Heating, Cooling and HVAC

Is it better to leave the fan running continuously with the air conditioner or to place it in the automatic position?
It is more efficient to leave the thermostat in the automatic position.
The fan consumes only one-tenth the energy of the compressor, but when it runs continuously, the fan can cost up to $30 a month.

This amount can be reduced by cycling the fan only when it’s needed.
Additionally, the air conditioner will dehumidify the only air when the compressor is running. However, if the fan remains on after the compressor cycles off, some moisture on the coil will re-evaporate. This moisture must be removed during the next compressor cycle, which increases the energy consumption.

If air distribution is poor within the home or business and hot spots or very cold areas result, the fan can be run to even out the temperatures.

However, the fan should be set to the auto position when the building is unoccupied. Even better, shut the air conditioner off or raise the thermostat setting when leaving the building.

Will I save energy by turning off my air conditioner when I leave home, or am I better off just letting it run?
If gone for four hours or more, more energy will be saved by turning off the air conditioner or turning up the thermostat.

During the day, keep windows shut and close curtains or blinds on any windows that will be exposed to sunlight.

The thermal mass of the house will probably keep the indoor temperature well below the outdoor temperature, and the house should cool quickly when the air conditioner is restarted. Use a programmable thermostat or timer to turn on the air conditioner 30 to 45 minutes before the expected arrival home. If the home is still warm upon arrival, turn on a fan to create air movement.

Moving air can make the air feel about four degrees cooler than it really is.

Can you plant bushes to hide the outside of my air conditioner?
When landscaping around an outside condensing unit, remember that the air conditioner must reject all the heat from a home.

Although it is possible to plant bushes near the condenser, leave room for adequate air circulation. Without good air circulation, the temperature near the condensing unit will rise. The higher temperature will reduce the capacity of the air conditioner, causing it to work harder and provide less cooling. This could also kill the shrubbery.

If the shrubs will not form a continuous wall around the unit, plant them so that, when they mature, there will be three feet of clearance. If the shrubs will be continuous, then allow five feet of clearance.

Are there any simple checks I can perform to see if my air conditioner is operating properly?
Check a few items that should indicate if the air conditioner has problems.
First, check the two lines connected to the outside of the air conditioner.

The larger on -- the suction line — should be cool to the touch. It should not be so cold, however, that frost develops.

The smaller line -- the high pressure line — should be warm, but not hot. It should be 20 to 30 degrees warmer than the outside temperature. In extreme cases, it will be hot to the touch, so be cautious. If this is the case, call a service technician.

Some air conditioners are equipped with a sight glass in the high-pressure line (the small line). The glass should be clear, with no bubbles visible, while the system is running. Cloudy liquid in the sight glass may indicate contamination of the system.

One final check is to measure the temperature of the air as it leaves the register. It should be 15-20 degrees cooler than the room temperature.

If the building is warm, humid, or if the ductwork is not insulated, then there may be smaller temperature differences.

These guides are not intended to eliminate the need for an annual check by a qualified service person. If problems are suspected, call for help from someone familiar with air conditioners.

Would I be better off using several window air conditioners?
Using multiple window air conditioners has both advantages and disadvantages. A distinct advantage of window units is that they can operate individually. This flexibility allows cooling only the occupied room rather than the entire house.

A central system is more convenient to operate when cooling the entire home continually, and possibly at a lower cost of operation.

If sound level is a consideration in the home, keep in mind that window units are typically noisier than central air conditioning.

In terms of efficiency, top-of-the-line central units are generally more efficient than window units.
Look at the seasonal energy-efficiency ratio (SEER) when selecting units — the higher the SEER, the higher the efficiency under similar conditions.

Since there are positives and negatives about window units and central systems, consider personal needs and preferences before choosing a system.

What is a ton of air conditioning?
A ton is the measure of the cooling capacity of an air-conditioning unit. It is an indication of the rate that the unit removes heat from a building.

One ton of air conditioning removes 12,000 British thermal units (Btu) of heat an hour. The term was derived from the time when ice was used for refrigeration. One ton of air-conditioner cooling capacity removes the same amount of heat required to melt 2,000 pounds, or one ton, of ice in 24 hours.

Typically, residential central air conditioners will range in capacity from one and one-half to four tons. Window units will many times be rated in Btu per hour. For example, a 6,000 Btu/hr. window unit would have the capacity of one-half ton.

Sources :http://www.engext.ksu.edu/ees/henergy/space/air.html#adding