Air Handler | Fan Coils
An air handler, also known as fan coils, are found on several different types of Central HVAC Systems, but are most often matched to a heat pump system. Essentially, the air handler consists of a fan blower system, positioned behind a built in evaporator coil, electric heat element, or a combination of both in heat pump systems or AC only systems. When the fan blower turns on, the air is forced through the box and across the coil system, thus providing conditioned air (warm or cool) on the output side of the air handler and into the duct system of a home.
Air handlers can be positioned in either an upright position that is referred to as Upflow or DownFlow. The air handler can also be installed in a horizontal flow position where the air flows from side to side through the unit, which is most common in crawl spaces or attics. There are several other things to consider when you need to replace your existing air handler.
Refrigerant Types in the Air Handler
The air handler and outside unit must have the same type of refrigerant! This means that if you have a air conditioner or heat pump condensing unit outside your home that is charged with R22 refrigerant, the air handler must also be designed to work with R22. This is generally not an issue for most replacement units, as most often the indoor (Air handler) and outdoor (condenser) units will be changed out at the same time If you are only changing the outdoor unit, you MUST make sure the indoor air handler is capable of supporting the new unit. Higher efficiency (+13 seer) outdoor units are not likely to match up to any air handler that is more than 3-4 years old.
Sizing of Air Handlers and Fan Coils
Just like matching your refrigerant, the size of your indoor air handler should be a very close, if not exact size match, to your outdoor unit. In other words… if you install a 3 ton heat pump condensing unit outside, your indoor air handler MUST have a minimum of a 3-ton blower and coil. You NEVER want to have a smaller size indoor air handler, than that of the outdoor unit. If you do make this mistake, your system will end up freezing the coil due to adequate airflow.
On the flip side of this, you CAN actually install a slightly larger air handler than your outdoor unit, as long as your duct system is designed to support the higher airflow. For example, you can install a 3-ton condensing unit outside, with an air handler designed for a 3-4 ton unit. The design can be modulated to actually achieve a slightly higher efficiency, but this is something an unskilled homeowner should not attempt to do on their own, unless you are familiar with your equipment and the various blower settings of the air handler.