Sizing AC

[oceanblues]

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 The windows are dual pane but outdated and most likely have no gas left in them.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...

[Bazooka Joe]

Buy your own accurate heat loss heat gain calculations. One source is hvaccomputer.com minimal cost for a home owners special load calculation

[lkapigian]

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

[oceanblues]

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.

[lkapigian]

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

[vstech]

90F 80% ...1600 ft2... and spray foamed attic. ..

I'm guessing 2 ton. 2 stage or variable. ..

[oceanblues]

I put everything but square footage haha its 1750

[dan sw fl]

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

[lkapigian]

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

[teddy bear]

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

[GaryBlack]

Thanks for sharing this information.