Well, this rule of thumb should work on most applications. AC units are predesigned for certain areas of the country. Doing the heat load calculation is the best way to figure out what you really need. As far as a profit margin per ton, the larger the unit doesn't mean more profit. But the price can go up for the SEER rating and what extra items you get with your system. Most contractors put more profit on the medium SEER rating. They call it, Good, Better, Best. Financing plays a big part in this also. The biggest issue coming up soon, the changing of the freon, also they want to eliminate all gas furnaces and package units. In California people pay hidden cost for gas furnaces and package units. Just for general knowledge, the manufacturer raises prices every 4 months. That's why prices have increased so much, inflation.
The takeaway here is, if you are in the market for an A/C system or soon will be, do what you can to improve the insulation and air sealing of your home first. You will then have a double benefit, where you can buy a smaller, less expensive A/C AND spend less on electricity to run it.
Never go off of Sq Ft. Use a manual J load calculation and size it properly. I install in Oklahoma and most houses require about 1 ton per 400sq ft. It's better to oversize (with supporting ductwork) using a multistage or variable system rather than under sizing and running 100% all the time. Using multi staging or variable systems will allow the system to dehumidify and cool properly. But if you are using a professional to do your install, demand a manual J load calculation and do it right!
I just had an AC system replaced here in OK. I know nothing about hvac so I called a company. But it’s 1,050 sq ft house. The old unit was a 3 ton. They replaced it and the coil. The unit is a Amana 15.3 seer which ran 4,400, the coil was 2500 the total cost of install was 9400. I think they overcharged me, but I didn’t have time to mess around attempting to get multiple quotes from different places. A lot of places won’t even offer a free quote. Seems over priced just based on what Google “experts” claim the costs should be.
How does a two story effect sizing versus a single story home? How do you properly size the system if you have separate ductwork for upstairs and downstairs, as well as two separate units?
Old school used to be 400 sq. ft. per ton - our manual j calcs normally say at least 900 sq ft per ton, and they have never been wrong. Glass and insulation are huge factors
Your helping a lot of people there is a bed thing related to the AC of a house and the alarm of what is going on not too many honesty around thank you again
thanks for your videos! yes, i am in SW FL in what you are describing as Zone 1. our home is 1961 sq. ft. and is built on a 10' plate. most of the ceilings are tray design and extend another 1 to 1.5 feet higher, so... when the HVAC company did our load plan, they had to take into consideration cubic feet of cooling along with square footage. i don't hear a lot of HVAC pros talking about cubic feet. our home faces NE, so we get morning sun. the back of the home faces SW so we get quite a bit of radiant heat in the afternoon through the rear windows and lanai area. our load plan calculated 3.5 tons, and it has been spot on! the system has the ability to pull down 20˚+ from outside temp and our humidity hovers in the 45 to 50% range. run times are long, but this keeps the humidity at bay. we are very comfortable.
yes, another disadvantage of being oversized (short cycling) is that the system does not run long enough to dehumidify. That only happens when the compressor is running.
Interesting thoughts. We discussed square footage when replacing the furnace and I had to argue with them that CUBIC ft is the proper analysis. 10 ft ceilings and sloping cathedral ceilings are becoming popular, and that means more heat for the same floor space in my house.
While the volume is relevant, the primary issue comes in at the "thermal envelope" - the point at which heat enters or leaves the home. The more airtight and well insulated the home is, the smaller the system is in general terms. There are many other factors, but the evaluation of the "thermal envelope" in all its features is critical.
@@HeatGeek1 of course yours is also part of the calculation, but when the temp drops that one degree to trigger the furnace, heating 50% more air volume 1 degree will take 50% more btu.
Warm air rises. High cathedral ceilings require ceiling fans to push the warm air back down to where the humans are. What good is a warm ceiling if the floor is freezing cold.
YES! Cubic feet is a far better analysis choice. My mother's house has a huge cathedral ceiling (well over 10 ft in the living room AND both bedrooms. The square footage is 2079. It came with a 3 ton AC unit which is already a bit undersized. Add to the cathedral ceilings that it was in the Palm Springs area of California where temperatures really soared in late spring, summer, and early fall. The AC bills were huge as the AC ran constantly and it took forever to cool the house. When it broke, we upsized it to 5 ton over the objections of the HVAC tech. The house started cooling down much more quickly and our bills dropped drastically. Our air never turned cold and clammyl. We've had it for 20 years and are having to add freon yearly. When it stops working I plan to get heat pump system for it and make sure it is also a 5 ton system. Thank you for pointing out that cubic feet is a far better choice for many homes especially those with high or very high ceilings. And yes, we have ceiling fans in all of the bedrooms and the living rooms which all have the very high cathedral ceilings. Average summer temps are 112. The 5 ton handles it without any problem. The 3 ton could not.
HVAC contractors will invariably oversize an A/C system. There's two reasons why. 1) They earn more on the sale of a larger system, and 2) they do not want to run the risk of a customer complaining it can't cool down their house fast enough.
Systems that are two big will short cycle and not dehumidify properly. Excessive starts and stops will kill a system prematurely. The sensible heat ratio, for various areas has to figure into the equation. This has to do with how much humidity the system has to deal with.
@@tonyedwards9972 I do know what I'm talking about. I've installed boilers, heat pumps, conventional A/C systems, indirect and tankless water heaters, solar systems... Try being less condescending.
Relative humidity is a very important part of the formula. A unit's sizing could be drastically different when living in Arizona, or on the Florida Gulf Coast.
@@Balticblue93 very true. You’ve got to get rid of all that latent heat before you can do much with sensible. In some areas, humidity is most of the load. Systems that are oversize will not dehumidify properly, because they are always short cycling
@@rodgraff1782 Here is Denver, our math is the opposite. We need to figure how much humidity we can actually bring in. I recently read we are more arid than Arizona. I fight for every ounce of humidity I can grab.
@@bobboscarato1313 And I think you do not have the entire story. I am an HVAC Engineer and specialize in Home Performance. Every single home / customer I deal with gets a whole-home AprilAire humidifier and filtration system with their new systems or I add them as part of their service contract. We run humidifiers all year round in the Denver 3/4 of the state of Colorado. I think I have that covered Bob. But I appreciate your input. The AprilAire 700 Automatic or 800 are not optional on my change-outs being that the healthiest air is 40%-55% humidity in a home.
I remember back when Sears sold furnaces and A/Cs there used to be a gag thing going around about how the Sears salesman sized them. Basically it was a piece of cardboard with 3 square holes cut in them. You'd stand at the curb, look through the holes and if the house fit in the smallest hole it was 2 1/2 ton, the medium hole was 3 ton and the large hole was 3 1/2 ton. You could also use it to size the furnace, 75,000 BTU, 100,000 BTU, 125,000 BTU respectively. I have a 3 ton Condenser with a 3 1/2 ton evap coil which gives you better dehumidification because with more coil area it pulls more humidity out of the air per cooling cycle.
Running a mismatched system with a 3 ton condenser on a 3.5 ton evaporator does not actually have any effect whatsoever on dehumidification, assuming you've correctly set your airflow for the tonnage. It has a slight energy efficiency benefit, as the small amount of extra surface area allows you to run a marginally higher coil temperature while still pulling the same amount of heat from the air. But at the end of the day, 3 tons of capacity is still 3 tons of capacity. Provided the airflow is set correctly, you're going to get the same amount of dehumidification out of either coil.
What you overlooked here which is most important is when the house was built. Homes today are built very tight an energy efficient. A 2000 square foot home built 30 years ago would require a 4 ton unit. A new home, same size and area will only require a 3 ton unit to work efficiently. Rule of thumb is generally 1 ton for every 500 square feet on an older home and 1 ton for every 700 square feet on a new home.
Not even close. The new house being built around Chicago are way smaller ac than 700 square feet per ton way smaller! I do manual j's and they are all different no rule of thumbs allowed!
Height of ceiling, how old and # windows , trees shade, house insulation R value. designing of duct work, your area humidity ...Many factors play a role in sizing your Ac unit.
A schedule J calculation should be done on any house before choosing a unit. Our new house has 2500sf downstairs and only needed a 3 ton unit. Located in South Alabama, with 2x6 exterior walls with a complete spray foamed envelope. Wrap around porches on threes sides. House lined up on a true East / West axis. All windows E-336 glass. Upstairs has 2080sf, fully foamed and needed a 2 ton unit.
O well. 2000 sqf old house, 2.5 ton very old ac. Now outside 96. Inside is set to 73. Yes it working little longer then usual, but my wife is cooking almost all day. I understand your chart, but why do I have to buy 3.5 if my 2.5 is plenty enough. I need humidity out.
In NH, I used to under size every central AC system I sold by half a ton for better humidity control! However, that changed after zoning came into play. Plus, variable speed condensing units also changed that belief.
Here is a quick formula to figure what size a home needs. This was passed onto me by the smartest HVAC engineer I’ve ever known. I will say this; that a heat/cool load manual J is the best method. With that said a quick guess can be figured by this simple formula. The home volume x one of these three multipliers, 2.6, 2.8 or 3.0. 2.6 multiplier is for modern well insulated homes. 2.8 for your average 80’s insulated home. 3.0 for older poorly insulated homes with single pane windows. Sounds crazy but it’s remarkably pretty accurate when compared to a load calc.
@Chris Moody, what is the units for the home volume for the that formula? For example for 11310 cubic feet what will be the heat/cool load manual J is for modern well insulated home? Thanks
We recently replaced our 30+ year old 2 ton AC unit with a 2 stage 3 ton AC for our two story 950 square foot house. When the old AC was working it's not enough to cool the upstairs so we went with 3 ton. Glad we did as it made a big difference. The house was built in 1989 but it had alot of insulation improvements over the years. It's not really about square footage but actual air volume in the home. Multiple stories also makes a difference. Wish we could afford a two zone AC system but considering it was already expensive as it is we went with 3 ton 2 stage to cover the entire house.
@@valeriegould1769 ... maybe not a whole second story, but you certainly need to add something for the extra cubic feet. Oh, and with an older home, you most likely don't have 12" of insulation against the roof. That's a killer right there.
A buddy of mine was a mechanical engineer and pilot. He got his HVAC license and used it as a side gig and between career job. He would actually run heat calculations and was surprised most HVAC tech only used the “rule of thumb”. He also found that techs would not properly size the ductwork. This is why there are hot and cold spots in homes. My house is an ice box in my room and the kids are warm because the afternoon sun is shining on their rooms.
As other stated there are so many other factors here that are not mentioned, a manual load calc is needed as a starting point. I also would argue that anyone installing a new HVAC system should only consider a variable speed unit and slightly oversizing is a good idea knowing that the system will be able to more quickly bring the home to temperature and then run at 30-50% load to maintain the setpoint. An oversize unit will also be able to keep up with the weather extremes that seem to happen with climate change.
