Why a correctly sized siphon matters

On an air handling unit, the siphon drains condensate from the collection tray while maintaining a water seal that prevents unwanted air ingress or leakage.

Its sizing depends on the pressure regime at the drainage point: under positive pressure (the fan pushes the air) as well as under negative pressure (the fan draws the air), the minimum heights a and b are calculated from the pressure differential [Pa] to guarantee correct flow without breaking the water seal.

Siphon under positive and negative pressure

The detailed instructions (Siphon – Depair user guide) and the associated sizing tools (K-factor, air damper sizing, valve and actuator sizing) are available in the Toolbox and the Documentation.

Size your siphon

Calculate the siphon height required, under positive as well as negative pressure.