What size house will a 3.5-ton air-conditioning unit cool? A 3.5-ton air-conditioning unit cools homes from 1,801 to 2,300 square feet, depending on location. The unit cools 1,801 to 2,100 square feet in southern states from Georgia to California, and it covers 2,101 to 2,300 square feet in northern states. For existing systems, model numbers reveal the unit capacity. What is a ductless air-conditioning system? What is retrofit air conditioning? Manufacturers use a code in the model number of outdoor units instead of listing unit capacity on the air conditioner. If the model number is CKL42-1, for example, the unit is 3.5 tons. The number 42 means the unit is 42,000 British thermal units; when divided by 12,000 Btu per ton, the result is 3.5 tons. Alternatively, residential load calculations can scientifically determine the proper size air-conditioning unit. How much space can a 2-ton air conditioning unit cool?A building's energy efficiency, including air leak...

What is the cost to install an air conditioning unit in a 1,600- square-foot house?If the duct work of the central a... To put Freon in an air conditioner you will need a Freon kit with compatible refrigerant, gloves, goggles, a mask and access to your air-conditioning unit....ac unit runs inside but not outside Where can you buy a replacement air conditioner fan?car air conditioning repair manual What is a gas ceiling heater ?air conditioner small room portable What are some good plans for a backyard guest house? Are there Trane installation manuals available online? Where can you buy Whirlpool Gold dehumidifiers? What is the average size of a billiard table? 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. An 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. To remove the moisture, however, the air conditioner needs long runtimes. 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 ConditionerResidential Air Conditioning & Heating Service 1. What size HVAC system should I have? Contrary to popular belief there, is no rule of thumb for sizing a system to a home. Depending upon the construction of your home, one (1) ton of air conditioning can cool anywhere from 300 to 800 square feet of home. The only way to insure the size of the system you purchase will be large enough to cool your home, but not any larger than you need, is to have your home’s individual cooling and heating needs evaluated by a licensed professional. 2. How are the sizing capacities of heating and cooling systems measured? The heating and cooling systems are sized according to their tonnage. One (1) ton equals 12,000 BTU/H. Residential systems can range from 1- 5 tons. 3. How is the efficiency of an air conditioning system measured?

The SEER (seasonal energy efficiency ratio) is the amount of cooling your system will deliver per dollar spent on electricity. The EER (Energy Efficiency Ratio) of a particular cooling device is the ratio of output cooling (in Btu/hr) to input electrical power (in Watts) at a given operating point. The higher the SEER and EER, the more efficient the system will be. The SEER has the same units of Btu/W·hr, but instead of being evaluated at a single operating condition of 95F ambient, it represents the expected overall performance for a typical year’s weather in a given location. 4. How can I increase the efficiency and life of my home’s cooling and heating systems? One of the best things you can do to extend the life of your HVAC equipment is to clean and replace your filters as needed. In addition, yearly maintenance in the spring and fall is highly recommended to ensure the system is operating at peak efficiency. 5. Is a larger system better? No. A larger system with more capacity delivers less comfort and costs more to operate.

An air conditioner is at its lowest efficiency at start up. A system with too much capacity will cool the house too fast (short cycling), turning on and off repeatedly over an extended period. Also keep in mind that an air conditioner only removes humidity when it’s running, so a system with shorter run cycles doesn’t remove humidity from the air very well. 7. Should I try to keep my system from running too much? Every time your system starts up, it uses a lot of electricity and may not produce much cooling. Usually a system that is too small to cool the home is more economical to run but delivers less comfort. Even though it runs nonstop, it will usually consume less power than a larger system that cycles on and off. As a rule of thumb, a unit that is either on or off is less expensive than one cycling on and off. 8. What temperature should I set my thermostat? Obviously, the time of year becomes a big factor for desired temperature settings. In summer months, the average temperature setting is 76°-78°, and 69°-71° during the winter.

Remember, when leaving your house; try to avoid drastic temperature changes. Do not set your temperature back more than 5°; this will cause your unit to work harder to achieve the desired temperature setting. 9. What are programmable thermostats and what are their advantages? There are numerous programmable thermostats available on the market today that offer many new and exciting features. And because they are electronic, they are more accurate and efficient than thermostats that contain mercury. With programmable thermostats you can control the temperature in your home at different times of day without ever touching your thermostat. Because everything is automatic, you will never forget to change the setting on your own. 10. How often should I have maintenance done on my air conditioner and what can I do on my own?How long do you want your HVAC system to last? In order to ensure maximum efficiency and life span, you should have planned maintenance performed on your air conditioning system twice a year.

This allows us to foresee any potential problems and prevent costly breakdowns. Our Planned Maintenance Agreements (PMA) can be custom designed for your home or office. 11. How much does a new replacement system cost? Due to the numerous brands and models, equipment should be determined by the individual’s specific needs. For example, air quality, humidity control, and overall efficiency can be dramatically improved by installing better equipment. So, depending on the situation, this question can best be answered by doing a thorough evaluation of your home and your existing situation. We offer some excellent financing options to make your investment convenient. There is never a charge for an in-house energy assessment from one of our comfort advisors. 12. Are there any air conditioning systems that are safe for the environment?All manufactures have developed new systems that contain the environmentally friendly R410A, or Puron, refrigerant. 13. Why are humidifiers used more in heating than cooling?

When cool outdoor air enters a home it tends to dry out as it warms up, which increases the static electricity in the home and causes sinus problems. Adding a humidifier will help add moisture back into the air and limit sinus problems. In the summer, humidity levels are already high and the goal becomes to dehumidify the air, or take out moisture in the air. This water vapor is called condensation. The average comfort range for relative humidity in a home is from 40-50%. 14. During the heating season, my heat pump delivers warm air, but not hot air, and will operate for long periods of time. This was a common problem with heat pumps for many years, but manufacturers have come a long way in heat pump design and engineering. New heat pumps can produce supply temperatures of 110F+. Yes, this is normal. 15. How do I know if my A/C unit is big enough? Before purchasing any replacement equipment for your home, you should make sure your system is sized properly. Your ductwork has a big impact on how well your system operates as well.