Central FL here. New DRH build, 1 story multiple vaulted ceilings, 2800 SF and they went with a 3.5 ton, and I swear this thing is running all the time right now for A/C.
Just replaced my hvac here in Ft. Wayne, IN. 2400 sq, 2 stories, 5 bedrooms and a finished basement. Gets pretty warm in the summer. 5.5 tons. That one is too small. You need closer to 5. New build bs. Contractor grade. It’s gonna fail one day after the 10 year warranty is up. Almost guaranteed 🫤
The “flippers” of my house put a 3.5 on my 1134 sq ft home! And it’s been very inefficient. No idea why they chose to go with it. But man…it’s been a huge headache. Just had a huge leak inside of the condenser which costed over $4k to fix. Absolute absurdity. But I had gone 3 days without air at feels like temps of 111° outside and 91° inside. I couldn’t wait several more days for them to install a whole new unit.
This is a very good video. I replaced our HVAC system about 6 years ago. Our home is 1800 sq. ft. and was built in 1988 with vaulted ceilings. We live in Sacramento where temperatures often reach 106 degrees Fahrenheit. Sizing was a big issue. The old system had a 3 ton unit and it never cooled the house when temperatures were above 86 degrees at which time It would run from 1 to 7 p.m. without cycling on and off. Most of the dealers wanted to replace our AC system with a 3 ton unit. I did not want to do so. However, American Standard and Trane dealers suggested a 4 ton unit. In the end I installed a totally new system, including new ducts, with a 4 ton unit. It works like a champ. It cycles on and off until the temperatures exceed 103 degrees and it cools the house even on the hottest days. I can set the home thermostat at 72 degrees and I can achieve this temperature on the hottest days.
That’s interesting I’m in MS with a 4 ton and just shy of 1900 sqft. My unit fails to hit 70 on the thermostat once temps outdoors are above 93. I had a new unit installed and ducts re-wrapped, and it didn’t help. I’m seriously considering supplemental cooling with a ceiling cassette if it comes out cheaper than getting my ducts re-sized.
Your unit is oversized and your duct is still wrong. A 3 Ton should have been enough with proper duct. 72 degress is too low and your unit isnt runing long enough to remove the amount of moisture or mix the air so your having to set it to 72.
I'm 2/3 of the way through the video and I'm already stuck on the thought "just enough information to be dangerous" I wish life were simple but if you really want good performance and efficiency forget you ever saw this video. As far as sizing goes you need to talk to a contractor that is willing to do a detailed manual J heat load calculation. PS- equipment sizing and brand are SOME components of a more complex evaluation of the cost to the homeowner. Look for quality first then price second. Good luck everybody!
His method is technically wrong, but his chart produces the same result for my house as my meticulously done Wrightsoft. However given the cost of an HVAC system, it's so much better to do things the right way.
@@Beastphilosophy I would say his "chart" is more than technically wrong, I would say it's fundamentally wrong. Math questions deserve math answers. That chart is a fairytale. People tend to simplify things they don't understand.
I'm late to the party, but totally agree on the manual j. However, finding any contractor that wants to run one is extremely difficult. Had 5 quotes for our system, none of the contractors completed a manual j. Closest they got was a total return grill calc, with no consideration to return duct volume (four of six returns share the same duct). 2 returned the answer to go with the size that was already installed. 2 dropped the furnace size by 20%. The last one asked me how our comfort was, how the system operated, and then asked what size I wanted. Gave him the calc I had completed and he said no one does the calcs as they aren't worth the time. Went with his bid, which still up sized from the calc. Ended with a unit 40% smaller output then what was installed. System has seen temps over and under design, still cycles on the extremes. Playing it safe or padding bids with larger equipment is not necessary. The math works. It is better to leave a customer impressed in one's expertise, rather than questioning one's competency.
@@TimB- I just wanted to add my two cents Tim. I'll give you full credit for wanting to do things better. Just one bit of insider perspective from a contractor who does do manual J load calcs. I only do my detailed manual j and other engineering design work after the customer has committed to me doing the work. It's far too much time and experience that would be spent on a customer that ultimately doesn't pick you. I will also note that I've been fond of telling people that not all manual j calculations are created equal. If you did get a contractor to do a manual j before you give the go-ahead to do the job it would be a very sloppy low-end quality piece of work.
Two things, first it is the starting and stopping that wears out an a/c, longer runtime equates to longer life expectancy. Second, it's not what zone you live in, it's how the home was constructed. You wouldn't put the same size system in a home built 50 years ago as the same size home built 10 years ago. Do a load calculation on the home and size to that. By the way sir, NCI, National Comfort Institute, has excellent classes that teach just that, take one, please!
This is 100% correct. If I up sized my unit, it would short cycle and my humidity would be off the charts. 1884 under air and 3 ton unit works well in sw Florida. Home built in 1998. It will run all day in the summer when temps are above about 90 degrees.
I live in a tropical country, and have a 5-ton unit for my 800 sq. ft. living/dining/kitchen area. That is a standard installation in my condo development. Our gym, which is no larger than 1,000 sg. ft., has two units totaling 9 tons. The reason is a total lack of insulation; construction is concrete and glass.
In my thoughts, a climate like Arizona your dealing with a lot more sensible and no latent heat load. in that case I would size that system at 600 sqft per ton. In a case like Texas where you have very high latent heat and high sensible heat load I would size the system at 800 to 850 sqft/ ton. Yes you will have longer run times for the system, but you will bring the RH levels down significantly in the house. That makes for a more comfortable environment. Nobody likes a cold and damp feeling inside the house. It makes for longer run times for the system but that's why the manufactures invented higher SEER units. The Idea is to deal with the humidity first, or the latent heat load. then bring down the sensible heat load. Once you pull the humidity out of the space the temperature automatically feels colder. Here in central Canada/ the parries, we have a very low latent heat load, low humidity. We size residential A/C at 600 sqft/ton. When you move further down east to Ontario, Quebec and the Maritimes they have a very high latent and sensible heat load. In this case its in your best interest to under size these systems for longer run times to deal with the latent heat loads/ humidity first . The worst case scenario is when RH and Temperature intersect at 85 and 85, = instant black mold growing. Nobody wants the in their home. Keep the RH low and everything will be healthy in the house.
Great information. What size system do you suggest for a 2000 sq ft single story in San Antonio where average outdoor humidity is 60%. I'm replacing a 17 yo 3 ton 13 seer Trane heat pump.
Thank you for this. I live in a mobile home 43 miles north of Florida in southeast Georgia. IMO, mobile homes need 20%-33% more tonnage for cooling, maybe for heat, too. They are just not built as well, not insulated as well, & ducts are not sized properly, usually. Have a GREAT day, Neighbor!
ASHRAE has calculations for sizing. Typically on 95% of the worst extreme days the unit should run continuously. So essentially the most extreme few days of a summer the AC will run continuously in afternoon.
No, the most extreme days, if you follow the Manual J, it will not keep up. The proper sizing will have it run continuously under it's design conditions. Extreme temperatures are not design conditions.
Hey guy nice vid in southern az desert we try for 400 sq ft per ton on most older homes but gov doesnot want people to be cool they think when 114 out side we dont need to be cooler than 85
Duct design is the biggest problem. I have been in business for 30+ years. I’d say well over half the homes we have added a new system to, the existing duct work would not accommodate the size of equipment the home needs or home owner wants.
The best way is to do a heat load calculator. You have to consider the number of windows, the type of insulation, what part of the home is facing south, etc etc
The compressor’s job is to recapture the gaseous refrigerant that was released into the expansion coil. With on/off control mismatched systems will not work well. But smarter systems with controlled release and recapture will always output perform on/off control systems. In such systems there is no upper limit on the system size excluding the initial cost.
As HeatGeek below notes - the thermal envelope is what matters . . .effectively the rate of heat transfer between the inside and the outside of the house. This can be calculated using the heat transfer coefficients for the various elements of the building - walls, doors, windows, foundation and roof - the areas of these elements individual elements (ft2) x the differential temperature (deg.F) and the Heat Transfer Coefficients (btu/ft2/deg.F). The volume inside the building x the specific heat capacity of air x the differential temperature allows you to calculate how much heating or cooling the fluid requires in addition to the heat losses from the building envelope and the speed at which you want it to cool also affects the size of the unit but also the heating/cooling system cycling time.
It’s a lot more factors that play a part. A manual j should be performed. Your area elevation average temp etc. your roof , windows , doors , foundation, insulation , roof color , finish on house, Which way your house face all play a part
In ew york tri-state area the installers usually calculate 400 sq feet per ton, not 500. Plus the ceiling height, plus big windows and south side and etc.
You cannot size an AC system based on square footage alone. There are many factors such as shade on th house, roof color, crawl space vs concrete slab, amount of house insulation, size of windows, kind of windows, which direction those windows face and more factors. If someone is sizing your AC system based on square footage alone, they are doing it wrong.
I live in El Paso. My house is 1500 sqft and was built in 2006. My AC is a 1.5 Ton unit. This is the original system and "overall" the house is cooled and heated without an problems. We do have hot and cold spots. This is a single stage unit. If the website is correct I would need a 2.5 ton system. My concern is that all the ducting will have to be redone to handle the larger Ton size and to balance the system with a 2.5 ton system.
Get an hvac quote(multiple). Also, you might get away with a 2 ton, but the 2 stage type. Also make sure you have 2 returns and don't use filters that are overly dense. I use MERV 11. You could also add a ceiling return if a certain bedroom is problematic.
depends on where you live!!!!!!!!! im here in phoenix try a 3 1/2 ton on a 2000 sq ft home here!!! your going to be pulling that out the first summer.....
Please don’t do rule of thumb. Add a smart stat to add data for a working unit. It will record runtime and outside data. A year would be nice. Not all together wrong, but the variables can cause problems. Heat load is good. Still a fancy guess.
Perform an ACCA Manual J block load analysis followed by Manual S equipment selection guidance or you're simply guessing! There are SO many other factors than simply square footage and climate zone. Oversizing an AC unit is the worst thing you can do!
The problem is that most HVAC people are NOT doing the load analysis and are instead doing a square footage rule of thumb. We live in the desert in California. Our previous HVAC person insisted that upsizing to a 5 ton would result in a muggy uncomfortable home. But we already had that from the 3 ton that was struggling to keep the house cool when the temps were in the 90s. Once it hit 100 it was horrid. We insisted on the 5 ton. Our electrics that had been through the roof, dropped by about half!! The house stayed comfy even in the 100s. I've been here during the last few weeks when our temps soared to the 120s. The house has been cool and comfy during all that time. It is NEVER muggy. This tells me that the HVAC unit is right sized. Again, most HVAC people just don't seem to be doing the work when people ask if they're sure about the size. And they are not willing to swap out the unit IF they turn out to be wrong. That was the last offer I gave the HVAC person, we'd go with the 3 ton again IF he'd be willing to switch it out at his cost if he was wrong. In other words, put your money where your mouth is. I wish HVAC people would stop with the "Oh noo, it will be oversized!!" For those of us in the desert and with high ceilings, it just isn't true. Those HVAC people are costing people $$$. Please also note, for those of us living in the desert, humidity is NOT an issue. But heat is a BIG issue. So the fears of humidity issues are a bunch of malarky.
