The role of evaporator coils (also known as DX coils) in HVAC systems
In my last post, I covered condenser coils, which are found in outdoor units. This week, I’ll focus on evaporator coils, also known as direct expansion (DX) coils, which are found in indoor units. The two coils work together and are often located in close proximity to each other within an HVAC system.
The evaporator coil acts a heat exchanger, working with your heating system in the winter and your cooling system in the summer. It operates with the air conditioner or heat pump to condition and cool indoor air that flows over it by extracting moisture and heat.
In summer, as liquid flows into the evaporator coil, it expands and cools. Since the liquid is cooler than the surrounding air, it absorbs heat out of the HVAC system ductwork. The cooled air is then distributed throughout the ducts in the building, lowering the temperature in the building.In winter, the heat pump pulls air in from the outside and runs the air over the evaporator coil. The colder air is warmed by the evaporator coil and then pumped through the ductwork to heat the building. Even if the air outside the building is below freezing, the HVAC system is able to pull some heat from it.There are several common types of evaporator coils:
• Vertical evaporator coils are best suited for upward or downward airflow, condensing heat from pre-processed air into water form. After the condensation process, the vertical evaporator coil sends the water to a drain, lowering the humidity of the household air as it cools.
• Cased evaporator coils have a protective outer shell and are similar in function to vertical coils, but vary in shape and size. Like vertical coils, they handle upward or downward airflow, using coolant to attract hot air, which cools the airflow. The cold air returns to the home after passing through the air conditioning ducts.
• An uncased evaporator coil is a version of the cased coil, but without the protective outer shell. Uncased evaporator coils are much easier to customize, and good choice for uniquely shaped furnace and air conditioning units.In terms of shape, for commercial HVAC systems, slab evaporator coils are typically used. For residential HVAC systems, A-frame coils and N coils are more common.If you need help selecting the best evaporator coil for your HVAC system, just give us a call.