Condensate Drain Trap Depth from Fan Static
The dimension condensate-drain only mentions in prose.
Example
You enter
- Unit configuration draw-through
- Max static pressure, worst case (in w.c.) 2
- Drain pipe diameter (in) 1
- Insulation thickness (in) 0.5
You get
- H (trap depth) 3.00 in
- J (in) 1.5
- L (clearance needed under the pan) 6.00 in = H + J + pipe + insulation
Details, formula, and sources
Manufacturer trapping geometry: draw-through H = 1 in per 1 in of negative static plus 1 in, outlet leg J = half of H, and total clearance L = H + J + pipe + insulation; blow-through H = static plus 1/2 in. A 2-in w.c. draw-through unit needs a 3-in trap, 1.5-in outlet leg, and 6 in of room under the pan. Both errors bite: too short loses the seal at start-up and pulls drain air into the airstream, too tall will not drain against the negative pressure.
Draw-through: H = (1 in per 1 in of maximum negative static) + 1 in; J = H/2; L = H + J + pipe diameter + insulation. Blow-through: H = 0.5 in + maximum total static; K = 0.5 in minimum.
Manufacturer condensate-trapping engineering guidance (Trane condensate-trapping bulletin), by name - the named dimensions H, J, K, and L are taken from its figures.
The bulletin is publicly available; equipment installation instructions carry the same dimensions per model.
Estimate. AHJ and licensed professional govern.
Field names used by the API: configuration, static_pressure_in_wc, pipe_diameter_in, insulation_in, h_in, j_in, l_in
- Draw-through geometry H = static + 1 in, J = half of H, L = H + J + pipe + insulationTrane condensate-trapping bulletin, negative-pressure figure
- Blow-through geometry H = static + 0.5 in, K = 0.5 in minimumTrane condensate-trapping bulletin, positive-pressure figure
- Worst-case static size on the dirty-filter condition, not the clean-filter numbersame bulletin