humidity, I'm in west Palm Beach. Please help me I plan on taking more classes and doing things right the county pays for my school so I will be working hard to improve my knowledge, but I don't want to screw my house up...
    Email is in my profile, I will do your Manual J Monday if interested
    "If you think it is expensive to hire a professional to do the job, wait until you have hired an amateur"

    Red Adair

  4. #4
    Join Date
    Feb 2016
    Posts
    8
    Post Likes
    Thanks bazooka, I'm happy to know that service is available, I had no idea will look into it. Ikapigian I am extremely grateful of any assistance you can provide I just emailed you. I would like a professionals opinion so if you can do it then I'll be extremely grateful.

  5. #5
    Join Date
    Aug 2013
    Location
    Visalia California 93291
    Posts
    5,362
    Post Likes
    Quote Originally Posted by oceanblues View Post
    Thanks bazooka, I'm happy to know that service is available, I had no idea will look into it. Ikapigian I am extremely grateful of any assistance you can provide I just emailed you. I would like a professionals opinion so if you can do it then I'll be extremely grateful.
    No problem, I emailed you what I need...I'm sure I'll have more questions Monday
    "If you think it is expensive to hire a professional to do the job, wait until you have hired an amateur"

    Red Adair

  6. #6
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    5,579
    Post Likes
    90F 80% ...1600 ft2... and spray foamed attic. ..

    I'm guessing 2 ton. 2 stage or variable. ..
    The TRUE highest cost system is the system not installed properly...

    Do you go to a boat repairman with a sinking boat, and tell him to put in a bigger motor when he tells you to fix the holes?

    I am yourmrfixit

  7. #7
    Join Date
    Feb 2016
    Posts
    8
    Post Likes
    I put everything but square footage haha its 1750

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    7,517
    Post Likes

    HEAT GAIN ESTIMATE

    Quote Originally Posted by oceanblues View Post

    So I am an installer for a company in south florida.

    Amongst this I just bought a house that was foreclosed. It is missing the ac, but the air handler is here and it is 4 ton.

    I can find anyone to do a manual j for me unless I purchase a unit and get it installed by them.
    I am skeptical that my home needs a 4 ton but my boss says it does.
    He is using the 400 into my square footage rule of thumb.
    I know but I needed a job and he paid well. I want my house done right.

    I have spray foam insulation in the attic so it's well insulated.

    The walls are wood siding and it will be redone with insulation as part of the renovation.
    The house does not have many windows and faces north.
    I have an acre and a half so no houses close to me.

    The windows are dual pane but outdated and most likely have no gas left in them.
    There is one sliding door in each room (3), there are no windows in bathrooms or in the kitchen.
    There is a sliding door in the dining room, and
    4 glass french doors with 2 door sized windows in the living room.
    That is it for windows.

    There is a 2 foot eve around the house.

    The majority of the house has 8 foot ceilings with a third of them having 11 foot vaulted ceilings.
    From my research I'm seeing 2.5 tons maybe a 3. How far off am I?

    It's very humid and warm here winter is mild average of 65 summer average is 90 with maybe around 80 percent humidity.

    I'm in West Palm Beach.


    Please help me I plan on taking more classes and doing things right the county pays for my school so I will be working hard to improve my knowledge, but I don't want to screw my house up...
    Exactly as you said, 2.5 to 3.0 tons.

    2.5 tons if you insulate walls or
    South facing windows have tinted film.

    CALCS ATTACHED
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  9. #9
    Join Date
    Aug 2013
    Location
    Visalia California 93291
    Posts
    5,362
    Post Likes
    Quote Originally Posted by dan sw fl View Post
    Exactly as you said, 2.5 to 3.0 tons.

    2.5 tons if you insulate walls or
    South facing windows have tinted film.

    CALCS ATTACHED
    You were spot on sir- I just did the Manual J..........IF he sealed the attic since the lid id foamed it would bump to a 2 with some air going to the attic--He may chime in as I told him to check with you on that in Florida..May be a No No...My area is extremely dry so it's no big deal

  10. #10
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    7,649
    Post Likes
    This type of construction is very air tight, especially during calm winds. New FL codes strongly suggest fresh air ventilation to purge indoor pollutants and renew oxygen. Most suggest a fresh air change in 4-5 hours at a minimum when occupied. Also consider that occupants add moisture at a 1-2 lbs. per hour rate. Fresh air ventilation removes or adds moisture depending on the outside dew point.
    During hot weather infiltration/ventilation and occupancy moisture is 3-5 lbs. of moisture (latent) load that your properly setup a/c will remove. Most like 75^F, 50%RH to be comfortable. During low sensible cooling loads, supplemental dehumidification is needed to maintain 50%RH. I suggest including a small 70 pint per day whole house ventilating dehumidifier as part of space conditioning system for your home.
    Many are including this as part of high quality, comfortable homes.
    This may be new thinking and look forward to your thoughts about including fresh filtered air ventilation and dehumidification in home.
    Keep us posted about your thoughts. Ultra-Aire is a sponsor of this site and more info is available at Utra-Aire.com.
    REgards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  11. #11
    Join Date
    Mar 2016
    Posts
    11
    Post Likes
    Thanks for sharing this information.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Related Forums

Plumbing Talks | Contractor MagazineThe place where Electrical professionals meet.
Comfortech 365