Patent ID: 6931882

Claim:
A dual function condensate drain trap for positive or negative pressure air handling unit or positive or negative pressure air duct connected to a drain pipe and located on one side of an air handling unit to prevent air from flowing in or flowing out and to drain condensate water, comprising: the drain trap having a water inlet and a water outlet located on two sides connecting to a drain pipe, the drain trap including a valve seat and a retaining element resting on the valve seat, the retaining element being movable between a first position to be in contact with the valve seat in normal conditions and a second position to be not in contact with the valve seat, when the pressure of the water column of the water inlet is smaller than the pressure of the water outlet, the retaining element being located on the first position, to form an air lock and so that air cannot enter or escape from the air handling unit, when the pressure of the water column of the water inlet is greater than the pressure of the water outlet, the retaining element being moved to the second position to drain water, the drain trap being coupled with an extension of the drain pipe that is in parallel with a ground surface; wherein by changing the drain trap connection port, the drain trap is selectively used with positive or negative pressure.