Attic Mounted Central Air Systems

So today's post isn't about the entire central air system but rather focused on a common issue that pops up with horizontal attic mounted units equipped with air conditioning. Since we have an attic mounted unit, we know it has to be a split system with the condensing unit or heat pump located at the exterior of the structure.

The area I want to discuss today is the attic mounted "A-Coil" or "Evaporator". This is the portion of the system that extracts moisture from the air thus cooling the supply air. It produces water in the form of condensate much like your car air conditioning system does. The "A-Coil" is equipped with a primary drain pan located directly beneath the coil. It normally has a primary drain line made of PVC that runs to a sink drain somewhere in the structure. There is secondary drain line as well, this one is attached to the same drain pan but slightly elevated above the primary drain line. The secondary line typically will have open discharge termination above a window or patio door. This is done to provide a visible warning to the occupant that the primary drain line is not performing correctly, the water has now risen in the pan and reached the elevation of the secondary drain line. You should shut the system down when this occurs and seek service by a licensed HVAC Contractor.

The reason for the discharge into the secondary drain line can be any number of issues. Possible blockage in the line from debris or rodents. Dirt/debris in the coil which has fallen into the pan from not changing the air filters in a timely manner or even a poorly installed pan which didn't provide for proper slope into the drain system. For any of these reasons it is always prudent to have a secondary over flow drain pan system for these attic mounted units. Leakage from the primary system can cause damage to the coil, pan and or housing and begin to leak into the attic and or structure directly below same.  Remember, water can cause damage to the structure....