I live in Abilene, TX. Too bad you are too far away to help us with our HVAC issues. You seem to be knowledgeable and honest. I enjoy watching you videos. I've added it to my DIY Mini-Split project knowledge base.
If one is using the square feet method that is fine if one has 8 foot ceilings. However if one has 10 to 12 foot ceilings then that will require more BTU's from a unit. Because more inside cubic feet of air has to be run through the unit. Also a two story house should have two smaller home units to be efficient instead of just one. One unit for the down stairs and another for the upstairs as they are complete different zones.
After 35 yrs here In fl for the ideal sq ft is 500 ft per ton for a block home . If you have vaulted or high cielings adding 1/2 ton wouldnt hurt . A wood frame house that is raised with old windows i use 400 ft per ton . I have never had a home complain unit is not cooling properly . If you go oversized add a thermostat with humidity control
@@bobboscarato1313 I'm thankful our home came with separate units for downstairs and upstairs but it will increase costs when it comes time to replace them. The previous owner of the house had them replaced around the same time.
Yeah when I was a teen we had this big, 3,100 sq foot two story home WITH a basement! Balancing that house was a PITA!!!! But at least the equipment was sized properly (4 ton a/c with 80,000 BTU output gas furnace). The house was located in Indianapolis. Two systems would have been better though.
Sadly I am in zone 1, with a 32 sq ft house, and the builder of this tract only put in 5 ton ACs for these model houses. I have long felt it was undersized, as in the warmer months (about 4 months out of the year) my AC will often run for 2 hours straight without ever turning off just trying to hit a 77-78 degree temp setpoint. Which isnt even that low, and is higher than most people seem to set their AC to. When the unit finally does turn off, it will turn on 10 minutes later and run for another hour just trying to get 1-2 degrees down again. I guess when it finally goes out I will try and get dual 3 ton units, or maybe dual 3.5ton, since 6 ton and above is very uncommon for residential and seems to cost a fortune.
If your home is properly insulated, go UP 1/2 size. If you had a large tree that was cut down, go up one size. If your home is not insulated well, INSULATE IT FIRST, especially old leaky windows. THEN see if you need a new A/C. Remember to have attic venting checked for proper installation including soffit vents. Sizing can be difficult. Depends on window sizes and location, type of windows, attic, insulation, trees, etc. Can't simply go by a universal chart. Remember, summers are getting hotter every year. As an A/C ages, it's capacity goes down. Oh and if you have kids or cook a lot, go up one size. Kids do love to run in and out, throwing your expensive conditioned air right out the door.
This rule of thumb stuff is a good place to start. However if you are spending a large amount of money for a new system, you really need it calculated properly. Not square feet but cubic feet, all everything has a rating brick out side. Siding, double pane windows. Metal doors, wooden, pier and beam, slab foundation. There are a lot of calculations that go in to sizing a system. Even individual rooms need correct sizing for duct work. Either this man is right know before you buy! Cubic feet. You might like to run a search on manual j calculation on you tube. i seen one once on Williams Plumbing I can't recommend (not enough info.) but it did look interesting. No I do not know or work for Williams.
Retired from Carrier I’ve performed thousands of load calculations. I disagree on any method of square footage to capacity calculations it’s far more complex to size correctly. At the end of the day you want cycling to be minimum, sizing over capacity generally results in terrible humidity control, discomfort and premature equipment failure.
I’m in Jarrell Texas and my home was built in 2021 with 1600sqft. I have a 3Ton Carrier unit that seems to struggle with keeping cool in the afternoon during the summer months. Especially if we have company over 6-8 people or have the stove on. It won’t go past 78
When I purchased my new home, they had Put in 3 new units. Home size over 3K, I questioned the servicer he said 2 units would be hard for the home, house built in 2001.
I have 2 stage 5 ton units … 2 of them in 3300 sq.ft. And yes they are oversized on purpose.. they run on the low side 90 % of the time but when it is 100 degrees out in the summer, I can pull my house down from 80 to 73 in 1 hour… On peak off peak rates…
@@260k1s With 2 stage Copland compressors, normal run is 7 tons of capacity.. In live in Phoenix and my electric bill with no solar is 240 dollars at its highest.. 70 % less than a average.. your remarks demonstrate total ignorance…
I’ve got a 2,300 sq ft 2 story home I’m Arizona, built in 2007 with two AC units (upstairs and downstairs). Had one AC contractor trying to sell me two 3.5 ton units but seeing this video I’m thinking maybe they’re overselling me? Current units are 2.5 tons each and that has worked generally well. Thanks for the video!
I live in a single story home 1270sq ft with vaulted ceiling living room/ dining room . Zone2. 2 ton or 2.5 ton. Currently 2ton unit 25 years and can’t keep up when 93 degrees outside
Same in the desert in California. We upsized to a 5 ton from a 3 ton and our electric bills were almost half due to the ac not running constantly. We keep our ac at 75.
@@valeriegould1769 is your home a regular 3 bedroom 2 bathroom? Asking because I am getting a new HVAC system and initially thought a 3 ton would be sufficient, but given that the home is located in the desert, I think a 4 or 5 ton might be better.
@@DonBolas00 No, our home is not a regular 3 bedroom 2 bath. It has cathedral ceilings in two of the three bedrooms and in the living room. The cathedral ceilings go from 8 feet to 13 feet. The living room is 15' x 13' and the two bedrooms are about 14' x 13'. The high ceilings are basically the equivalent of adding a room and a half in terms of cubic feet. We also have a formal dining room as well as a breakfast area, if that helps. Given our temps in the desert are going up not down, I would get at least the 4 ton. I will not be downsizing when this a/c unit goes out. I'll keep the same size but go to a heat pump. One other item. I know some people who got a heat pump in the desert but saw the electric bills go up due to it running constantly to keep up with the heat. They were told their bills would go down. Why? In talking to an HVAC friend, the heat pump was undersized. They stuck with the same size heat pump as their HVAC which had been struggling. They thought (because they were told this) that because heat pumps were more efficient that they did not need to upsize. That was only partially true. It is handling the heat BUT it has to run constantly and that is running up the electric bills. When we switched from a 3 ton to a 5 ton our electric bills were cut in half!! So yes, I'd go to a 4 ton. If it helps, our square footage is 1385. That's square, not cubic. Good luck!
I can understand that heat load can be a factor for the difference of around 20%. I live in India and our general prescription is around 12000 BTU for 150 square feet This is for concrete buildings with moderate insulation. I still don't understand why the difference is up to three times. Can you please explain?
Odd result, IME. I’m in zone 4, 3700 total square feet and was manual J sized at, and have been living with for 25 years, a 2.5 ton system. The chart says 5 tons isn’t enough. It’s a pretty standard house - ceiling height, number of windows, number of doors, occupants, etc.
Thanks man, I gotta put a new system in zone 1 and the house is old , early - mid 50's - 1500 sq feet In Oklahoma. In My search I found a 3.5 ton. the old system is incredibly old. I mean, it is a Chrysler. LOL I am thinking it's been in that house since I was a child, it is horrendous. I have been searching and found a complete set up that I can afford, i just have to load it up a drive it to the house, incredibly far really. but the house is old asf , I do plan on upgrading some but there is not going to be much I can do but upgrade windows and insulation. I was pretty sure it would need to be over sized and I am going to go with that unit I found as the universe generally does me correct. LOL Now I just gotta find someone who knows what they are doing to help me install it.
Great video! Thanks. When considering the size of the system I was hoping you would address the volume of a room, high vaulted ceilings plus 9 foot flat ceilings increase the volume we are cooling vs 8 foot ceilings throughout.
I was hoping the same thing. I have a 3800 square foot home with several areas of vaulted ceiling that currently has 2x3-ton units that doesn't seem to cool properly during hot days.
The extra foot or so of ceiling height is factored into a proper manual j load calculation but generally speaking it's not a huge difference in the heat load. Other things like window quality orientation and shading are far more significant than ceiling height, but in truth there are so many factors I couldn't even begin to list them here. I'm sorry but I don't recommend listening to this guy. He mentions doing " a quick heat load calculation before you purchase". Quick load calcs are sloppy load calcs. Good ones take time and diligence. This is more of a sales video than anything else.
HVAC contractors dont do heat load calcs, they use this chart and call it a day. A proper one is very involved / time consuming and cuts into their profits. They are all about slapping in some overpriced equipment as quickly as possible and making several thousand profit per house.
@@Mach141 true/not true. I agree that many, even most don't do a serious manual J, but there are those that do. Clearly you haven't met me, or you wouldn't say that. I would also say, what kind of manual j are you looking for? A free one? A $300 one? A $2500 one? I only do a manual j after I have the job(with first payment) Everything else is moot to me. I won't trust someone else's work either. On pricing- people pay for what they want. Some people WANT financing, Mercedes vans, TV commercials, techs with white collared shirts with everything but the cufflinks(LOL) If that's what they want then that's what they pay for. If you don't want that, but rather honesty, technical competence, and a commitment to quality then you have to go looking for it. If you just assume that Mr White shirt will deliver those things you are likely screwing yourself.
@@HeatGeek1 I'm not in the business. When I last replaced my system (2017) I was reading online about tons and sizing, and came across this "proper" method of sizing a home, this manual J. I read over it and was really surprised at what one requires, and quickly realized that most in the business aren't going to these lengths. As a retired Aircraft Maint. tech, we dont take shortcuts. Shortcuts can cost lives. So with that mindset, I figured a proper J manual should be done on every house, by every A/C contractor. Should it not? I'm assuming following the temp. zone chart is "good enough", and thats why it is the way it is. If you actually do one, good on you! I will hire you next time. Oh wait, you want to charge me $2,500 to do one? No thanks, the chart will have to be good enough
There is no rule of thumb for hvac sizing. Period. There are way too many variables. Since the vast majority of new homes’ systems never are actually sized, every homeowner should get a Manual J when replacing their system.
