Condensate Rate and Drain Size
The gallons per hour a coil sheds from the tonnage, the minimum drain-line size by IMC 307.2.2.
Example
You enter
- Cooling capacity (tons) 3
- Condensate rate (pints/ton-hr) 3
- Horizontal run (ft) 20
- Slope (in/ft) 0.125
You get
- Rate pints (hr) 9.0 pints/hr
- Rate (GPH) 1.125
- Minimum drain size 0.75 in
- Fall over run 2.50 in
Details, formula, and sources
The gallons per hour a coil sheds from the tonnage, the minimum drain-line size by IMC 307.2.2, and the fall over a run at the code slope. The per-ton rate is an editable field estimate, since condensate tracks the latent load.
rate_gph = tons x pints_per_ton_hr / 8. Drain size by IMC 307.2.2 capacity steps (3/4 in to 20 tons, then 1, 1-1/4, 1-1/2, 2 in). fall = run x slope (>= 1/8 in/ft per 307.2.5).
IMC 307.2.2 (drain size by capacity) and 307.2.5 (slope) (by name).
IMC free read-only at codes.iccsafe.org; the size steps are stated, not reproduced.
Estimate. AHJ and licensed professional govern.
Field names used by the API: tons, pints_per_ton_hr, run_ft, slope_in_per_ft, rate_pints_hr, rate_gph, min_size_in, fall_in
- Condensate rate default 3 pints per ton-hour, editable; about 2 to 4 is common in humid cooling. Tracks the latent load, not a code valuefield estimate
- Drain size steps IMC 307.2.2 by equipment capacity; 8 pints per gallonIMC 307.2.2
- Slope not less than 1/8 in per foot toward the discharge (IMC 307.2.5); a draw-through coil needs a trapIMC 307.2.5