1. WHAT IS THE FUNCTION OF AN AIR CONDITIONER?
Your home air conditioner’s job is to transport heat from within to outside, cooling you and your home. Air conditioners cool the air in your home by sucking the heat out of it. The atmosphere is cooled by blowing it over a series of cold pipes called an evaporator coil. This is similar to the cooling when water evaporates from your skin. The evaporator coil is filled with a refrigerant, which converts from a liquid to a gas as it absorbs heat from the air. The refrigerant is pumped outside the home to another coil, losing heat and returning to liquid form. The exterior coil is called the condenser because the refrigerant condenses from a gas to a fluid, much like moisture on a cold window. A compressor transfers the refrigerant between the two coils and modifies the refrigerant pressure so that all of the refrigerant evaporates or condenses in the proper coils.
The motor that drives the compressor consumes the energy required to do this. The total system will typically provide three times the compressor’s cooling power. This strange phenomenon occurs because converting the refrigerant from a liquid to a gas and back again allows the system to move far more energy than the compressor.
2. WHAT IS A ‘TON’ OF COOLING?
Before refrigerated air conditioning, cooling was accomplished by storing large blocks of ice. When cooling units first became popular, they were assessed by the equal amount of ice melted in a day, which is where the term “ton” comes from when sizing air conditioning.
A ton of cooling now equates to 12,000 BTU/hour of cooling. BTU is an abbreviation for British Thermal Unit (a unit that the British do not use). The BTU measures heating (or, in this case, cooling) energy. Remembering that a window air conditioner typically weighs less than one ton is more crucial. A small central air conditioner for a home weighs roughly two tons, whereas a large one weighs about five tons.
3.WHAT WENT WRONG
Unlike most furnaces, air conditioners are sophisticated mechanical systems that rely on a wide range of conditions to function well. They are sized to handle a specific “load” on the house. They are intended to contain a particular amount of refrigerant, known as the “charge.” They are built with a specific quantity of airflow across the coils in mind. When any of these factors change, the system will have issues.
If you generate extra heat indoors due to more people, appliances, or modifications in the house, the air conditioning may be unable to keep up.
If the system’s refrigerant charge leaks, it reduces its capacity. Said you will get less cooling, and the system will be unable to keep up when the load is high.
If the airflow over the outdoor (condenser) coil is lowered, the system’s ability to reject heat outdoors is diminished, and the system’s capacity may be reduced, especially at higher outdoor temperatures.
4. WHAT ARE THOSE FILTERS FOR?
Almost every air conditioner has a filter located upstream of the evaporator coil. This can be a fuzzy-looking or folded paper filter in the return grille or unique slots in the duct system. This filter eliminates particles from the air stream, which helps to keep the air conditioning system clean while also removing particles from the air.
As the filter works, it becomes increasingly clogged with particles. This has the effect of increasing efficiency, but it also increases resistance and decreases airflow. When this occurs, it is time to replace the filter. The time it takes depends on how unclean the air is and how large the filter is.
If the filter is not changed, the air flow will decrease, and the system will work poorly. Also, if the filter becomes too dirty, it becomes a source of air pollution.
Removing the filter completely will fix the low air flow problem, but your victory will be fleeting. The particles the filter would have removed will now accumulate on your evaporator coil and cause it to fail. A new filter is far less expensive.
5. CARE FOR THE SYSTEM
Most customers can manage routine maintenance, such as changing filters, but some require expert assistance.
Brushing debris and obstructions from the coils and drains at the start of each cooling season is a good idea. Depending on the system and the consumer, this may necessitate a professional service call.
If the system isn’t producing as much cold air as it should, it could be due to a refrigerant charge issue or airflow issues. These issues may necessitate service.
6. DUCTS ARE VERY IMPORTANT.
Another reason systems are producing insufficient cold air is duct leakage. If the ducts flow outside the cooled space (this includes attics, crawlspaces, and garages), duct leakage can drain 20 to 40% of the energy from even the most efficient air conditioner. Outside ducts must be suitably insulated. Several solutions are available specifically for insulating ducts that a knowledgeable homeowner or a professional contractor can install.
If you plug your leaky ducts, you can acquire an extra half-ton of air conditioner capacity for free. If the ducts are accessible, the vents can be sealed with mastic—that white sticky stuff you can paint on the ducts. Otherwise, you’d need to hire an expert to plug the ducts.
7. HOW TO BOOST ENERGY EFFICIENCY
Sealing leaky ducts is the most important thing you can do to enhance efficiency. Still, many of the above concerns will also help: replace dirty filters, maintain proper charge and airflow, and clean the coils.