Got a question for you. 10-12 years ago found a contractor I *really* like. Was very knowledgible on our situation. 2 story house.. Built in 1981. We're in the concrete jungle of DFW area and bought house in 1997. The HVAC was original from 81 with 2 units; 1 up and one down. I don't recall what tonnage each unit was, but it was not enough on top of 2 system barely functioning. The house was an investors quick flip, and basically it was indeed a pig with a lot of lipstick as we learned. After doing double pane windows and all doors replaced it didn't seem to work so hard. The insulation in each part of upper and lower floors is lacking at best. Rockwool average 3 inch. Masonry siding from bottom of 2nd floor up. Downstairs brick up to ceiling+ a little.. No insulation on attic walls nor any radiant barrier on roof. Upstairs is around 1400 Sq Ft and downstairs is around 1750 sq ft. Contractor suggested a 2.5 ton upstairs and wanted us to do a 3.5 ton downstairs, both single stage systems. For just a little more we went with a 16 SEER 4 ton 2 speed down stairs, which has been perfect match. Downstairs rarely kicks into high stage and can hardly even tell it's on. The upstairs 14 SEER 2.5 ton single stage does the job really well, but it does run quite a bit more during the warm to hot days. These units were installed in 2008 and have for the most part been trouble free. The 4 ton burnt up a compressor about 5 years ago, so he recommended we drop down to 3.5 ton single stage. I really didn't want to do that as we _love the quietness_ of the 2 stage system. So we opted for the 4 Ton 2 stage. Indoor humidity on the really hot days both up and down run in low 40% range during AC season. Over past few years, a new coil and outdoor unit goes thru CAPs ever couple of years.. Thus we are at a crossroads again, as to what to do. _Wondering why he seems insistent on dropping down to a 3.5 ton?_ Cant underdstand the push.. I know the #'s dont line up and a 3 ton would probably be the proper unit, but it does not come in a 2 stage compressor. IDEAS, SUGGESTIONS?
I'd get a second and third opinion. I'd also ask the contractor you like why he thinks downsizing would help. It does not seem logical to me. Upsizing does seem logical since normally things burn out when they are chronically overworked. Please let us know what happens. Oh, one other item. I'd google "Why do I have to keep replacing the coil and CAP on my ac". Googling has often found the answer for me quickly.
This is why almost every single AC system is so severely undersized. I followed these recommendations once and ended up with a system so badly undersized that it couldn’t keep the temperature at 60 degrees on a 95 degree day. The temperature would rise up towards 70 degrees with the damn unit running 24/7. Ended up running window units on top of the central unit just to keep the damn house at 55 degrees. You can’t oversize an AC. I have a 10 ton unit on my tugboat and it works awesome. It will freeze you right out of the boat if you want it to. I’ve been able to pull that boat down to 45 degrees on a 100 degree day!
@@CarreraTrackOntheFloor So your going to suffer from the heat in your house to make your AC system last longer? No thanks 60 degrees is as hot as I’m willing to suffer, 55 is nice. I’d you size your ac system correctly it will be able to keep your house at 55 degrees without running non stop. You can throw these numbers right out. A 2,000 square foot house needs a minimum of a 10 ton unit, and that’s up north. I’m willing to bet you will need 15 tons or more down south.
Interesting to look at this rule of thumb, as I bought an older house with a recently replaced HVAC system that was sold to the prior owner. SW Oklahoma, so in the northern part of Zone 1 on that chart. 1969 build, ~1200sq/ft, concrete slab foundation with wood frame construction. Mostly updated to double pane windows, though a couple older aluminum single pane ones. The system installed is a 3.5 ton system, which makes me wonder just why the system was chosen, as it's apparently a full ton oversized for the application. Profit margins? It doesn't run all that much of the time, often only a few hours a day during the middle of the summer.
All right let me ask you this I have garage about the size of a 2 car, it’s really more like a one and a half. I have a 1 1/2 ton unit all new install also insulation all been put in at the same time of the install. It won’t get below 78 runs all day long never shuts off even at night sounds undersize to me but it’s less than 800 ft.², does not have a garage door. I turned it into a workshop.
I'm in zone 4. My home is 2360 sf, built in 1940 and minimally insulated attic and only two rooms have wall insulation. I have an 8.5 SEER, 2 ton A/C. It works great on even the hottest days. Due to its small size it does a great job of dehumidifying. Running mostly without short cycling is the key to a long lasting system and to dehumidifying. It has never needed repair and the only maintenance ever has been one time i used a soft brush to clean the outside of the outside cooling fins from cottonwood fluff. My highest ever actual monthly electric bill has been $62. The house has little shade and the attic is poorly ventilated since there are no soffits on most of the house. Sadly, the author doesnt know what he's saying with his size recommendations.
This is my recommendation. Only hire a HVAC contractor that does a manual J8 heat load calculation. There’s a lot of good videos on heat load calculation on TH-cam.
I have a 1000 square foot house with a 2 ton heat pump. It keeps up up to 90 degrees then above 90 degrees then runs almost all the time. 14 year old house post and beam construction. So 2 1/2 or 3 ton when it fails
A couple of points: The irony of an "undersized" air conditioner is that they tend to run forever. They run long cycles and love it. This tends to yield more even cooling, better humidity control and they run quieter. I maintain that there is no such thing as an "undersized" air conditioner without some additional information. The "problem" with an undersized unit is that on the hottest part of the afternoon on the hottest days of the year, it might have trouble reaching the set-point. How many hours out of the year is that? Is it worth having an oversized unit and all the problems that come with it 99% of the year so that you can pull it down to 72 at 5 pm on July 4th? If a user is one of those people like to set their t-stat to 68 degrees and expect it to get there when entertaining guests at 5:00 p.m. on the hottest day--might need a four ton. In the same sized house, a user might indicate that they never set their t-stat below 80 and don't even turn it on until June would be better suited with a two ton. Same house. Four ton is right for one customer, two ton is right for the other. Square footage is rarely a factor. Load is determined by the heat gain through the walls, ceilings and floors and by considering the overall tightness of the home. At best, square footage is a number *general* contractors might use in the early budget process, but a proper load calculation should be done at some point.
@@andrewdille9796 Where do you live? If your temps don't hit a 100F very often, that might not be a big deal. But for those of us living in areas where the temps have risen to daily average of 106F to 112F with nights rarely getting below 95F a two-ton or even a three-ton just doesn't do it.
@@valeriegould1769 Hello Valerie, I live in Minnesota so at night time it usually drops to 70’F. However during the day high 90’s and sometimes 100’F plus but not often. we have terrible humidity issuers. It is really important to have the air conditioner running long periods of time to get the humidity down in the house. I had a larger air conditioner before and it would cycle a lot. It would get cold very fast and not have enough time during the cycle to remove the humidity. I am very happy with my reduce size aircondtioner.
@@andrewdille9796 Thank you for answering!! Yes, that would make a huge difference. Mom's house was 2079 sqft with huge cathedral ceilings in three large rooms. The three ton that came with the house just could not handle the heat in the late spring, summer, and fall of Palm Springs. It ran constantly and our electric bills were outrageous. Fortunately, it was not our main home. We fought with the HVAC guy to upsize it to a 5 ton when the 3 ton died. The 5 ton quickly cooled the house down and almost halved our ac bills. So besides cubic feet instead of sqft, it looks like one needs to consider where you live. Oy!
DIY'ers typically dont care about RH and calculations. They just want heat or cool. I live in PNW and biggest issue I run into is ducting is incorrect and not so much units over or under sized.
Never "estimate" A/C tonnage requirements! Always use a proper load evaluation! Also never trust a salesman. It's actually 'legal' to sell a 3 Ton unit that produces only 33,000BTUs. To reiterate the importance of load calculations, we have numerous homes in DFW with 2200-2400 sq.ft cooled by 27,000 BTUs just fine.
I'm in the process of getting central air. I had 3 quotes and each one proposed a different unit size: 2, 2.5 and 3 ton. It looks to me they are pushing their stock instead following my needs.
i got a system size for the house like explain in this video, when it was 104 outside the system will continue to run and will not drop the indoor temp below. 80. had company come out that installed it, would say the system performing as it should. it was under sized when in USE but on paper it was correct size.
Well, this rule of thumb should work on most applications. AC units are predesigned for certain areas of the country. Doing the heat load calculation is the best way to figure out what you really need. As far as a profit margin per ton, the larger the unit doesn't mean more profit. But the price can go up for the SEER rating and what extra items you get with your system. Most contractors put more profit on the medium SEER rating. They call it, Good, Better, Best. Financing plays a big part in this also. The biggest issue coming up soon, the changing of the freon, also they want to eliminate all gas furnaces and package units. In California people pay hidden cost for gas furnaces and package units. Just for general knowledge, the manufacturer raises prices every 4 months. That's why prices have increased so much, inflation.
IDK this installer, but I am impressed with the candid openness. If I lived in that area, I would buy from this vendor.
The takeaway here is, if you are in the market for an A/C system or soon will be, do what you can to improve the insulation and air sealing of your home first. You will then have a double benefit, where you can buy a smaller, less expensive A/C AND spend less on electricity to run it.
Never go off of Sq Ft. Use a manual J load calculation and size it properly. I install in Oklahoma and most houses require about 1 ton per 400sq ft. It's better to oversize (with supporting ductwork) using a multistage or variable system rather than under sizing and running 100% all the time. Using multi staging or variable systems will allow the system to dehumidify and cool properly. But if you are using a professional to do your install, demand a manual J load calculation and do it right!
Yes yes yes 😊
I just had an AC system replaced here in OK. I know nothing about hvac so I called a company.
But it’s 1,050 sq ft house. The old unit was a 3 ton. They replaced it and the coil. The unit is a Amana 15.3 seer which ran 4,400, the coil was 2500 the total cost of install was 9400. I think they overcharged me, but I didn’t have time to mess around attempting to get multiple quotes from different places. A lot of places won’t even offer a free quote.
Seems over priced just based on what Google “experts” claim the costs should be.
How does a two story effect sizing versus a single story home? How do you properly size the system if you have separate ductwork for upstairs and downstairs, as well as two separate units?
@@witzviewer do a manual j calculation with 2 zones on separate systems. Also this is where multistage and variable systems really help out as well.
Old school used to be 400 sq. ft. per ton - our manual j calcs normally say at least 900 sq ft per ton, and they have never been wrong. Glass and insulation are huge factors
Your helping a lot of people there is a bed thing related to the AC of a house and the alarm of what is going on not too many honesty around thank you again
thanks for your videos! yes, i am in SW FL in what you are describing as Zone 1. our home is 1961 sq. ft. and is built on a 10' plate. most of the ceilings are tray design and extend another 1 to 1.5 feet higher, so... when the HVAC company did our load plan, they had to take into consideration cubic feet of cooling along with square footage. i don't hear a lot of HVAC pros talking about cubic feet. our home faces NE, so we get morning sun. the back of the home faces SW so we get quite a bit of radiant heat in the afternoon through the rear windows and lanai area. our load plan calculated 3.5 tons, and it has been spot on! the system has the ability to pull down 20˚+ from outside temp and our humidity hovers in the 45 to 50% range. run times are long, but this keeps the humidity at bay. we are very comfortable.
yes, another disadvantage of being oversized (short cycling) is that the system does not run long enough to dehumidify.
