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All refrigerated air conditioners, whether individual room units or central systems, operate according to the same principle: they extract heat and moisture from the room air, cooling and dehumidifying it, then return the air to the room. Refrigerant, the same sub-stance that’s used in a refrigerator, circulates through the system.

How refrigerated systems work. Inside a refrigerated air conditioner are a compressor, evaporator or cooling coils, a condenser, and connecting tubing; all are filled with refrigerant. Liquid refrigerant forced through a nozzle expands and partially vaporizes into a gas. The gas then flows through the evaporator coils, cooling the coils so they extract heat and moisture from the room air (the moisture condenses on the coils).

The warm gas then flows into the compressor, where the gas is heated by compression so it exceeds the outside temperature. From the compressor, the hot gas enters the con-denser. There, the hot condenser coils dissipate heat to the outside, and the gas condenses into a liquid, ready to repeat the cycle.

A Typical Room Air Conditioner

Types of refrigerated air conditioners. One type, a room air conditioner, is very easy to operate; units can be installed in as many rooms as needed. Another type is central air conditioning, which either can be an independent system with its own blower and ducts or can be combined with a forced warm-air heating system, in which case it uses the same blower and ducts as the heating system.

Room air conditioners
A room air conditioner is mounted in a window or wall; most of the unit projects outside the house.

A blower in the unit sucks warm room air through a filter protected by a large inlet grill on the front of the unit; cool, dehumidified air returns to the room through outlet grills. Water condensing on me evaporator coils drains outside, and a fan blows outside air around the condenser coils to dissipate heat.

Cleaning the Filter

Cleaning the Condenser Coils

Little maintenance is required. During the cooling season, clean the filter and condenser coils every month (see facing page, bottom); replace the filter as necessary. You can reach the filter either through a slot on the side or top or by removing the grill. To reach the condenser, remove the back of the outside housing. Problems with the refrigeration system are best left to a professional.

Central air conditioners
Though the initial expense is higher, central air conditioning is generally more efficient, quieter, and less costly in the long run than individual room units.

In a house without forced warm-air heat, a central air conditioner can be a single unit installed next to the house or a split unit, with the condenser and compressor outdoors and the evaporator and blower inside.

For a house heated with forced warm air, the most economical installation is a split system (see at right). The evaporator is mounted in the plenum of the furnace, and the condenser and compressor are located outside the house.

A Split-Type Central Air Conditioner

To ensure efficient operation clean the filter every month during the cooling season; replace the filter as necessary Check that the condensate drain is clear and that the condense and evaporator coils are clean. When you vacuum the coils, be careful not to damage or deform the fins.

For problems with the operation of your air conditioning system, see the chart below. Call in a professional to repair the refrigeration system.

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Air conditioners are a blessing in hot climates. Not only do they cool the air, but many dehumidify and filter the air as well. The two most common types of air conditioning systems for the home are evaporative and refrigerated. Both can cool just a single room or an entire house; most types are controlled by a thermostat.

Evaporative air conditioners, also called swamp coolers, work well in dry desert regions. Refrigerated units, though more expensive to purchase than evaporative ones, are the only way to cool air in other than desert climates. Included in the category of refrigerated units are both room air conditioners, fitted into a wall or window, and central air conditioning. An-other type of refrigerated system, a heat pump, cools and heats a house (see below).

The energy cost of most air conditioning systems is high. For this reason, it’s important that your system be properly maintained and, if necessary serviced by a professional.

The descriptions below and on the next pages will help you become familiar with the different systems. To ensure long, reliable operation, be sure to follow the few simple maintenance steps outlined for your particular system.

Evaporative Air Conditioners
In hot, dry areas, evaporative air conditioners are the most efficient way to cool a home. The unit is mounted in full sun on the roof or beside the house.

Inside the unit, water is sprayed on porous, absorbent blankets. Hot out-side air pulled through the blankets by a blower causes the water to evaporate, cooling the air. The cool air then enters the house, forcing stale air out through open windows.

With conscientious maintenance, you can expect few problems. At the beginning of each cooling season, and more often if you see a mineral buildup from the evaporated water, thoroughly clean the unit, oil the pump and blower, and replace the blankets. Also, check and adjust the blower belt; if it’s cracked or worn, replace it as for a belt in a warm-air furnace.

A Typical Evaporative Air Conditioner

How a Heat Pump Works
Basically, a heat pump is a refrigerated air conditioning system in which the air flow is instantly reversible.

During warm weather, the pump draws heat from the air inside the house, cooling it and transferring the heat to the outside or to a large solar mass. During cool weather, the flow is reversed heat extracted from the outside air or from a large solar mass heats the air inside the house. Once the thermostat is set at the desired temperature, the heat pump automatically heats or cools your house as required.

In climates where temperatures below 0F are common, either electric heating elements or some other supplemental heat source is required. Whenever the heat pump cannot ex-tract enough heat from the outside air, the supplemental system turns on.

If you add an electric air cleaner and, to compensate for dry winter air, a humidifier, your heat pump system will provide clean air at the correct temperature and humidity for 24 hours a day.

Be sure to keep the outdoor portion of the heat pump free of snow and debris. Occasionally check the blower and filter, and replace the filter monthly when in use.

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Modern thermostats for heating or air conditioning systems rarely break down. The only maintenance required is an occasional light cleaning. Don’t attempt to repair a defective thermostat; instead, replace the entire unit with a new one. Be sure the replacement is the correct voltage and type for your system.

To install a new thermostat, follow the illustrations below.

How thermostats work. Thermostats are switches that are turned on by a temperature-sensitive device that, in turn, activates the switch controlling the operation of a boiler, furnace, electric heater, air conditioner, or other heating or cooling device. Low-voltage and millivolt thermostats are the most common types.

The three principal parts of a thermostat are the heat sensor, the switch, a, in low-voltage types only the heat anticipator. The sensor, usually a bi-metal coil, contracts as it cools, tripping the switch to “on,” and expands as it warms, tripping the switch to “off.”

The switch may have open contacts (in older models) or a mercury- type contact enclosed in an airtight glass tube. The anticipator prevents the living area from overheating by shutting off the boiler or furnace just before the desired temperature is reached.

Cleaning a thermostat. Gentle cleaning will help keep a thermostat operating efficiently First, you’ll need to remove the cover of the thermostat. Then follow the instructions below to dust the heat sensor and, if your thermostat has them, exposed contact points and switch contacts.

Cleaning a Thermostat

Installing a Thermostat

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