It's been hot and muggy in Atlanta the past few days. Now I'm not your typical Atlantan who says that lightly. I grew up in Houston and south Louisiana and spent nine years in Florida, so I know hot and muggy. Overall, summers in Atlanta are pretty nice because of our elevation (~1000 feet), but we do have our moments. Anyway, it's been hot enough that we've hit our summer design temperature, which is defined as the temperature exceeded only 1% of the time. In Atlanta, the summer design temperature is 92 degrees Fahrenheit. That's the temperature at which air conditioners ideally will provide exactly as much cooling as the house needs, when sized according to the Manual J cooling load calculation protocol developed by ACCA, the Air Conditioning Contractors of America. When outdoor conditions are at the design temperature, an air conditioner should run pretty much continuously and be able to keep the house at the ACCA recommended indoor design temperature of 75 degrees Fahrenheit.

When outdoor conditions go above the design temperature, the AC should run continuously and not quite keep the house at 75 degrees. Now, the thing is, Manual J has some built in oversizing, so even if the air conditioner were sized according to an accurately performed Manual J load calculation, it's not going to run continuously at the summer design temperature. It should run long enough to make the house comfortable, however. Last week I wrote about the 4 factors of comfort, temperature and humidity being the first two. what size ac unit do i need for my garageAn air conditioner actually does two jobs - it lowers the temperature and removes moisture from the air, thus taking care of the first two factors, with HVAC design anyway.cheap wall ac unit To remove the moisture, however, the air conditioner needs long runtimes. small ac unit for room

That's because the air moving over the cold evaporator coil causes the water vapor to condense. The more air moves over the coil, the more water condenses out and gets carried away. It takes about 15 minutes of runtime before you start getting serious dehumidification of the air, so oversized systems will not dehumidify well. If the AC comes on, runs 10 minutes or less, and then shuts off, the house may be cool, but in a humid climate, the indoor humidity levels will stay high, probably over 60%. I know this from personal experience. Last year we replaced the AC in our condo, and I did the Manual J load calculation. The result was that we needed a 1.6 ton air conditioner for our 1500 square feet, so we had a 2 ton system installed. Knowing that Manual J has a built-in oversizing bias, I wanted to go with the 1.5 ton system, but I chickened out. Our AC runs maybe 15 minutes max on a hot afternoon, and our relative humidity stays around 60%. The Manual J bias is real, and it's not small.

And that's with an accurate HVAC load calculation. I've seen plenty of load calculations that use incorrect inputs so the contractor can come up with a cooling load to match the AC size he wants to install. Now, back to the point of this article - how to tell if you have an oversized air conditioner. Just get your stop watch and time how long the AC runs on a hot afternoon. Ten minutes or less, and it's definitely oversized. Twenty minutes would be OK. Thirty minutes at a time or longer, and your humidity levels should be fairly low. So, how long does your air conditioner run on a hot day? See my followup article with real data on our AC runtimes: My Big Fat Oversized Air ConditionerTrane Air Conditioners Price List Trane makes one of the most complete lines of central air conditioners on the market.  This Trane air conditioners price list will provide an overview of their models as well as offer sample pricing for each one.  The prices we offer are not straight from Trane but are gathered through reader input as well as our monitoring of the market. 

The reflect average prices for Trane products currently being offered.   The Trane product family is divided into four categories: Ultra Efficiency, Super Efficiency, High Efficiency and Standard Efficiency. Ultra Efficiency: Trane XL20i This is the Trane top of the line central air conditioner, the Trane XL20i.  This Energy Star product is characterized by outstanding efficiency of up to 20 SEER which may reduce air conditioning costs by 50% or more when it replaces models 10+ years old.  Here are other top features that affect the cost: 2 ClimaTuff scroll compressors provide sufficient performance to cool on even the hottest days. ComfortLink II technology coordinates system components for better efficiency and performance. Comfort-R humidity control uses managed cycles to reduce humidity when cooling. 4 models are offered: 2, 3, 4 and 5 ton. 12-year limited compressor warranty; 10-year coil and parts warranty. Trane Air Conditioners Price List for the Trane XL20i Air Conditioner

2 ton Trane XL20i central air conditioner: $1,989 3 ton Trane XL20i central air conditioner: $2,249 4 ton Trane XL20i central air conditioner: $2,579 5 ton Trane XL20i central air conditioner: $2,819 Super Efficiency: Trane XL15i Air Conditioner This very efficient Trane central air conditioner also offers the ComfortLink II communicating technology that offers superior performance and indoor comfort.  Here’s what else is offered in the XL15i: Single- and 2-stage ClimaTuff compressor. WeatherGuard top for enhanced protection, air flow and noise reduction. 9 separate models offered from 1.5 ton to 5.0 ton capacity.10-year limited coil and parts warranty. Trane Air Conditioners Price List for the Trane XL15i Air Conditioner 2 ton Trane XL15i central air conditioner: $1,559 3 ton Trane XL15i central air conditioner: $1,829 4 ton Trane XL15i central air conditioner: $2,179 5 ton Trane XL15i central air conditioner: $2,499

High Efficiency: Trane XR15 Air Conditioner This is one of Trane’s most popular models because it offers the best balance between efficiency and affordability.  It’s an Energy Star-rated product with 17 SEER performance.  Quality materials and design are featured throughout the unit.  Top features for comparison include: Spine fin coil for more effective heat transfer. Quick-sess cabinet to expedite maintenance and service. Composite, corrosion-free base pan. 10-year limited compressor warranty; Trane Air Conditioners Price List for the Trane XR15 Air Conditioner 2 ton Trane XR15 central air conditioner: $1,539 3 ton Trane XR15 central air conditioner: $1,759 4 ton Trane XR15 central air conditioner: $1,989 5 ton Trane XR15 central air conditioner: $2,299 Standard Efficiency: Trane XB14 Air Conditioner Even Trane’s standard efficiency models are Energy Star-rated!  That says something about their commitment to their consumers and the environment. 

The Trane XB14 achieves up to 16 SEER performance when matched with a compatible variable-speed blower.  The other top features include: Aluminum fins on the compressor are efficient and resist corrosion. 10-year limited warranty on the compressor; 5-year limited warranty on all other parts. Trane Air Conditioners Price List for the Trane XB14 Air Conditioner 2 ton Trane XB14 central air conditioner: $1,159 3 ton Trane XB14 central air conditioner: $1,379 4 ton Trane XB14 central air conditioner: $1,599 5 ton Trane XB14 central air conditioner: $1,799 All Trane central air conditioner models now use R-410A refrigerant which is much more environmentally safe.  Each unit is housed in a heavy-gauge galvanized cabinet that is powder-coated for appearance and longevity.  WebHVAC Terms of Use - Some of the brands and products seen on this website are delivered through a relationship with outside suppliers like QualitySmith, Service Magic, Amazon, eBay, Google, and others.