CONDENSATE PIPE SIZE CALCULATOR
What size condensate drain pipe size do I need for my AC system?
The new calculator uses full psychrometric analysis to accurately determine condensate flow and recommend the minimum drain pipe size. To use the calculator, follow these steps:
1. Outdoor Design Conditions Select your city from the drop-down list (Australian summer design conditions are pre-loaded) or enter outdoor dry bulb and wet bulb temperatures manually. Also select whether to use 1% or 2% summer exceedance values.
2. Air-Side Parameters Enter the outside air flow rate and return air flow rate (both in L/s). Also enter the return air dry bulb temperature and room relative humidity. The calculator will determine the mixed air condition entering the cooling coil.
3. Off-Coil Conditions Enter the leaving air dry bulb and wet bulb temperatures off the cooling coil. These are used to calculate the actual moisture removed by the coil and the resulting condensate flow rate.
4. Pipe Options Select your preferred pipe material (HDPE SDR11 or Copper Type B to AS 1432, or both for comparison) and the drain slope. The calculator applies Manning's equation assuming half-full pipe flow per AS 3500.2.
The calculator will provide:
Condensate flow rate in L/hr
Total, sensible and latent coil heat removal in kW
Sensible Heat Factor (SHF)
Minimum recommended drain pipe size with a sizing table showing acceptable and undersized options
Notes:
The diameter of the drain line should be at least as large as the connection provided on the evaporator drain pan
Provide insulation for the first 3m run of condensate drain from the indoor unit to prevent surface condensation on the external pipe
If the condensate line is under negative pressure (e.g. connected upstream of the supply air fan), a drain trap is required
Results are indicative only and do not replace professional engineering judgement