Another thing to check is that the outdoor (condenser) unit is not so buried that the airflow is obstructed or that leaves or other debris are not fouling it.
When replacing an air conditioner, seek high-efficiency technology. Seasonal Energy Efficiency Rating (SEER) is the most well-known efficiency rating. The minimal efficiency to consider is SEER 13, although higher efficiencies will likely be fairly cost-effective.
You can explore various efficiency statistics depending on your climate. For example, in hot, dry climates, look at the Energy Efficiency Rating (EER), which indicates how well the system will perform under peak conditions. Consider how well the unit dehumidifies if you reside in a hot, humid region.
8. LIFT YOUR LOAD
You may improve the performance of your air conditioner by lowering the amount of work it needs to do. This can be accomplished by upgrading the building or reducing the internally generated loads your air conditioner must handle.
Improving a structure’s ” envelope ” includes raising insulation levels, shading windows, and reducing air leakage. Such modifications will save energy for heating and cooling, but they may take time or money. Employing high-efficiency items when installing a new roof or windows is normally more cost-effective. For example, “cool” roofing can save half a ton of cooling and energy over a year.
Internal load reduction can be simplified. Turn off all unnecessary electrical appliances, lights, and equipment. Use appliances (such as washers and dryers) during cooler hours of the day. Local exhaust fans can remove heat and humidity from kitchens and bathrooms. Purchasing Energy Star or other high-efficiency equipment also helps.
Other strategies can be utilized in some climates to minimize the load on the air conditioner. In dry climates, evaporative air conditions (the modern equivalent of “swamp coolers”) can provide significant cooling. You can lower the load in areas with substantial temperature changes, such as hot, dry climates, by bringing in huge amounts of cool outdoor air. These systems are known as “night cooling,” “ventilative cooling,” or “residential economizers.”
9. VENTILATE
The preceding principles concentrated on cooling, but the original definition of air conditioning includes more: an ideal air conditioner should heat, chill, clean, ventilate, humidify, and dehumidify as needed to ensure health and comfort. The original definition’s second most important goal is to provide ventilation. Ventilation is required whether or not the equipment known as an air conditioner delivers it.
Contaminants created indoors can cause major health and comfort issues without proper ventilation. ASHRAE recommends that there be enough ventilation to exchange the air inside the house once every four hours, depending on the design of the house.
Older homes tend to have leakier walls and ducts, but they still provide adequate ventilation. Such leakage and infiltration may be more energy-efficient ventilation methods, but it is a potential source of savings.
Because most new homes and some existing homes are relatively tight, mechanical ventilation is required to meet minimal ventilation standards.
10. IT’S THE HUMIDITY, NOT THE HEAT.
The challenge that prompted the necessity for air conditioning was humidity management. In hot, humid conditions, a lack of humidity control can lead to mold growth and other moisture-related issues. High indoor humidity levels might cause health and comfort issues.
Modern air conditioners dehumidify as they cool, as evidenced by the water that drains away. However, this is secondary to their primary function of reducing temperature. They are unable to adjust both temperature and humidity separately.
In hot, humid locations, incidental dehumidification may not always be sufficient to maintain acceptable interior humidity levels. (At 78°F, ASHRAE recommends a maximum relative humidity of 60%.) Maximum dehumidification occurs not during hot seasons when the air conditioner is turned on frequently but during mild seasons when the air conditioner is turned off frequently.
Although some cutting-edge air conditioning systems offer to control humidity independently, conventional methods may need help to prevent the problem adequately. They can cause comfort or mold issues in certain conditions. Some modern high-end systems offer enhanced dehumidification. However, a stand-alone dehumidifier may be required if the existing system cannot sufficiently dehumidify.
Consumers can reduce the requirement for dehumidification by doing the following:
Set your thermostat to the “fan on” setting. In this position, the fan constantly blows air, whether your cooling system is working or not, and one significant effect is that most of the moisture your system just extracted from the air is pushed back into the home before it can drain.
During moisture-producing operations, use exhaust fans. Cooking, bathing, washing, and other related activities generate significant moisture within the home. Using a fan, direct that moisture outside. Similarly, avoid drying clothing indoors unless you have a clothes dryer that exhausts directly outside.
Please don’t open the windows or use ventilated cooling when it’s too humid outside.
10 Points to Assist Consumers
These ten ideas will make consumers more aware of their air-conditioning systems, allowing them to better care for and use them. If it becomes necessary to replace that system, seek the services of a certified HVAC specialist, ideally an ASHRAE member.