That only happens when the compressor is running.
In the caribbean we use a rule of thumb of 300 sf to 350 sf per tone and that is for residencial. Now proper insulation makes a difference of course.
Interesting thoughts. We discussed square footage when replacing the furnace and I had to argue with them that CUBIC ft is the proper analysis. 10 ft ceilings and sloping cathedral ceilings are becoming popular, and that means more heat for the same floor space in my house.
While the volume is relevant, the primary issue comes in at the "thermal envelope" - the point at which heat enters or leaves the home. The more airtight and well insulated the home is, the smaller the system is in general terms. There are many other factors, but the evaluation of the "thermal envelope" in all its features is critical.
@@HeatGeek1 of course yours is also part of the calculation, but when the temp drops that one degree to trigger the furnace, heating 50% more air volume 1 degree will take 50% more btu.
@@rtel123 sorry, I don't understand what you're trying to express.
Warm air rises. High cathedral ceilings require ceiling fans to push the warm air back down to where the humans are. What good is a warm ceiling if the floor is freezing cold.
YES! Cubic feet is a far better analysis choice. My mother's house has a huge cathedral ceiling (well over 10 ft in the living room AND both bedrooms. The square footage is 2079. It came with a 3 ton AC unit which is already a bit undersized. Add to the cathedral ceilings that it was in the Palm Springs area of California where temperatures really soared in late spring, summer, and early fall. The AC bills were huge as the AC ran constantly and it took forever to cool the house. When it broke, we upsized it to 5 ton over the objections of the HVAC tech. The house started cooling down much more quickly and our bills dropped drastically. Our air never turned cold and clammyl. We've had it for 20 years and are having to add freon yearly. When it stops working I plan to get heat pump system for it and make sure it is also a 5 ton system. Thank you for pointing out that cubic feet is a far better choice for many homes especially those with high or very high ceilings. And yes, we have ceiling fans in all of the bedrooms and the living rooms which all have the very high cathedral ceilings. Average summer temps are 112. The 5 ton handles it without any problem. The 3 ton could not.
HVAC contractors will invariably oversize an A/C system. There's two reasons why. 1) They earn more on the sale of a larger system, and 2) they do not want to run the risk of a customer complaining it can't cool down their house fast enough.
Systems that are two big will short cycle and not dehumidify properly. Excessive starts and stops will kill a system prematurely. The sensible heat ratio, for various areas has to figure into the equation. This has to do with how much humidity the system has to deal with.
Thanks for saying " I don't know what I'm talking about, but heard it somewhere "
@@tonyedwards9972 I do know what I'm talking about. I've installed boilers, heat pumps, conventional A/C systems, indirect and tankless water heaters, solar systems... Try being less condescending.
@@MsAjax409 the main reason people oversize or undersized is lack of knowledge...no need for your resume, I don't hire women
@@tonyedwards9972 You're saying that there are HVAC contractors that lack the knowledge needed to do their trade?
Relative humidity is a very important part of the formula. A unit's sizing could be drastically different when living in Arizona, or on the Florida Gulf Coast.
100% agree with this comment. RH is huge in factors and latent numbers in your math.
@@Balticblue93 very true. You’ve got to get rid of all that latent heat before you can do much with sensible. In some areas, humidity is most of the load. Systems that are oversize will not dehumidify properly, because they are always short cycling
@@rodgraff1782 Here is Denver, our math is the opposite. We need to figure how much humidity we can actually bring in. I recently read we are more arid than Arizona. I fight for every ounce of humidity I can grab.
@@Balticblue93 You may want to consider a whole house humidifier!
@@bobboscarato1313 And I think you do not have the entire story. I am an HVAC Engineer and specialize in Home Performance. Every single home / customer I deal with gets a whole-home AprilAire humidifier and filtration system with their new systems or I add them as part of their service contract. We run humidifiers all year round in the Denver 3/4 of the state of Colorado. I think I have that covered Bob. But I appreciate your input. The AprilAire 700 Automatic or 800 are not optional on my change-outs being that the healthiest air is 40%-55% humidity in a home.
I remember back when Sears sold furnaces and A/Cs there used to be a gag thing going around about how the Sears salesman sized them. Basically it was a piece of cardboard with 3 square holes cut in them. You'd stand at the curb, look through the holes and if the house fit in the smallest hole it was 2 1/2 ton, the medium hole was 3 ton and the large hole was 3 1/2 ton. You could also use it to size the furnace, 75,000 BTU, 100,000 BTU, 125,000 BTU respectively.
I have a 3 ton Condenser with a 3 1/2 ton evap coil which gives you better dehumidification because with more coil area it pulls more humidity out of the air per cooling cycle.
Running a mismatched system with a 3 ton condenser on a 3.5 ton evaporator does not actually have any effect whatsoever on dehumidification, assuming you've correctly set your airflow for the tonnage. It has a slight energy efficiency benefit, as the small amount of extra surface area allows you to run a marginally higher coil temperature while still pulling the same amount of heat from the air.
But at the end of the day, 3 tons of capacity is still 3 tons of capacity. Provided the airflow is set correctly, you're going to get the same amount of dehumidification out of either coil.
LOVE the inclusion of a manual J (or heat load calculation)! Size your units properly and your house will thank you
So will your checkbook
What you overlooked here which is most important is when the house was built. Homes today are built very tight an energy efficient. A 2000 square foot home built 30 years ago would require a 4 ton unit. A new home, same size and area will only require a 3 ton unit to work efficiently. Rule of thumb is generally 1 ton for every 500 square feet on an older home and 1 ton for every 700 square feet on a new home.
I will use a 3 1/2 ton unit; no less!
Not even close. The new house being built around Chicago are way smaller ac than 700 square feet per ton way smaller! I do manual j's and they are all different no rule of thumbs allowed!
You didn't watch the video did you?
Height of ceiling, how old and # windows , trees shade, house insulation R value. designing of duct work, your area humidity ...Many factors play a role in sizing your Ac unit.
A schedule J calculation should be done on any house before choosing a unit. Our new house has 2500sf downstairs and only needed a 3 ton unit. Located in South Alabama, with 2x6 exterior walls with a complete spray foamed envelope. Wrap around porches on threes sides. House lined up on a true East / West axis. All windows E-336 glass. Upstairs has 2080sf, fully foamed and needed a 2 ton unit.
Manual J or manual N but yes
That's the right way to do it.
O well. 2000 sqf old house, 2.5 ton very old ac. Now outside 96. Inside is set to 73. Yes it working little longer then usual, but my wife is cooking almost all day. I understand your chart, but why do I have to buy 3.5 if my 2.5 is plenty enough. I need humidity out.
In NH, I used to under size every central AC system I sold by half a ton for better humidity control! However, that changed after zoning came into play. Plus, variable speed condensing units also changed that belief.
Here is a quick formula to figure what size a home needs. This was passed onto me by the smartest HVAC engineer I’ve ever known. I will say this; that a heat/cool load manual J is the best method. With that said a quick guess can be figured by this simple formula. The home volume x one of these three multipliers, 2.6, 2.8 or 3.0. 2.6 multiplier is for modern well insulated homes. 2.8 for your average 80’s insulated home. 3.0 for older poorly insulated homes with single pane windows. Sounds crazy but it’s remarkably pretty accurate when compared to a load calc.
@Chris Moody, what is the units for the home volume for the that formula? For example for 11310 cubic feet what will be the heat/cool load manual J is for modern well insulated home? Thanks
What's missing here. I have 39,000. What next?
@@nram1dived by 12,000
@@Clamjammer Thanks. I need 3.5 ton
What about widows and the direction they face? Ceiling height roof color and covering type and most importantly, where the house is located.
We recently replaced our 30+ year old 2 ton AC unit with a 2 stage 3 ton AC for our two story 950 square foot house. When the old AC was working it's not enough to cool the upstairs so we went with 3 ton. Glad we did as it made a big difference. The house was built in 1989 but it had alot of insulation improvements over the years. It's not really about square footage but actual air volume in the home. Multiple stories also makes a difference. Wish we could afford a two zone AC system but considering it was already expensive as it is we went with 3 ton 2 stage to cover the entire house.
Don't forget cathedral ceilings count as another story.
@@valeriegould1769 ... maybe not a whole second story, but you certainly need to add something for the extra cubic feet. Oh, and with an older home, you most likely don't have 12" of insulation against the roof. That's a killer right there.
Thankfully you got two stage. Had you not, you would be dealing with humidity issues especially if you live in a humid area.
A buddy of mine was a mechanical engineer and pilot. He got his HVAC license and used it as a side gig and between career job. He would actually run heat calculations and was surprised most HVAC tech only used the “rule of thumb”. He also found that techs would not properly size the ductwork. This is why there are hot and cold spots in homes. My house is an ice box in my room and the kids are warm because the afternoon sun is shining on their rooms.
As other stated there are so many other factors here that are not mentioned, a manual load calc is needed as a starting point. I also would argue that anyone installing a new HVAC system should only consider a variable speed unit and slightly oversizing is a good idea knowing that the system will be able to more quickly bring the home to temperature and then run at 30-50% load to maintain the setpoint. An oversize unit will also be able to keep up with the weather extremes that seem to happen with climate change.
Central FL here. New DRH build, 1 story multiple vaulted ceilings, 2800 SF and they went with a 3.5 ton, and I swear this thing is running all the time right now for A/C.
Just replaced my hvac here in Ft. Wayne, IN. 2400 sq, 2 stories, 5 bedrooms and a finished basement. Gets pretty warm in the summer. 5.5 tons. That one is too small. You need closer to 5. New build bs. Contractor grade. It’s gonna fail one day after the 10 year warranty is up. Almost guaranteed 🫤
It should run all the time. What temp are you keeping? central FL I wouldnt run cooler then 75
@@tekjunkie28 75
The “flippers” of my house put a 3.5 on my 1134 sq ft home! And it’s been very inefficient. No idea why they chose to go with it. But man…it’s been a huge headache. Just had a huge leak inside of the condenser which costed over $4k to fix. Absolute absurdity. But I had gone 3 days without air at feels like temps of 111° outside and 91° inside. I couldn’t wait several more days for them to install a whole new unit.
This is a very good video. I replaced our HVAC system about 6 years ago. Our home is 1800 sq. ft. and was built in 1988 with vaulted ceilings. We live in Sacramento where temperatures often reach 106 degrees Fahrenheit. Sizing was a big issue. The old system had a 3 ton unit and it never cooled the house when temperatures were above 86 degrees at which time It would run from 1 to 7 p.m. without cycling on and off. Most of the dealers wanted to replace our AC system with a 3 ton unit. I did not want to do so. However, American Standard and Trane dealers suggested a 4 ton unit. In the end I installed a totally new system, including new ducts, with a 4 ton unit. It works like a champ. It cycles on and off until the temperatures exceed 103 degrees and it cools the house even on the hottest days. I can set the home thermostat at 72 degrees and I can achieve this temperature on the hottest days.
