Expert article on how to properly size a whole-house air conditioner for your home. Included are tips for reducing the load on your air conditioning unit. Manufacturers produce whole-house central air conditioners in a range of sizes, which raises one of the most important questions you’ll have to answer when shopping for one: How big should it be? With air conditioners, the term “size” has nothing to do with a unit’s physical dimensions but, rather, its ability to produce cooled air. Both room-size and whole-house air conditioners are manufactured in a variety of capacities, so it’s helpful to understand how they are measured. An air conditioner’s ability to produce cooled air is measured in BTU (British Thermal Unit) per hour and in tons. A BTU measures heat output. One BTU equals the amount of energy needed to raise 1 pound of water by 1 degree F. One ton is the equivalent of 12,000 BTUs per hour, or the amount of energy it takes to melt 1 ton of ice in a day.

For one thing, the larger the capacity, the more a unit will cost since output is directly related to cost. Also, it’s important to pick a size that is appropriate for your house. An air conditioner that is too small can’t keep up with load requirements on a particularly hot day. One that is too large will cycle off and on too frequently, doing a poor job of dehumidifying the air, which degrades comfort. In fact, it’s better to slightly undersize an air conditioner than to oversize it. Also, the air flow into and out of rooms must be carefully balanced to ensure efficient operation of the system. These factors, in addition to how well a house is insulated, how it’s used by your family, your climate, and more must be taken into account when selecting and designing your system. Though you should consult a qualified air-conditioning contractor before making any purchase, you can estimate your requirements by figuring you will need about 1 ton of capacity for every 400 square feet of living space in a marginally insulated house.

For example, a 2,000-square-foot house would normally require about a 5-ton air-conditioning system; a newer, well insulated house can often be served by a smaller system. Featured Resource: Get a Pre-Screened Local Air Conditioning Contractortape for ac unit These simple measures will help you reduce your air-conditioning needs and save a bundle.window ac unit for walk in cooler When the weather gets hot, an air conditioner must work hard—that is, run frequently and for long periods—to keep a home at a comfortable temperature. ac unit spring maintenanceConsidering the energy cost of running an air conditioner, the net result of this is high utility bills. If you’re able to minimize the temperature in your home by other means, you can cut down on the work your air conditioner must do.

In fact, you can reduce the load on your central air-conditioning system by taking just a few simple measures. For starters, clean or replace your furnace or air handler’s filters. Clogged filters restrict the movement of air through the system, which reduces efficiency. Then consider the many improvements that can reduce your home’s heat gain such as utilizing heat-reflecting film on windows that face the sun, installing a foil radiant barrier in the attic, and improving your home’s insulation. Also to reduce heat gain you can simply pull shades or window coverings over sun-facing windows. Stir up breezes using a whole-house fan or ceiling fans, or circulate air using the “Fan Only” setting on the thermostat or equipment that controls your air handler’s blower. Also, when possible, minimize midday activities that add humidity to the air, such as washing clothes, showering, and cooking. Humidity makes the temperature feel warmer, and the air conditioner must work harder to remove humidity from the air.

For more helpful tips, see 9 Ways to Cool Your House for Less. 1,153 posts, read 2,496,428 times 2,387 posts, read 3,215,403 times Why not in attic...my husband wants it up thete snd I don't Originally Posted by deeds multiple studies by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) as well as studies by the National Renewable Energy Laboratory have shown that ductwork in the attic of residential dwellings is one of the single most in-efficient portions of an HVAC system + installation. In an NREL study, they estimated 15-25% energy savings purely ductwork being run in the conditioned envelope versus in the attic. This is a significant improvement even over increasing wall insulation the R19 or higher or attic insulation to R50, and also still better than even jumping all the way to a SEER 17 unit. It is done because it is easy and cheap, but it is inefficient and a huge energy waste in operation. If you are building new, you should do what you can to run the ductwork in chases / boxed out trusses etc.

Even a crawl space is better than running them in the attic. Think about it: during the cooling season, you are running your coolest air (off the evaporator coil) through the hottest part of your house (the attic). During the heating season you are running the hottest air (off the furnace or coil) through one of the coldest parts of your house (the attic). Poor sealing of ductwork and minimal insulation lead to dumping a lot of wasted conditioning directly to your attic space. Husband wants heating unit also in attic due to damp space under house I'd argue they are not concerns on the same level. I've never had rodent issues with hvac ductwork in the crawl space in any of my parents' houses I grew up in nor in our house. I prefer it inside the insulated envelope instead of the crawl space anyway; I was just saying crawl space is typically better than the attic in terms of energy efficiency. But in either case, I would say that I would take guaranteed energy efficient improvements (that will help evry time the unit is running) vs the small chance that you may ever have rodent issues with crawl space ductwork.