Air Handler Spring Maintenance Checks

Spring maintenance checks to the air handler can help you avoid costly repairs when the heat of summer arrives. A word of caution is advised here before you open the panel. Air Handlers have high voltage running into them and there is a shock hazard. Before you remove the panel make sure the power is turned off to the unit. Only a professional should operate the unit with the panels off. Even with the thermostat in the off position the unit has high voltage running into it. Turn the circuit breaker off before opening any panel on your heating and air conditioning equipment. The air handler contains the evaporator, metering device (on most units), the blower, and some controls. The metering device and the controls should be checked by a professional. These components are highly technical and beyond the scope of this site to explain in detail. The evaporator and blower can be maintained by the homeowner as long as safety and common sense are applied.

Checking the Evaporator

The evaporator coil carries refrigerant inside it. This coil and refrigerant, through the heat exchange process, absorbs heat from the air passing through the coils. The heat causes the refrigerant inside the evaporator coils to boil and change state. The refrigerant, where it enters the coil, is mostly a liquid. By the time it reaches the end of the coils it should have absorbed enough heat to change it from a liquid to a vapor. On the outside of the air handler there are two copper lines. One large and insulated line, and one small and uninsulated line. The large line is the suction line. This line carries the vapor (refrigerant) back to the compressor in the condensing unit. The small line is called a liquid line. This line carries liquid (refrigerant) from the condensing coils to the evaporator. When the unit is running the liquid line should be hot and suction line should be cold. The temperatures of these lines will vary depending on how hot the house is inside and the ambient temperature outside the home. A big problem most people encounter with the evaporator coils is blocked coils. The coils are plugged with dust, dirt, and other debris, there is a duct collapsed somewhere, or there are too many supply vents closed off in the home. For the evaporator to work properly and efficiently the coils must be clean and have plenty of air flow. Thus, the necessity of a good filter to filter all the particles from the air before it reaches the coils. Coils operate below the dew point when the air conditioner is on. This will make the evaporator coil wet so when the dust makes contact with the coil it will often stick to the coil. Over time this will cause a build up and eventually the system will stop cooling. With improper air flow across the coils there is no heat exchange process. The coils will freeze and ice will form on them. Another cause of ice forming on the evaporator coil is a low refrigerant charge. If the coils are clean and they are icing up, you need to call a professional to charge the unit properly.