Air Handler Coils
The air handler coils should be checked for dirt and debris which may have been sucked into the air handler inadvertently. Some air handlers have the filters inside them before the coils. It is a good time to change the filters when making this check. Any dirt or debris on the coil(s) should be removed immediately as these things will impede airflow through the air handler and throughout the entire system as a whole. Some air handler coils are installed in the air handler cabinet while other coils are installed in the ductwork.

Air Handler Coils

A blocked air handler coil can also cause serious mechanical issues, especially for DX cooling applications. The air filter should catch most of the dust and debris but it always good practice to check the air handler coils to be sure nothing is impeding air flow. Some air handlers can have up to three coils inside them. These are usually commercial air handlers with a cooling coil, a hot water coil for heat, and a reheat coil for dehumidification purposes. All coils should be inspected for any blockage including algae growth. Again, a qualified HVAC technician can handle all the air handler maintenance checks on your air handler coils safely and efficiently.

Different Types of Coils for Air Handlers

For commercial air handlers and a few residential air handlers there can be more than one coil in the air handling unit. A few commercial air handlers can have three coils but only in rare circumstances for specialized HVAC applications. The coils can be either hot water coils, chilled water coils, or direct expansion coils with the direct expansion coils used as an evaporator coil in a refrigeration circuit. There are some residential air handlers that use either a hot water heater or a boiler for a hot water coil located in the air handling unit. On a call for heat, a circulator pump kicks on along with the blower. The air passes over the coil and picks up heat from the coil and hot water inside the coil. Commercial air handlers can have hot water coils for heating and a chilled water coil for cooling purposes. Hot water coils can be either preheat coils or reheat coils and both coils can be used for heating while a

On a call for heat, a circulator pump kicks on along with the blower. The air passes over the coil and picks up heat from the coil and hot water inside the coil. Commercial air handlers can have hot water coils for heating and a chilled water coil for cooling purposes. Hot water coils can be either preheat coils or reheat coils and both coils can be used for heating while a preheat coil is typically used to preheat cool air coming from a mixing box or economizer and a reheat coil is used for either heating or for dehumidification purposes.

AHU Coil Types

Direct expansion (DX) coils are typically either a slab coil, an A-Coil, or an N-Coil with each coil serving its own purpose for configuration and heat exchange inside the air handler. The type of coil inside the air handler depends on the design requirements of the air handler and what the manufacturer has available for the design requirements. What is important about the coil is the heat exchange ability of the coils.

Copper with aluminum fins are considered the best for evaporator coils with some manufacturers offering special coatings on the coils to enhance the heat exchange ratio for better efficiency. Another factor with any coil that chills including DX or chilled water coils is the drain pan or drain pans under the coil that will catch the condensation when the coil is operating below the dew point. Some drain pans are constructed of metal and over time will rust through and leak water from the drain pan. The drain pans also are prone to algae growth and collect all kinds of muck one can find in an air handler. Treatment for the air handler coil drain pans.

Some drain pans are constructed of metal and over time will rust through and leak water from the drain pan. The drain pans also are prone to algae growth and collect all kinds of muck one can find in an air handler. Treatment for the air handler coil drain pans is available from your local HVAC supply house.

Maintenance for Air Handler Coils

Maintenance for the air handler coils is important as it does not take much dirt and other volatile organic compounds to collect in the coil and impede air flow. This is why air filter maintenance is imperative. Additionally, that ultraviolet air cleaner (UAV’s) are used to prevent mold and mildew growth inside the air handler and on the coils. When and if the coils become dirty it is necessary to clean the coils thoroughly to ensure there is no dirt, VOC,s or debris in the coils that will impede air flow. When the coils are cleaned it is important that the condensation drain pan is cleaned and flushed as well.

Cleaning the coil is important as well as cleaning the drain pan and the drain pipe. Sometimes the drain pipe can be plugged with debris or algae growth and when the drain pipe plugs it overflows the pan or pans if the unit is equipped with a secondary drain pan.

High Performance HVAC

Air Handler Coils

 

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