AC Condensate Drain Calculation Guide + Free Excel Sheet & Online Calculator
Introduction – What Is AC Condensate Drain Calculation?
Air conditioning systems remove moisture from indoor air as part of the cooling process. This moisture becomes condensate water, which must be drained safely. Correctly calculating the condensate water production and sizing the drain line ensures proper operation and prevents water damage or clogs.
In this post you’ll find:
- A free Excel condensate drain calculator
- A link to an online calculator tool
- Condensate calculation formulas
- Pipe sizing guidelines
Online AC Condensate Drain Calculator (Free Tool)
For fast condensate drain sizing based on system capacity, you can use the online calculator here:
👉 AC Condensate Drain Calculator – Drain Pipe Sizing Tool:
🔗 https://tools.mepbase.com/ac-condensate-drain-calculator
This tool helps you determine the recommended drain pipe diameter for split units, AHUs or FCUs based on cooling capacity.
Free Excel Condensate Drain Calculation Sheet
You can also perform your own condensate calculations using a downloadable Excel sheet. This spreadsheet lets you:
- Calculate condensate production based on airflow and humidity differences
- Estimate annual condensate volume
- Size condensate lines and plan drain routes
Condensate Drain Calculation Formula
To estimate the amount of condensate produced in an AC system, use this common HVAC formula:
Condensate flow (GPM) = (M_air × ΔW_air) / (V_air × 8.33)
Where:
- M_air = Airflow rate in CFM
- ΔW_air = Change in specific humidity
- V_air = Specific air volume
- 8.33 = Conversion to gallons per pound of water
This gives you gallons per minute of condensate, useful for sizing drains and traps.
How to Size a Condensate Drain Pipe
A condensate line must be sized properly to prevent pooling and provide smooth gravity drainage. The online tool linked above helps with pipe recommendations based on cooling capacity:
- Up to ~5 TR → 3/4″ pipe
- 5–10 TR → 1″ pipe
- 10–20 TR → 1-1/4″ pipe
- 20–40 TR → 1-1/2″ pipe
- 40–80 TR → 2″ pipe
Note: These sizes are general engineering suggestions; always check local codes and conditions.
Best Practices for AC Condensate Drains
- Slope the drain line at least 1/8″ per foot for proper flow
- Use traps and cleanouts where appropriate
- Insulate horizontal lines in humid environments
- Avoid routing drains across finished ceilings without protection
AC Condensate Drain Calculator Excel
Conclusion
Proper calculation of air conditioning condensate drain requirements is essential for reliable HVAC performance and avoiding moisture problems. Use the online calculator tool linked above for quick pipe sizing, or the Excel sheet for more detailed analysis. Both tools support better system design and planning for MEP professionals.