That’s interesting I’m in MS with a 4 ton and just shy of 1900 sqft. My unit fails to hit 70 on the thermostat once temps outdoors are above 93. I had a new unit installed and ducts re-wrapped, and it didn’t help. I’m seriously considering supplemental cooling with a ceiling cassette if it comes out cheaper than getting my ducts re-sized.
@@zeroturn7091in Nevada it hits 102 outside vaulted ceilings and 1550sq ft a 5 ton struggles to be lower than 87 inside 😂 (its from 2006)
Your unit is oversized and your duct is still wrong. A 3 Ton should have been enough with proper duct. 72 degress is too low and your unit isnt runing long enough to remove the amount of moisture or mix the air so your having to set it to 72.
@@zeroturn7091 70 is too low.
@@Steve.._. You need more air flow.
Shade from trees also plays into it
What about shade from Marijuana bushes?
@@nostradamus7648 LOL
I'm 2/3 of the way through the video and I'm already stuck on the thought "just enough information to be dangerous" I wish life were simple but if you really want good performance and efficiency forget you ever saw this video. As far as sizing goes you need to talk to a contractor that is willing to do a detailed manual J heat load calculation. PS- equipment sizing and brand are SOME components of a more complex evaluation of the cost to the homeowner. Look for quality first then price second. Good luck everybody!
Most accurate comment.
His method is technically wrong, but his chart produces the same result for my house as my meticulously done Wrightsoft. However given the cost of an HVAC system, it's so much better to do things the right way.
@@Beastphilosophy I would say his "chart" is more than technically wrong, I would say it's fundamentally wrong. Math questions deserve math answers. That chart is a fairytale. People tend to simplify things they don't understand.
I'm late to the party, but totally agree on the manual j. However, finding any contractor that wants to run one is extremely difficult.
Had 5 quotes for our system, none of the contractors completed a manual j. Closest they got was a total return grill calc, with no consideration to return duct volume (four of six returns share the same duct). 2 returned the answer to go with the size that was already installed. 2 dropped the furnace size by 20%. The last one asked me how our comfort was, how the system operated, and then asked what size I wanted. Gave him the calc I had completed and he said no one does the calcs as they aren't worth the time.
Went with his bid, which still up sized from the calc. Ended with a unit 40% smaller output then what was installed. System has seen temps over and under design, still cycles on the extremes.
Playing it safe or padding bids with larger equipment is not necessary. The math works. It is better to leave a customer impressed in one's expertise, rather than questioning one's competency.
@@TimB- I just wanted to add my two cents Tim. I'll give you full credit for wanting to do things better. Just one bit of insider perspective from a contractor who does do manual J load calcs. I only do my detailed manual j and other engineering design work after the customer has committed to me doing the work. It's far too much time and experience that would be spent on a customer that ultimately doesn't pick you. I will also note that I've been fond of telling people that not all manual j calculations are created equal. If you did get a contractor to do a manual j before you give the go-ahead to do the job it would be a very sloppy low-end quality piece of work.
Two things, first it is the starting and stopping that wears out an a/c, longer runtime equates to longer life expectancy. Second, it's not what zone you live in, it's how the home was constructed. You wouldn't put the same size system in a home built 50 years ago as the same size home built 10 years ago. Do a load calculation on the home and size to that. By the way sir, NCI, National Comfort Institute, has excellent classes that teach just that, take one, please!
This is 100% correct. If I up sized my unit, it would short cycle and my humidity would be off the charts. 1884 under air and 3 ton unit works well in sw Florida. Home built in 1998. It will run all day in the summer when temps are above about 90 degrees.
I live in a tropical country, and have a 5-ton unit for my 800 sq. ft. living/dining/kitchen area. That is a standard installation in my condo development. Our gym, which is no larger than 1,000 sg. ft., has two units totaling 9 tons. The reason is a total lack of insulation; construction is concrete and glass.
Could you please do a video on selecting the correct size AC units with split system install for both larger one story and two story homes
In my thoughts, a climate like Arizona your dealing with a lot more sensible and no latent heat load. in that case I would size that system at 600 sqft per ton. In a case like Texas where you have very high latent heat and high sensible heat load I would size the system at 800 to 850 sqft/ ton. Yes you will have longer run times for the system, but you will bring the RH levels down significantly in the house. That makes for a more comfortable environment. Nobody likes a cold and damp feeling inside the house. It makes for longer run times for the system but that's why the manufactures invented higher SEER units. The Idea is to deal with the humidity first, or the latent heat load. then bring down the sensible heat load. Once you pull the humidity out of the space the temperature automatically feels colder. Here in central Canada/ the parries, we have a very low latent heat load, low humidity. We size residential A/C at 600 sqft/ton. When you move further down east to Ontario, Quebec and the Maritimes they have a very high latent and sensible heat load. In this case its in your best interest to under size these systems for longer run times to deal with the latent heat loads/ humidity first . The worst case scenario is when RH and Temperature intersect at 85 and 85, = instant black mold growing. Nobody wants the in their home. Keep the RH low and everything will be healthy in the house.
Great information. What size system do you suggest for a 2000 sq ft single story in San Antonio where average outdoor humidity is 60%.
I'm replacing a 17 yo 3 ton 13 seer Trane heat pump.
Thank you for this.
I live in a mobile home 43 miles north of Florida in southeast Georgia.
IMO, mobile homes need 20%-33% more tonnage for cooling, maybe for heat, too.
They are just not built as well, not insulated as well, & ducts are not sized properly, usually.
Have a GREAT day, Neighbor!
They have more exterior surface area than a more square shaped house.
Zennihome. The new pre-fab homes are pretty good.
ASHRAE has calculations for sizing. Typically on 95% of the worst extreme days the unit should run continuously. So essentially the most extreme few days of a summer the AC will run continuously in afternoon.
No, the most extreme days, if you follow the Manual J, it will not keep up. The proper sizing will have it run continuously under it's design conditions. Extreme temperatures are not design conditions.
also depends on current duct sizing and if you want to stick with current supply/return ducting or spend big money to up the size
There is only one reason to up size or down size duct work. You only change when it is calculated wrong in the first place.
Hey guy nice vid in southern az desert we try for 400 sq ft per ton on most older homes but gov doesnot want people to be cool they think when 114 out side we dont need to be cooler than 85
Thanks for the video and the chance to get a rough idea how big a unit a house needs.
Duct design is the biggest problem. I have been in business for 30+ years. I’d say well over half the homes we have added a new system to, the existing duct work would not accommodate the size of equipment the home needs or home owner wants.
The best way is to do a heat load calculator. You have to consider the number of windows, the type of insulation, what part of the home is facing south, etc etc
SEER rating does save money, I did it in my own home is I would know for sure.
Its volume !! Im surprised you didnt mention variable of ceiling height
The compressor’s job is to recapture the gaseous refrigerant that was released into the expansion coil. With on/off control mismatched systems will not work well. But smarter systems with controlled release and recapture will always output perform on/off control systems. In such systems there is no upper limit on the system size excluding the initial cost.
HVAC tech here. Most companies in my area size their equipment wrong.
As HeatGeek below notes - the thermal envelope is what matters . . .effectively the rate of heat transfer between the inside and the outside of the house. This can be calculated using the heat transfer coefficients for the various elements of the building - walls, doors, windows, foundation and roof - the areas of these elements individual elements (ft2) x the differential temperature (deg.F) and the Heat Transfer Coefficients (btu/ft2/deg.F). The volume inside the building x the specific heat capacity of air x the differential temperature allows you to calculate how much heating or cooling the fluid requires in addition to the heat losses from the building envelope and the speed at which you want it to cool also affects the size of the unit but also the heating/cooling system cycling time.
Yes, or a Manual J which includes ALL relevant variables.
It’s a lot more factors that play a part. A manual j should be performed. Your area elevation average temp etc. your roof , windows , doors , foundation, insulation , roof color , finish on house, Which way your house face all play a part
In ew york tri-state area the installers usually calculate 400 sq feet per ton, not 500. Plus the ceiling height, plus big windows and south side and etc.
You cannot size an AC system based on square footage alone. There are many factors such as shade on th house, roof color, crawl space vs concrete slab, amount of house insulation, size of windows, kind of windows, which direction those windows face and more factors. If someone is sizing your AC system based on square footage alone, they are doing it wrong.
Houston here and it is hot af!! my 2nd floor AC runs about 13 hours a day!!!! I have a 2 ton AC…
I live in El Paso. My house is 1500 sqft and was built in 2006. My AC is a 1.5 Ton unit. This is the original system and "overall" the house is cooled and heated without an problems. We do have hot and cold spots. This is a single stage unit. If the website is correct I would need a 2.5 ton system. My concern is that all the ducting will have to be redone to handle the larger Ton size and to balance the system with a 2.5 ton system.
Get an hvac quote(multiple). Also, you might get away with a 2 ton, but the 2 stage type. Also make sure you have 2 returns and don't use filters that are overly dense. I use MERV 11. You could also add a ceiling return if a certain bedroom is problematic.
Square feet and cubic feet are 2 different animals.. Newer homes have taller ceilings.. makes a difference..
depends on where you live!!!!!!!!! im here in phoenix try a 3 1/2 ton on a 2000 sq ft home here!!! your going to be pulling that out the first summer.....
Please don’t do rule of thumb.
Add a smart stat to add data for a working unit. It will record runtime and outside data.
A year would be nice.
Not all together wrong, but the variables can cause problems.
Heat load is good. Still a fancy guess.
Perform an ACCA Manual J block load analysis followed by Manual S equipment selection guidance or you're simply guessing!
There are SO many other factors than simply square footage and climate zone.
Oversizing an AC unit is the worst thing you can do!
The problem is that most HVAC people are NOT doing the load analysis and are instead doing a square footage rule of thumb. We live in the desert in California. Our previous HVAC person insisted that upsizing to a 5 ton would result in a muggy uncomfortable home. But we already had that from the 3 ton that was struggling to keep the house cool when the temps were in the 90s. Once it hit 100 it was horrid. We insisted on the 5 ton. Our electrics that had been through the roof, dropped by about half!! The house stayed comfy even in the 100s. I've been here during the last few weeks when our temps soared to the 120s. The house has been cool and comfy during all that time. It is NEVER muggy. This tells me that the HVAC unit is right sized. Again, most HVAC people just don't seem to be doing the work when people ask if they're sure about the size. And they are not willing to swap out the unit IF they turn out to be wrong. That was the last offer I gave the HVAC person, we'd go with the 3 ton again IF he'd be willing to switch it out at his cost if he was wrong. In other words, put your money where your mouth is. I wish HVAC people would stop with the "Oh noo, it will be oversized!!" For those of us in the desert and with high ceilings, it just isn't true. Those HVAC people are costing people $$$. Please also note, for those of us living in the desert, humidity is NOT an issue. But heat is a BIG issue. So the fears of humidity issues are a bunch of malarky.
