Replacing Your System


During some point of their ownership, many homeowners are faced with replacing their central heat and air-conditioning systems. The average life span of central heat and air-conditioning systems and heat pumps is 12 to 15 years if they are properly installed and recommended maintenance is performed.

When the system starts giving you more problems than you can afford to fix, it may be time to consider purchasing a new system.

It is important to know that split air-conditioning or heat-pump systems consist of two parts: an indoor (coil) unit and an outdoor (condensing) unit. These two parts are specifically designed to work together as a coordinated  "team"  to provide top performance and maximum efficiency and comfort.

In the past, homeowners could sometimes replace part of their system, such as the outdoor condensing unit, to extend its useful life. However, air-conditioning and heat-pump systems manufactured today, by law, must have a seasonal energy efficiency ratio (SEER) of 13 or higher. For these new, high-efficiency systems to work properly and to extend their life, the outdoor unit and indoor unit must be perfectly matched. So if you install a new high efficiency outdoor unit, but don't install a new, equally efficient and properly matched indoor unit, the results could be uncomfortable, frustrating, and expensive. Because newer equipment usually is more energy efficient than older, central air-conditioning or heat-pump systems, you will likely see reduced utility bills.

The Right Equipment

Homeowners should ask their air-conditioning technician to size the equipment to meet the specific needs of their homes. If a system is undersized, it will continuously run without properly cooling your home. If oversized, the system will cycle on and off too frequently, greatly reducing its ability to control humidity. It also will be less efficient.

To properly size a system for a home, trained technicians will use an equation that factors the home's age, the number and quality of its windows, how well it is insulated, how many stories it has, its total square footage, and local energy rates. Homeowners should ask their technicians to perform a Manual J analysis, the industry's term for the standardized equation used to properly size an air-conditioning system. Your technician will specify the cooling capacity of the system in either Btu/h (British thermal units of heat removed per hour) or refrigeration tons (one ton being equal to 12,000 Btu/h).

When installing a new air conditioning system, you will need to consider your home's electrical system. It is not uncommon for old houses to have only 110-volt, 60-amp service for the entire home -- barely enough power to handle the home's existing lights and appliances. Central air conditioners require a dedicated 230-volt circuit and may require 20 to 50 amps of power, making an electrical service upgrade necessary. Have an electrician evaluate your home's electrical supply before your HVAC contractor begins work.

Energy Efficiency

Air conditioning manufacturers are required by law to evaluate and rate their equipment according to its energy efficiency. This rating for central air conditioning is known in the industry as a Seasonal Energy Efficiency Rating (SEER) or Heating Seasonal Performance Factor (HSPF) for heat pump systems. The higher the SEER/HSPF, the more efficient the equipment. Generally, the higher the SEER/HSPF of a unit, the higher the cost, but the difference often can be recouped through reduced home energy bills.

Many manufacturers voluntarily submit their products for testing by the Air Conditioning and Refrigeration Institute (ARI) to assure consumers their energy efficiency claims have been verified by an independent, third party laboratory. However, ARI does not certify individual units, but matched air conditioning and heat pump systems, which work together as a coordinated team to achieve the given SEER/HSPF rating. Because the ARI Performance Certified seal is usually visible on the outside unit, it is important for consumers to double check their system is properly matched by asking their technician to verify this information.

Air conditioning and heat pump manufacturers are constantly engineering innovative technologies to improve the efficiency of their equipment. Two of those technologies that help keep energy bills down are the two-stage compressors and variable-speed motors.

Two-stage compressor

Two-stage cooling means the air conditioner or heat pump has a compressor with two levels of operation: high for hot summer days and low for milder days. Since the low setting is adequate to meet household-cooling demands 80% of the time, a two-stage unit runs for longer periods and produces more even temperatures.

Longer cooling cycles also translate to quieter, more efficient operation and enhanced humidity control. Compared to a single-stage unit, a two-stage air conditioner or heat pump can remove twice as much moisture from the air. This is important because when moisture levels are high, there's a higher potential for mold and other pollutant problems.

Variable speed motors

The indoor air handler (fan and motor) provides the energy to move air through the ductwork of a central air conditioning or heat pump system to the rooms of your house. In most standard central cooling and heating systems, the fan and motor runs at one speed, which means the system is either on or off. A variable speed motor (VSM) uses control technology, meaning the VSM automatically changes speed based on your home's heating and cooling requirements. It slowly increases up to maximum speed instead of coming on at full capacity all at once. This eliminates the sudden blast of air you feel with a one-speed system and results in the system running at a lower speed most of the time. This eliminates noisy start up, while reducing wear and tear on the fan and motor, resulting in a substantial reduction in operating costs due to major energy efficiency improvements.

Quiet Cooling

Most heating and cooling systems manufactured today are quieter than those produced in past years. But there are still significant differences in sound ratings among these products.

Consumers can look for sound-dampening features such as insulated compressor compartments, discharge mufflers and innovative fan designs that work to soften the sound of a hard-working, high-efficiency compressor. Top-panel orifices, compressor wrappers and indoor blowers are all designed to further promote smooth, quiet airflow.

Information provided by the Air Conditioning, Heating and Refrigeration Institute.