Which air conditioner should I get?
Before answering this question, we want you to know that Great Degrees will work for you to ensure that the air conditioner model selected for your application:
- meets your needs and expectations,
- provides quality comfort,
- is properly sized,
- is properly installed, and
- is reliable.
There are three main items to consider when choosing an air conditioner today. They are efficiency, condenser staging, and indoor unit blower motor type. These items are discussed below. By understanding the different choices which can be made in these three categories, you will be able to select an air conditioner that appeals to you. Great Degrees will analyze your existing system's air distribution system and overall performance (if applicable) and other specific details of your application. We will then perform an air conditioning load calculation to ensure what you like is in fact appropriate and is sized to the specific needs of your application.
High-Efficiency or Mid-Efficiency?
High efficiency air conditioners typically achieve their higher efficiencies through the use of larger size coils, multistage compressors, and indoor blowers with variable speed motors. Energy efficiency requirements have resulted in the the phase out of lower efficiency equipment. The lowest efficiency equipment available today is actually better termed mid-efficiency equipment. Although it is the lowest efficiency available, it typically uses much less energy than the equipment it replaces. Higher efficiency equipment is typically bigger than less efficient equipment. As such, the outdoor unit (condenser) may take up more space, requiring a larger mounting pad and trimming back of nearby shrubbery, or because of space constraints, it may need to be installed in a slightly different location than your existing unit. All this can result in higher installed cost. However, the savings on energy bills offsets this. More efficient units have lower power requirements, reducing the cost of wiring them for electric power. With current tax credits, if you qualify, the net installed cost of a higher efficiency ends up being competitive with that of a mid-efficiency unit. Also, you will save on electricity costs versus your less efficient air conditioner. By installing a new air conditionig system, most people will save a minimum of 23% on electricity costs. Many people will save even more, particularly if installing a high-efficiency air conditioner with multistage compressor and an indoor unit with variable speed blower. Due to constraints, a high efficiency air conditioner may not be appropriate for you or your particular application. Mid-efficiency air conditioners are a good alternative under such conditions. These air conditioners utilize single stage compressors and do not require an indoor unit with a variable speed blower.
Single-Stage or Multi-stage Condenser?
Typical air conditioners have single-stage condensing units (i.e. an outdoor unit with a single-stage compressor and single speed condenser fan motor). These condensing units are either on or off. More sophisticated air conditioners have multistage compressor units. Instead of being either on or off, multistage burners are able to vary their cooling capacity to more closely match the load created by the outdoor conditions and internal heat gains. The result is more even comfort in air conditioning mode, because such multistage air conditioners run more continuously on a lower speed when compared to a single-stage air conditioner of the same total cooling capacity. In addition to ensuring more even comfort, less starting and stopping is associated with multistage air conditioners. The net result is that multistage air conditioners experience less wear and tear on their components, and they provide better overall efficiency. Multistage condensing units are available that run at two discrete levels of output, as well as models that are completely modulating (run at variable speed). Air conditioners with more stages or which completely modulate provide the most even comfort.
Multispeed or Variable Speed Indoor Blower?
The indoor blower circulates your conditioned air. If you heat with a forced air furnace, then the air conditioning system will typically use the furnace's blower. If you do not heat with a forced air furnace, then an air handler unit will be used to circulate the indoor air for the air conditioning system. Whichever is used, a furnace blower or a blower built into an air handler unit, the blower choices are the same, multispeed or variable speed. Multispeed blowers are older technology. They start up quickly. Variable speed blowers ramp up to speed slowly, and they also ramp down slowly when turning off. As such they are much quieter than multispeed blowers which instantly start at full speed. Multispeed motors typically have three or four speed taps (wire leads), two of which are typically used for your particular application (one speed for heating and one speed for air conditioning; the remaining speeds go unused). In addition to starting and stopping more quietly, variable speed motors use somewhat less electricity than multispeed blowers. Depending on how you run the blower, the savings will be more or less. If you run your blower continuously, and if you do not need it to run on high speed continuously, then the variable speed blower will provide more savings when compared to a multispeed motor not capable of running as such low speeds, and as such, is forced to run at a higher speed to provide continuous circulation of the air. Variable speed blowers cost a bit more than multispeed blowers, but the quieter starting and stopping, along with the energy savings is worth it to many people. If you are contemplating installing an entirely new system for a home, complete with air distribution system (duct work), then if you plan to zone the ducts with dampers, a variable speed blower will propably do a better job for you than a multispeed motor. Within certain limits, variable speed motors will deliver the same amount of air flow as static pressure varies. This means your equipment's efficiency will not vary as dampers open and close when compared to similar equipment operating with a multispeed blower. Air flow through multispeed blowers varies as dampers open and close. This can result in more adverse impact on comfort and efficiency when the multispeed blower is used instead of a variable speed blower in a system with zoning dampers. If you have an existing furnace, and if you wish to upgrade the blower type from multispeed to variable speed, then you will probably need to change the furnace.
Summing Up
Features within any one category above are mutually exclusive. That is, you cannot get an air conditioning system with both an indoor blower which is both multispeed blower and a variable speed blower, nor can you get a air conditioner which is both high efficiency and mid-efficiency. However, between the categories, air conditioners are available with all combinations of features. For example, you can get a high efficiency air conditioning system with two-stage condensing unit and a variable speed indoor blower. Or you can get a mid-efficiency air conditioning system with single-stage condensing unit and multispeed indoor blower. Choose the combination of features which you feel are best for you.
