Like so many powerful innovations, central air conditioning is easy to take for granted. The cool, dry air that whispers unceasingly from wall and ceiling registers can lull us into a false sense of security. Then an electric bill arrives, or the system starts to falter. Suddenly we realize that basic maintenance was called for--just cleaning the air filter would have cut cooling costs 5 to 15 percent. Or perhaps it's time to replace an old and inefficient central air conditioner. There are a number of options to consider, including high-efficiency systems that can reduce electrical cooling costs 20 to 30 percent. Here's a crash course in the mechanical system that helps you keep your cool when temperatures start to climb. Conventional central air systems graft into a house that has ducts for forced-air heating. The hot and noisy portion of the cooling system, the compressor-condenser, is located outside. The cool and quiet component, the evaporator coil, is located inside, above the furnace blower.

Cool, dry air is distributed; warm, humid air returns to be cooled and dried.%" align="center" style="padding:2px;border-right:1px solid #ccc;">%" align="center" style="padding:2px;border-right:1px solid #ccc;">%" align="left" style="padding:2px;border-right:1px solid #ccc;">Houses heated with boilers lack ducts to distribute cooled air. They can be centrally cooled with mini-duct systems in which an evaporator coil, fan and trunk duct are located in the attic. Cooled, high-velocity air is piped from the trunk duct through flexible, insulated plastic ducts.>A ductless split system is the answer for many homes that are not centrally cooled or that need more cooling after an addition is built. The compressor-condenser serves one or more evaporator coil fan units installed on the inside walls of the house.The Refrigeration CycleMechanical, chemical and thermal energy act together in your central air-conditioning system to cool and dehumidify indoor air. Warm liquid refrigerant is driven under high pressure toward the evaporator coil.2.

Near the evaporator, the liquid flows through a metering device that functions like a garden-hose nozzle. It converts the warm, high-pressure liquid into warm, low-pressure droplets.3. As the droplets enter the evaporator coil they begin to cool, and the droplets are transformed into cold vapor.4. A fan blows warm, humid indoor air over the cold coil. Moisture in the air condenses and drips off the coil into a pan to be drained or pumped away. The gas in the coil warms as it removes heat from the indoor air.5. When the compressor turns on, it draws the warm gas toward its suction port. The gas enters as a warm vapor and leaves hot and at high pressure. Now it enters the condenser, and as it makes its way through the labyrinth of tubing, it gives up its heat to air moved by the condenser fan. The gas condenses into a warm liquid ready to repeat the cycle. The Lennox SunSource is a heat pump with a solar assist. Its condenser fan motor draws power from a 190-watt photo­voltaic panel, a $3000 add-on.

The high-efficiency heat pump itself costs $4000 to $7500, depending on the installation. The equipment runs the refrigeration cycle in reverse for winter heating, so it achieves energy gains year-round, not just in the summer cooling cycle, accelerating the energy payback of the photo­voltaics. how much to replace ac unit in homeIn most cases the solar panel is installed in a sunny location, either on the roof or the side of the house. outdoor ac unit coversWiring then runs from the panel to the fan motor.window ac unit rentalEquipment CheckThe best way to ensure a steady flow of cool, dry air this summer is to do a little basic maintenance this spring."The key to maintenance is air flow," according to PM contributor Pat Porzio, a heating-cooling contractor and mechanical engineer.

Ensure that air can move freely through the compressor-condenser by using a shop vacuum to remove grass clippings, leaves, dryer lint and any dust discharged from a central vacuum system. If the equipment is near a dryer vent, check it weekly.Clean dirty compressor-condenser fins using specialized foaming cleaner, sold at supply houses and on the Web. Don't use household cleaners, which can cause corrosion. Rinse the fins with a garden-hose nozzle pointed down, not horizontally, to avoid blasting dirt into the equipment. .+ Check the air filter monthly and replace it when necessary.+ Keep the thermostat set at 78 F.+ Seal leaky ducts with mastic and tape to prevent loss of cooled air and infiltration of dust and dirt into the duct system.+ Seal gaps around the home that allow cool air to escape.+ Open vents that were closed during the winter.Central air conditioning seems like a good proposal for most homeowners, especially if you live in an area that’s warm or hot all year long. Add on the adoption of smart home automation, you can stay cool during the summer while being energy efficient.

But air conditioning isn’t necessarily a panacea. It has downsides you need to consider before making this purchase. Let’s have a look at some benefits and drawbacks of central air: That’s the major benefit of this type of air conditioning: A consistent temperature everywhere in your home, all year long. If you live in a southern area, or somewhere with very hot summers, it’s the best way to keep your home cool, constantly, in every room. That’s the most common reason why homeowners buy this type of air conditioning. Pushing cooled air to every room of your home can increase your energy bill if you’re moving from no air conditioning at all to central air conditioning, obviously. According to Energy.gov, “In an average air-conditioned home, air conditioning consumes more than 2,000 kilowatt-hours of electricity per year.” If you don’t have an air conditioning unit already installed, consider that your energy bill will increase dramatically, especially if you like your home around 68 degrees.

You can save money by increasing the overall temperature to 72 degrees or 73 degrees, turning it down at night and keeping it well maintained. If you think you only need a few rooms cooled, such as your bedroom and the living room, consider buying window air conditioning units. It’ll be more efficient, and it won’t increase your energy bill by as much as a central unit. One of the other benefits of this system is the air pushed through the ducts is filtered. The air quality of your home will improve, which means fewer allergens and potentially harmful gases. However, this benefit requires maintaining and changing the filter regularly. Modern units have filter indicators that’ll tell you when you need to change your filter. If you live in an area with high levels of humidity, filtering the air also means lowering the humidity level. This increases the comfort level of your home, too. However, keeping your air clean will require frequent duct maintenance, as bacteria and mold can build up if you don’t.

You’ll need to keep a close eye on the cleanliness of the ducts and have them professionally cleaned at least once a year. If you live in a northern state with colder winters, you’ll be happy to learn that packaged units contain both an air conditioner and a heater. This means you can simply choose a temperature for your home, all year long, without having to worry about dealing with two different systems. It also makes your entire home more efficient, since you only need to deal with one unit instead of two, or several. Often, this is what the decision comes down to: ductwork. If you already have it — from a furnace system, for example — then all you need is to hook up the air conditioning unit to your home’s duct system. However, if you don’t, you’ll need to consider the fact installing ductwork is a major renovation that involves opening up walls and floors. Although it’ll certainly increase the value of your home in the long run, it’s a major investment that’ll require planning and a good budget.