I really like those two pictures hanging behind him.
I live in Abilene, TX. Too bad you are too far away to help us with our HVAC issues. You seem to be knowledgeable and honest. I enjoy watching you videos. I've added it to my DIY Mini-Split project knowledge base.
If one is using the square feet method that is fine if one has 8 foot ceilings. However if one has 10 to 12 foot ceilings then that will require more BTU's from a unit. Because more inside cubic feet of air has to be run through the unit. Also a two story house should have two smaller home units to be efficient instead of just one. One unit for the down stairs and another for the upstairs as they are complete different zones.
After 35 yrs here In fl for the ideal sq ft is 500 ft per ton for a block home . If you have vaulted or high cielings adding 1/2 ton wouldnt hurt . A wood frame house that is raised with old windows i use 400 ft per ton . I have never had a home complain unit is not cooling properly . If you go oversized add a thermostat with humidity control
Two story homes present a different problem in regard to size also
Two separate units is optimal for a two story home.
@@BrianNC81 True. If you live there for a long time, is worth the extra cost!
@@bobboscarato1313 I'm thankful our home came with separate units for downstairs and upstairs but it will increase costs when it comes time to replace them. The previous owner of the house had them replaced around the same time.
Yeah when I was a teen we had this big, 3,100 sq foot two story home WITH a basement! Balancing that house was a PITA!!!! But at least the equipment was sized properly (4 ton a/c with 80,000 BTU output gas furnace). The house was located in Indianapolis.
Two systems would have been better though.
Sadly I am in zone 1, with a 32 sq ft house, and the builder of this tract only put in 5 ton ACs for these model houses. I have long felt it was undersized, as in the warmer months (about 4 months out of the year) my AC will often run for 2 hours straight without ever turning off just trying to hit a 77-78 degree temp setpoint. Which isnt even that low, and is higher than most people seem to set their AC to. When the unit finally does turn off, it will turn on 10 minutes later and run for another hour just trying to get 1-2 degrees down again.
I guess when it finally goes out I will try and get dual 3 ton units, or maybe dual 3.5ton, since 6 ton and above is very uncommon for residential and seems to cost a fortune.
If your home is properly insulated, go UP 1/2 size. If you had a large tree that was cut down, go up one size.
If your home is not insulated well, INSULATE IT FIRST, especially old leaky windows. THEN see if you need a new A/C.
Remember to have attic venting checked for proper installation including soffit vents.
Sizing can be difficult. Depends on window sizes and location, type of windows, attic, insulation, trees, etc.
Can't simply go by a universal chart.
Remember, summers are getting hotter every year.
As an A/C ages, it's capacity goes down.
Oh and if you have kids or cook a lot, go up one size. Kids do love to run in and out, throwing your expensive conditioned air right out the door.
This rule of thumb stuff is a good place to start. However if you are spending a large amount of money for a new system, you really need it calculated properly. Not square feet but cubic feet, all everything has a rating brick out side. Siding, double pane windows. Metal doors, wooden, pier and beam, slab foundation. There are a lot of calculations that go in to sizing a system. Even individual rooms need correct sizing for duct work. Either this man is right know before you buy! Cubic feet. You might like to run a search on manual j calculation on you tube. i seen one once on Williams Plumbing I can't recommend (not enough info.) but it did look interesting. No I do not know or work for Williams.
Retired from Carrier I’ve performed thousands of load calculations. I disagree on any method of square footage to capacity calculations it’s far more complex to size correctly. At the end of the day you want cycling to be minimum, sizing over capacity generally results in terrible humidity control, discomfort and premature equipment failure.
I’m in Jarrell Texas and my home was built in 2021 with 1600sqft. I have a 3Ton Carrier unit that seems to struggle with keeping cool in the afternoon during the summer months. Especially if we have company over 6-8 people or have the stove on. It won’t go past 78
I would of went with 4 ton. 1 Ton for every 400 sq ft. Thats what I was taught in A/C school in Phoenic, AZ.
When I purchased my new home, they had Put in 3 new units. Home size over 3K, I questioned the servicer he said 2 units would be hard for the home, house built in 2001.
I have 2 stage 5 ton units … 2 of them in 3300 sq.ft. And yes they are oversized on purpose.. they run on the low side 90 % of the time but when it is 100 degrees out in the summer, I can pull my house down from 80 to 73 in 1 hour… On peak off peak rates…
The electric company will eat your lunch and dinner!
Electric company loves you big time. That's absurd to have 10 tons of cooling in 3300sq feet. Fuck efficiency right? 😂
@@260k1s With 2 stage Copland compressors, normal run is 7 tons of capacity.. In live in Phoenix and my electric bill with no solar is 240 dollars at its highest.. 70 % less than a average.. your remarks demonstrate total ignorance…
@@gtrguyinaz what's your cost per kwh?
@@260k1s 9 cents and other info… I have 12 foot ceilings
I’ve got a 2,300 sq ft 2 story home I’m Arizona, built in 2007 with two AC units (upstairs and downstairs). Had one AC contractor trying to sell me two 3.5 ton units but seeing this video I’m thinking maybe they’re overselling me? Current units are 2.5 tons each and that has worked generally well. Thanks for the video!
Midland, it's too hot too long. "Refrigerated air" is a must.
Without Manual J calculation?
Based off this video I think I need a 4 ton vs the current 3.5 ton.
Central Florida home built in 2007, two-story, 2260 sqft.
in the south, when you figure out the size, then double it for the humidity
I live in a single story home 1270sq ft with vaulted ceiling living room/ dining room . Zone2. 2 ton or 2.5 ton. Currently 2ton unit 25 years and can’t keep up when 93 degrees outside
I have a DRH home with a 2.5 ton unit on a 2.083 square foot. The funny thing is all the house have a 2.5 ton even the smaller homes.
In Texas go one size higher. My ac unit barely breaks a sweat. And cut my ac bill in half.
Same in the desert in California. We upsized to a 5 ton from a 3 ton and our electric bills were almost half due to the ac not running constantly. We keep our ac at 75.
@@valeriegould1769 is your home a regular 3 bedroom 2 bathroom? Asking because I am getting a new HVAC system and initially thought a 3 ton would be sufficient, but given that the home is located in the desert, I think a 4 or 5 ton might be better.
@@DonBolas00 No, our home is not a regular 3 bedroom 2 bath. It has cathedral ceilings in two of the three bedrooms and in the living room. The cathedral ceilings go from 8 feet to 13 feet. The living room is 15' x 13' and the two bedrooms are about 14' x 13'. The high ceilings are basically the equivalent of adding a room and a half in terms of cubic feet. We also have a formal dining room as well as a breakfast area, if that helps. Given our temps in the desert are going up not down, I would get at least the 4 ton. I will not be downsizing when this a/c unit goes out. I'll keep the same size but go to a heat pump. One other item. I know some people who got a heat pump in the desert but saw the electric bills go up due to it running constantly to keep up with the heat. They were told their bills would go down. Why? In talking to an HVAC friend, the heat pump was undersized. They stuck with the same size heat pump as their HVAC which had been struggling. They thought (because they were told this) that because heat pumps were more efficient that they did not need to upsize. That was only partially true. It is handling the heat BUT it has to run constantly and that is running up the electric bills. When we switched from a 3 ton to a 5 ton our electric bills were cut in half!! So yes, I'd go to a 4 ton. If it helps, our square footage is 1385. That's square, not cubic. Good luck!
@@valeriegould1769 helps a ton, pun intended, thanks you for all the information.
@@DonBolas00 My pleasure!!
I can understand that heat load can be a factor for the difference of around 20%.
I live in India and our general prescription is around 12000 BTU for 150 square feet
This is for concrete buildings with moderate insulation.
I still don't understand why the difference is up to three times.
Can you please explain?
Odd result, IME. I’m in zone 4, 3700 total square feet and was manual J sized at, and have been living with for 25 years, a 2.5 ton system. The chart says 5 tons isn’t enough. It’s a pretty standard house - ceiling height, number of windows, number of doors, occupants, etc.
We have 7 tons counting attached garage in a 1400 square foot home, upgrading to 8 this year.
7 tpns for 1400sf?? That is way oversized! I hope this is a typo.
@@annaqsmith Nope, keeps us cool.
please talk about cubic feet of air conditioned space along with square footage. tall ceilings can make a big difference in load plan.
Thanks man, I gotta put a new system in zone 1 and the house is old , early - mid 50's - 1500 sq feet In Oklahoma. In My search I found a 3.5 ton. the old system is incredibly old. I mean, it is a Chrysler. LOL I am thinking it's been in that house since I was a child, it is horrendous. I have been searching and found a complete set up that I can afford, i just have to load it up a drive it to the house, incredibly far really. but the house is old asf , I do plan on upgrading some but there is not going to be much I can do but upgrade windows and insulation. I was pretty sure it would need to be over sized and I am going to go with that unit I found as the universe generally does me correct. LOL Now I just gotta find someone who knows what they are doing to help me install it.
Short answer for ppls in Texas, 3 tons is up to 1600 sqft, 4 tons is up to 2000 sqft, 5 tons is up to 2,500 sqft
I live in San Antonio with a 2300 sf house and they gave me a 2.5 ton system. My house feels like it never cools.
Yes that seems way undersized
I'm done with central air. Midea u shaped. 2 are cooling my whole house. They shut on and off. It is awesome.
of all the HVAC companies that have recommended and or did my replacement heat load n ever came up
Great video! Thanks. When considering the size of the system I was hoping you would address the volume of a room, high vaulted ceilings plus 9 foot flat ceilings increase the volume we are cooling vs 8 foot ceilings throughout.
I was hoping the same thing. I have a 3800 square foot home with several areas of vaulted ceiling that currently has 2x3-ton units that doesn't seem to cool properly during hot days.
The extra foot or so of ceiling height is factored into a proper manual j load calculation but generally speaking it's not a huge difference in the heat load. Other things like window quality orientation and shading are far more significant than ceiling height, but in truth there are so many factors I couldn't even begin to list them here. I'm sorry but I don't recommend listening to this guy. He mentions doing " a quick heat load calculation before you purchase". Quick load calcs are sloppy load calcs. Good ones take time and diligence. This is more of a sales video than anything else.
HVAC contractors dont do heat load calcs, they use this chart and call it a day. A proper one is very involved / time consuming and cuts into their profits. They are all about slapping in some overpriced equipment as quickly as possible and making several thousand profit per house.
