Air Handling Unit Condensate Drain Design

A cooling coil s drain pan opening is located at the point in an airflow system where the air pressure either positive or negative is the greatest.

Air handling unit condensate drain design.

Three quarters of an inch is sufficient for up to 20 tons according to the imc unless the drain outlet size is larger than in ch. One primary function of the air conditioning system is to dehumidify the air by removing water as it passes through the air handler. Collected in a drain pan below the cooling coil as illustrated in figure 1 the water must be removed to prevent damage and contamination to the air handler system and building. To find the design condensate drain one needs to know the design inlet and outlet air conditions precisely the moisture content and air flow rate.

The difference between inlet and outlet conditions of the moisture content gives the condensate flow rate. However more often than not in older larger buildings with multiple ahus many condensate pans are decades old and worn with age rusted corroded poorly sloped or clogged. The air handling unit sometimes furnace is the indoor portion of a split system and is often located in an attic space or within a basement. Imc 307 2 2 tells us that an a c condensate drain inside diameter should not be smaller than 3 4 and should not be smaller than the drain pan outlet diameter.

3 4 is sufficient for up to 20 tons according to the imc unless the drain outlet size is larger than 3 4. Further details on this month s topic are available on the drm website. And maintained air handling units including associated condensate management can minimize the potential for moisture carry over and associated damage and costs. A c condensate drains pumps.

For cooling coils condensate traps accumulating condensate to drain off while preventing air from entering a draw thru unit or escaping a blow thru unit. Chapter 6 section 2 air handling systems. In the case of the residential hvac system the condensate removed from the air falls to a drain pan within what is known as the air handling unit. Contained within the air handling unit is the coil which accumulates the condensate and it is then disposed of as water in liquid form.

If an air handling unit ahu is leaking condensate the purpose of the condensate pan a k a drip or drain pan is to catch and effectively drain the water.