Correct tonnage requires a heat gain/loss calc for the structure.

I have 3 tons for 1700 square feet in Baltimore. Probably oversized by 1/2 ton but I have a heat pump in an all-electric home and need those additional btu's for winter.

2800 square ft. in NJ 4tons XL15i Trane, 100k btu XV95 furnace

Key1

1850 sq ft. Kansas City MO 3.5ton Tempstar/ICP 13 seer HP.

3.5 tons, 2500 sq. ft. + additional 800 in basement conditioned. I have shade, and it may be undersized a tad bit.

What we have to keep in mind is that these are nominal values. The delivered capacity is impacted by many things... coil condition, refrigerant charge, airflow, ductwork size, etc.

Texas runs about 21-23 BTU/sq ft.

Thats about right for your house. (22.01)

Houston here, 9 tons, 4550 sq ft (24)

For a comparision, NY & PA ran about 16-18 sq ft

Texas, near Houston.

2,550 sq. ft.

5 tons.

1500 sq. ft. in PA, using 2 tons.

Houston TX. 2850sq ft. 7 tons in 2 units (3 and 4) both 2 speed. Also 2 tons in 1100 sq ft workshop/garage space which is undersized but rarely used.

Wow JC, thats heavy on the home AC.

JC, you must have one monster electric bill ! Or maybe you don't.

I have talked with several ac techs and all use the old school calculation of 400 sq ft per ton no matter what and that burns me up.

When my builder built my house he gave me one unit (4 ton) and I really wish he had split the house and given me two.

2 is nice, I was wishing for a 3rd to handle master bed and bath only

"Houston here, 9 tons, 4550 sq ft (24)"

- Wow. I may rent a room for a weekend getaway :)
Hope you were OK thru the big hurricane.

"3.5 tons, 2500 sq. ft. + additional 800 in basement conditioned. I have shade, and it may be undersized a tad bit."

- Ryan: You will be one happy guy when you finally get the system you've been planning.

Take care.

Well, we'll see how this hacked setup gets me through this coming (quickly) winter. A/C worked fine when it was fixed. Heating mode concerns me given the lack of a TXV. I think I'm going to ride this system out. When it breaks, I'll be able to get a nice system.

With regards to sizing, I'm not sure if I'm convinced I need to go to 4 tons even though one load calc showed a little over 3.5 tons required. I don't believe it took into account the shading I have along with the additional improvements I will make down the road. 3.5 tons never really had any problems keeping the place cool, and it cycles fine. I can't base anything off my current system, though, since I don't know the ratings from the mismatch.

"A/C worked fine when it was fixed."

- I think that this is a sign that you have good air flow, decent btu's and/or adequate insulation. If not, you'd see a noticable temp differential between floors or the system wouldn't keep up at all. We also had no real summer weather after July in MD.

"With regards to sizing, I'm not sure if I'm convinced I need to go to 4 tons even though one load calc showed a little over 3.5 tons required."

- My opinion: OK to oversize by 1/2 ton if you have a heat pump as primary heat in a climate that heating is as important as cooling. You should be able to dehumidify OK since you have good air flow.

"I can't base anything off my current system, though, since I don't know the ratings from the mismatch."

- Good mystery question.

Take care.

I have a mismatched system also Ryan with no TXV and it really burns me up thinking about the small amount the builder saved that costs me every time it comes on. I thought about just adding a txv but I think I will wait and replace the whole system in a few years or try to make geothermal happen.

Does the system really benefit from the txv in heating mode?

Not being a pro, I can't answer that with certainty. I'm not sure if it would help much in heating mode. It would be nice to have instead of a fixed orifice, though. Gary, I agree and don't have a big problem oversizing 1/2 ton (in fact I believe it is approved by ACCA to do so if a heat pump is being used--I think they allow some percentage of oversizing); however, it's the air handler size that would be my concern. I have around 72 inches to work with before the supply plenum starts. That would make a 58" Trane air handler hard to fit and with only a 14" return box (which may be okay). Carrier and Rheem have shorter air handlers that work.

"I think I will wait and replace the whole system in a few years or try to make geothermal happen"

- Your electric rate has to be very high and you have to have a high-usage climate to usually justify the price of geo-thermal as a replacement system. $20k to $30k systems have a high payback time unless they're rolled into the mortgage when the house is built. If not, geo-thermal will definitely benefit the next owner of your home.

Take care.

"..it's the air handler size that would be my concern."

OK - that's your big issue and will ultimately decide on what you choose. I'm sure you'll make it work to be most efficient.

Take care.

Central Florida. 2000 sq. ft, 3.5 ton Dukane w/HRU for free hot water. Radiant barrier roof decking, 30" eaves to shade south windows, minimal west windows, east windows shaded by porch, no tree shade (hurricanes here), 10' ceilings, many ceiling fans, $135 highest electric bill in summer.

Ryan and Mo... In my old house, My AC guy suggested replacing the evaporator coil with one with a TVX. Didn't notice any measurable saving which is why I went with a cheaper Ducane system in my new house. I doubt the new place would benefit much from a TVX evaporator given the low electric usage I'm enjoying.

"- Wow. I may rent a room for a weekend getaway :)
Hope you were OK thru the big hurricane."

Thanks Gary, not even a loose shingle here
I'm west of city.
I paided extra for bracing, hurricane ties and better roof besides

When deciding on location I looked at elevations, drainage, flood plains, history, and distance from Gulf.
(Besides schools and all the normal stuff)

Loation, location, location!

My electric utility will throw in a 750.00 rebate per ton for geothermal. The utility I work for will finance up to $8,500.00 of it zero interest. I can do some if not a majority of the heat sink depending on which method if I chose to but probably would not have any warranty on that part which is a negative factor. I can also get rebates for 15+ seer HP's.. and zero interest financing.

For anyone even considering updating their system they really need to check into rebates offered by their utility.

2400sqft 2 story colonial in Connecticut. surrounded by a lot of trees. Home built 2006. just about every room has a ceiling fan.

Single zone 3 ton system by Heil. I was worried at first but it works. i put it down to 69-70 with no problems. must be a tight house.

@5000 sq' when done, 2 story 5 ton + 4 ton Trane xl19i vs air handler

Oklahoma. 4 tons downstairs (1800 sq ft) and 2.5 tons upstairs (1300 sq ft).

i'm purchasing a home in southwest florida that had the ac unit stolen. it was a 3 ton unit and i had a hvac guy tell me i needed a 4 ton unit (and therefore must also replace the 3 ton handler....an expense of 4,800$ for everything). the house is 2,000 sq ft, 15' cathedral in the living room and 10' everywhere else. can i get away with a 3 ton unit or should i go with the 4? money is tight and i would like to go with the 3 ton if i can get away with it.

ps. the house faces south, has one window on the west and 2 on the east. shading is minimal. but if i have ceiling fans in every room, will this change the size of the unit needed? thanks in advance.

J franzke,

Only way to tell is with a load calculation. Going to a 4-ton system with a 3-ton ductwork system is a very bad idea. It won't be efficient and you run the risk of not even getting the 4 tons due to the limiting ductwork system. No system performs well without the proper ductwork. Airflow-deprived systems can have shortened lifespans. Keep calling around.

2100 sqft. Baltimore, Maryland 3 Ton Rheem to be installed this weekend. Two 7.5 KW staged and of course the HW IAQ.