Inside the Closet: Replacing an A-Frame Evaporator Coil

When homeowners open their hallway HVAC closet, they are usually greeted by featureless grey metal boxes. However, during a major system replacement, removing the front casing reveals the intricate copper engineering hidden inside. The photograph above captures a brand new A-frame evaporator coil mid-installation, sitting directly above a powerful indoor blower motor. This pyramid-shaped maze of copper tubes is the epicenter of the residential cooling process.

As the blower motor underneath forces hot, humid air up from the return grilles, the air is pushed through the thousands of ultra-thin metallic fins surrounding the copper tubing. Inside those tubes, freezing cold liquid refrigerant is rapidly expanding. As the hot air passes through the A-frame, its heat is instantly absorbed by the freezing refrigerant, and the humidity in the air is condensed into water droplets. The newly chilled, dehumidified air then continues upward into the ductwork, while the condensation safely drips down into a black plastic drain pan visible at the base of the coil.

Installing a new coil is a highly technical process requiring precise oxy-acetylene brazing. The thick copper lines covered in black foam insulation (the suction line) and the smaller, bare copper lines (the liquid line) must be flawlessly welded to the outdoor condenser unit to form a completely pressurized, leak-proof system capable of holding hundreds of pounds of refrigerant pressure. At SunDollar A/C & Heat, every brazed joint is pressure-tested with dry nitrogen to guarantee decades of flawless performance.