@@Mach141 true/not true. I agree that many, even most don't do a serious manual J, but there are those that do. Clearly you haven't met me, or you wouldn't say that. I would also say, what kind of manual j are you looking for? A free one? A $300 one? A $2500 one? I only do a manual j after I have the job(with first payment) Everything else is moot to me. I won't trust someone else's work either. On pricing- people pay for what they want. Some people WANT financing, Mercedes vans, TV commercials, techs with white collared shirts with everything but the cufflinks(LOL) If that's what they want then that's what they pay for. If you don't want that, but rather honesty, technical competence, and a commitment to quality then you have to go looking for it. If you just assume that Mr White shirt will deliver those things you are likely screwing yourself.
@@HeatGeek1 I'm not in the business. When I last replaced my system (2017) I was reading online about tons and sizing, and came across this "proper" method of sizing a home, this manual J. I read over it and was really surprised at what one requires, and quickly realized that most in the business aren't going to these lengths. As a retired Aircraft Maint. tech, we dont take shortcuts. Shortcuts can cost lives. So with that mindset, I figured a proper J manual should be done on every house, by every A/C contractor. Should it not? I'm assuming following the temp. zone chart is "good enough", and thats why it is the way it is. If you actually do one, good on you! I will hire you next time. Oh wait, you want to charge me $2,500 to do one? No thanks, the chart will have to be good enough
There is no rule of thumb for hvac sizing. Period. There are way too many variables.
Since the vast majority of new homes’ systems never are actually sized, every homeowner should get a Manual J when replacing their system.
better to have more rather than not having enough, especially when it comes to air conditioning and heating your home.
Got a question for you. 10-12 years ago found a contractor I *really* like. Was very knowledgible on our situation. 2 story house.. Built in 1981. We're in the concrete jungle of DFW area and bought house in 1997. The HVAC was original from 81 with 2 units; 1 up and one down. I don't recall what tonnage each unit was, but it was not enough on top of 2 system barely functioning. The house was an investors quick flip, and basically it was indeed a pig with a lot of lipstick as we learned. After doing double pane windows and all doors replaced it didn't seem to work so hard. The insulation in each part of upper and lower floors is lacking at best. Rockwool average 3 inch. Masonry siding from bottom of 2nd floor up. Downstairs brick up to ceiling+ a little.. No insulation on attic walls nor any radiant barrier on roof. Upstairs is around 1400 Sq Ft and downstairs is around 1750 sq ft. Contractor suggested a 2.5 ton upstairs and wanted us to do a 3.5 ton downstairs, both single stage systems. For just a little more we went with a 16 SEER 4 ton 2 speed down stairs, which has been perfect match. Downstairs rarely kicks into high stage and can hardly even tell it's on. The upstairs 14 SEER 2.5 ton single stage does the job really well, but it does run quite a bit more during the warm to hot days.
These units were installed in 2008 and have for the most part been trouble free. The 4 ton burnt up a compressor about 5 years ago, so he recommended we drop down to 3.5 ton single stage. I really didn't want to do that as we _love the quietness_ of the 2 stage system. So we opted for the 4 Ton 2 stage. Indoor humidity on the really hot days both up and down run in low 40% range during AC season. Over past few years, a new coil and outdoor unit goes thru CAPs ever couple of years.. Thus we are at a crossroads again, as to what to do. _Wondering why he seems insistent on dropping down to a 3.5 ton?_ Cant underdstand the push.. I know the #'s dont line up and a 3 ton would probably be the proper unit, but it does not come in a 2 stage compressor. IDEAS, SUGGESTIONS?
I'd get a second and third opinion. I'd also ask the contractor you like why he thinks downsizing would help. It does not seem logical to me. Upsizing does seem logical since normally things burn out when they are chronically overworked. Please let us know what happens.
Oh, one other item. I'd google "Why do I have to keep replacing the coil and CAP on my ac". Googling has often found the answer for me quickly.
This is why almost every single AC system is so severely undersized. I followed these recommendations once and ended up with a system so badly undersized that it couldn’t keep the temperature at 60 degrees on a 95 degree day. The temperature would rise up towards 70 degrees with the damn unit running 24/7. Ended up running window units on top of the central unit just to keep the damn house at 55 degrees. You can’t oversize an AC. I have a 10 ton unit on my tugboat and it works awesome. It will freeze you right out of the boat if you want it to. I’ve been able to pull that boat down to 45 degrees on a 100 degree day!
60 degrees is way too low, you're going to cause early failure in your a/c unit.
@@CarreraTrackOntheFloor So your going to suffer from the heat in your house to make your AC system last longer? No thanks 60 degrees is as hot as I’m willing to suffer, 55 is nice. I’d you size your ac system correctly it will be able to keep your house at 55 degrees without running non stop. You can throw these numbers right out. A 2,000 square foot house needs a minimum of a 10 ton unit, and that’s up north. I’m willing to bet you will need 15 tons or more down south.
@@Trump985 10 ton? lol oh ok
If I were going to upsize any component it would be the evaporator coil.
Interesting to look at this rule of thumb, as I bought an older house with a recently replaced HVAC system that was sold to the prior owner.
SW Oklahoma, so in the northern part of Zone 1 on that chart.
1969 build, ~1200sq/ft, concrete slab foundation with wood frame construction. Mostly updated to double pane windows, though a couple older aluminum single pane ones.
The system installed is a 3.5 ton system, which makes me wonder just why the system was chosen, as it's apparently a full ton oversized for the application. Profit margins? It doesn't run all that much of the time, often only a few hours a day during the middle of the summer.
Yep definitely oversized.
All right let me ask you this I have garage about the size of a 2 car, it’s really more like a one and a half. I have a 1 1/2 ton unit all new install also insulation all been put in at the same time of the install. It won’t get below 78 runs all day long never shuts off even at night sounds undersize to me but it’s less than 800 ft.², does not have a garage door. I turned it into a workshop.
I'm in zone 4. My home is 2360 sf, built in 1940 and minimally insulated attic and only two rooms have wall insulation. I have an 8.5 SEER, 2 ton A/C. It works great on even the hottest days. Due to its small size it does a great job of dehumidifying. Running mostly without short cycling is the key to a long lasting system and to dehumidifying. It has never needed repair and the only maintenance ever has been one time i used a soft brush to clean the outside of the outside cooling fins from cottonwood fluff. My highest ever actual monthly electric bill has been $62. The house has little shade and the attic is poorly ventilated since there are no soffits on most of the house. Sadly, the author doesnt know what he's saying with his size recommendations.
IDK for my area and my house he's spot on
This is my recommendation. Only hire a HVAC contractor that does a manual J8 heat load calculation. There’s a lot of good videos on heat load calculation on TH-cam.
I have a 1000 square foot house with a 2 ton heat pump. It keeps up up to 90 degrees then above 90 degrees then runs almost all the time. 14 year old house post and beam construction. So 2 1/2 or 3 ton when it fails
A couple of points:
The irony of an "undersized" air conditioner is that they tend to run forever. They run long cycles and love it. This tends to yield more even cooling, better humidity control and they run quieter.
I maintain that there is no such thing as an "undersized" air conditioner without some additional information.
The "problem" with an undersized unit is that on the hottest part of the afternoon on the hottest days of the year, it might have trouble reaching the set-point. How many hours out of the year is that? Is it worth having an oversized unit and all the problems that come with it 99% of the year so that you can pull it down to 72 at 5 pm on July 4th?
If a user is one of those people like to set their t-stat to 68 degrees and expect it to get there when entertaining guests at 5:00 p.m. on the hottest day--might need a four ton.
In the same sized house, a user might indicate that they never set their t-stat below 80 and don't even turn it on until June would be better suited with a two ton.
Same house. Four ton is right for one customer, two ton is right for the other.
Square footage is rarely a factor. Load is determined by the heat gain through the walls, ceilings and floors and by considering the overall tightness of the home.
At best, square footage is a number *general* contractors might use in the early budget process, but a proper load calculation should be done at some point.
My house is 1800 sq ft and I have a two ton. I feel it is perfectly sized. It does on the hottest day of the year (100F) run continuously.
@@andrewdille9796 Where do you live? If your temps don't hit a 100F very often, that might not be a big deal. But for those of us living in areas where the temps have risen to daily average of 106F to 112F with nights rarely getting below 95F a two-ton or even a three-ton just doesn't do it.
@@valeriegould1769 Hello Valerie, I live in Minnesota so at night time it usually drops to 70’F. However during the day high 90’s and sometimes 100’F plus but not often. we have terrible humidity issuers. It is really important to have the air conditioner running long periods of time to get the humidity down in the house. I had a larger air conditioner before and it would cycle a lot. It would get cold very fast and not have enough time during the cycle to remove the humidity. I am very happy with my reduce size aircondtioner.
@@andrewdille9796 Thank you for answering!! Yes, that would make a huge difference. Mom's house was 2079 sqft with huge cathedral ceilings in three large rooms. The three ton that came with the house just could not handle the heat in the late spring, summer, and fall of Palm Springs. It ran constantly and our electric bills were outrageous. Fortunately, it was not our main home. We fought with the HVAC guy to upsize it to a 5 ton when the 3 ton died. The 5 ton quickly cooled the house down and almost halved our ac bills. So besides cubic feet instead of sqft, it looks like one needs to consider where you live. Oy!
Nailed it, undersizing is good! By law not allowed anymore.
Manual J
Manual J, T and S are very important but J is the best start. Totally agree.
Manual J 💪 do a proper load calc. No rule of thumb. Houses are being built tighter and tighter now and more insulation.
DIY'ers typically dont care about RH and calculations. They just want heat or cool. I live in PNW and biggest issue I run into is ducting is incorrect and not so much units over or under sized.
550 square feet per ton is the rule of thumb. If you have high ceilings you might need to upsize a bit.
Never "estimate" A/C tonnage requirements! Always use a proper load evaluation! Also never trust a salesman. It's actually 'legal' to sell a 3 Ton unit that produces only 33,000BTUs. To reiterate the importance of load calculations, we have numerous homes in DFW with 2200-2400 sq.ft cooled by 27,000 BTUs just fine.
There is no set btu/ft^2 at all. You have to model the house with manual J to get that value and maybe even manual D
How about a log home with 1500 sqft downstairs with open living room and a separate unit for loft upstairs of 300 sqft? Built in 2002. In S.C.
I'm in the process of getting central air. I had 3 quotes and each one proposed a different unit size: 2, 2.5 and 3 ton. It looks to me they are pushing their stock instead following my needs.
i got a system size for the house like explain in this video, when it was 104 outside the system will continue to run and will not drop the indoor temp below. 80. had company come out that installed it, would say the system performing as it should. it was under sized when in USE but on paper it was correct size.
Manual J , is the only way .
Some other company published a manual with similar figures to Manual J.
It makes me laugh that Denver is in zone 5 on this chart. But that is why we follow the math, not the charts.
Generally, a 3 ton will cover 500 sq ft. in an 8 ft ceiling, vaulted ceilings and 2 story are special conditions.