Why Must an Air Conditioner Condensor Match the Evaporator?

Whole building air conditioners are split systems consisting of outside components — the condenser and compressor — and an inside component, the evaporator coil, that work in conjunction to remove humidity and cool indoor air temperature.

Split System Operation

Air conditioning condensors must match evaporator coils to achieve energy efficiency.Air conditioning condensors must match evaporator coils to achieve energy efficiency.
Most split system air conditioners have an average life of 15 to 20 years, with the exterior portion failing first while the interior evaporator coils remain operational. Evaporator coils should be replaced along with the condenser and compressor to achieve maximum efficiency.

Split system air conditioners use fluid, called a refrigerant and four main components: A condenser, a compressor, an evaporator coil and an air handler or furnace. The system may be thought of as having a cold side, with the evaporator and a fan that blows air over coils cooled by the refrigerant, which arrives from the outside unit via copper tubing. In turn, the refrigerant flows back to the outdoor, or hot side of the system, taking with it heat that it absorbed through the evaporator coils. The compressor squeezes the heat out of the refrigerant, while the condenser releases the warm air into the outside environment.

Proper Sizing

A number of factors go into attaining maximum energy efficiency when selecting and installing a new air conditioning system. Proper sizing, determined through heat load calculations is key. These measurements ensure that the system’s British Thermal Unit, or BTU, output is appropriate for the application. For the system to run as efficiently as possible, however, the main components must also match in size. These are the indoor evaporator coil, outdoor condensing coil, or condenser, refrigerant tubing, circuit breaker, and fuses and electrical wiring.

Federal Guidelines

Air conditioning components must also match because of a U.S. Department of Energy mandate that required all systems sold beginning in 2006 to have a seasonal energy efficiency ratio, or SEER, of 13 or higher. This mandate effectively eliminated the sale of 10 SEER and 12 SEER units. In addition, the mandate also required the reduction in production of R-22 refrigerant, also known as Freon. Only R410a, or Puron, refrigerant is available with new systems. All components must match when the condenser is of a different size or capacity, the newer refrigerant is used, coils are designed for lower efficiency ratings or to achieve a specific SEER rating.

Consequences of Mismatching

In addition to not reaching maximum energy efficiency, mismatched evaporator coils and condensers often lead to failure of the new condenser and compressor within two years when an existing evaporator coil is used. The warranties of many systems are also rendered invalid if matching components are not installed.