Your Air Conditioner’s Air Handling Unit
There are several parts to an air conditioning and heating system. They all work together to keep you home comfortable throughout the year. Knowing how these different components work together will improve your understanding of the essential function of the Air Handler in the HVAC system of your home.
The split system air conditioning unit consists of two parts, the air handler and the condensing unit. Your air handler is usually located in a closet, the attic, or your garage. In a split system, your compressor/condensing unit is usually located outside of your house.
If your air conditioning system is a package unit then the air handler and comdensing unit will be included as a part of the single packaged unit.
Your air handler performs the function of moving the air throughout your living space. Contained within the air handler are the evaporator coils, blower motor, and some of the HVAC system controls. Your air handler may be an up or down flow or a horizontal flow unit.
The air filter is most commonly located in the return register, however sometimes it can be found in the air handling unit itself or in a return duct. Ask your HVAC service professional where the filter is located for your system so you can make sure it is replaced on a regular basis.
Filtering the air not only improves the quality of air in your home, but it is necessary for the effective operation of your air handling unit (AHU). If air filters are not changed frequently, then dirt, dust and debris will build up and drawn in through the return vent. This inadequately filtered air can cause the evaporator coil to become blocked. When your coils become blocked, your heat exchanger will operate at higher than recommended temperatures. This lack of proper filtration will cause the unit to operate less and less efficiently and can reduce the lifespan of your unit.
The Air Handler’s Evaporator Coils
Your air conditioner’s evaporator coil carries the refrigerant within the coil. The coil and refrigerant absorb the heat from the air passing through the coils during the heat exchange process. Heat absorbed during this process causes the refrigerant inside of the evaporator coils to boil and change state. The refrigerant that enters the coils is mostly a liquid. By the time the refrigerant reaches the end of the coils, the heat it has absorbed will be enough to turn it into a vapor.
On the outside of your air handler there are two copper pipes. One is a large insulated line and one is a small uninsulated line. The suction line is the large insulated line. This large line transfers the vaporized refrigerant back to the air compressor. The uninsulated smaller line is referred to as the liquid line. The liquid line carries the liquid refrigerant from the condensing coils back to the evaporator in your AHU. If your unit is running then the large suction line should be cold and the small liquid line should be hot.
The temperature of these two lines is partly dependent on the ambient outdoor temperature and the heat in your house.
A significant problem that some people experience with the evaporator coils is clogged coils. This may happen as a result of a collapse duct, or if the coils are plugged with debris or dirt, or if too many supply vents have been closed in your home.
For your evaporator to work properly the evaporator coils must be free of any blockage and have good airflow. Replacing your air filter will help filter out particles before they clog the evaporator coils.
Your Air Handler’s Blower Fan Motor
The blower motor typically consists of a few different components. It will include an electric motor and a cage, often referred to as a squirrel cage. Some units have belt driven motors, however most have direct drive motors on the blower fan.
Maintenance for the blower motor usually consists of oiling the oil ports or if it is belt driven a check on the condition of the belt.
Condensate Lines for the Air Handler
For those homes where the air handler is located in the attic, it is critically important that the condensate line is checked to make sure it is not clogged. Since the evaporator coil runs at a temperature that is less than the dew point it will condense the moisture in the surrounding air.
The evaporator coil is designed to get rid of excess moisture into a drain pan.
The majority of drain pans have a 3/4” PVC line fastened to it that permits excess moisture to drain to the outside of the house. Occasionally the PVC line becomes blocked with algae or other muck and needs to be cleaned out to clear the obstruction and prevent overflow.
If you air handler is installed in your attic it should have a secondary drain pan with a float switch as a backup safety measure. The float switch will shut down the unit if the secondary drain pan begins to overfill. No homeowner wants to reinstall their ceiling because a float switch and a secondary drain pan were not installed or were not checked for blockages.
Protect your investment in your HVAC system and your home by taking the necessary steps to maintain the major systems responsible for your building’s performance.
At Anderson Service we recommend two maintenance visits a year from an HVAC professional contractor to avoid cost repairs, improve your home comfort level, and extend the life of your air conditioning and heating system.
Preventive maintenance can save you money and prevent hardship.
