Can I Replace Just the Outdoor Unit on an Older Air Conditioning System to Save Money?

When part of your air conditioning system fails, you may be tempted to replace just one unit instead of the entire system. This can be especially tempting if you haven’t noticed anything wrong with the second unit. While this may seem like the most logical solution, the two units in air conditioning systems actually work in tandem, and replacing one without replacing the other usually results in a mismatched system.

How Do Air Conditioners Work?

Air conditioners have an indoor and outdoor unit, each of which is involved in the process of removing heat from your home. Refrigerant flows through the system through copper tubing. The refrigerant absorbs heat at the indoor evaporator coil and transfers it to the outdoor unit. The compressor squeezes the liquid refrigerant at the condenser, and the absorbed heat is released outside. The process continues in both units until your home reaches the desired level of cooling.

The Importance of Matching Components

Since the indoor and outdoor units work together to create a cooling effect, it can be inefficient to replace just one of the units and not the other. Replacing just one can lead to frequent repairs, higher operating costs and a shorter lifespan for the system.

Properly matching old and new units is difficult for the following reasons:

Older coils aren’t as efficient and can put undue stress on a system when matched with a newer coil. Matching old and new coils can result in poor cooling capacity and a higher use of energy, and may make another component, like the motor or compressor, fail.

Newer air handler/evaporator units achieve higher SEER (seasonal energy efficiency ratio) ratings, but when they’re matched with older condenser coils, they can’t reach that high rating.

Today’s coils have new and improved physical features like grooved surfaces and enhanced tubing. When these coils are matched with older ones, they aren’t compatible.

New units have thermal extension valves that better control the refrigerant and thus boost performance. In order to work correctly, they have a hard shut-off valve, but this valve is detrimental to older compressors.

The American Society of Heating, Refrigeration and Air Conditioning Engineers has performed tests to determine the detriment of matching older and newer systems. This data has helped solidify the necessity of replacing an entire system instead of just an indoor or outdoor unit.

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