How to Calculate FAHU Condensate: A Comprehensive Guide

Understanding how to calculate Fresh Air Handling Unit (FAHU) condensate is essential for professionals in the HVAC industry. Properly calculating condensate can help in designing efficient systems, preventing water logging, and ensuring the longevity of the system. As search engines prioritize high-quality content, our guide is structured with SEO optimization in mind, making it not only informative but also easily searchable.

What is FAHU Condensate?

First and foremost, let's define what FAHU condensate is. In simple terms, condensate from FAHUs is the moisture that is extracted from the air during the cooling process. As the FAHU cools the air, it reduces the air's ability to hold moisture, causing the excess moisture to condense and collect as water.

Factors Influencing Condensate Amount

Several factors can influence the amount of condensate generated:

  1. Ambient humidity: The more humid the environment, the more condensate you can expect.
  2. Temperature difference: A greater temperature difference between the incoming air and the cooling coil will produce more condensate.
  3. Airflow rate: As the volume of air processed increases, so does the potential amount of condensate.

Step-by-Step Guide to Calculate FAHU Condensate

Now that we've understood the factors, let's dive into the steps to calculate the FAHU condensate:

  1. Determine the volume of air: This is typically expressed in Cubic Feet per Minute (CFM) or Cubic Meters per Hour (CMH). You can find this in the specifications of the FAHU or measure it directly.
  2. Calculate the moisture content: Using a psychrometric chart, find the grains of moisture per pound (GPP) or the equivalent metric measure for the incoming air and the air after it has passed through the cooling coil.
  3. Find the difference in moisture content: Subtract the GPP of the air after cooling from the GPP of the incoming air. This gives you the difference in moisture content, which is the amount of moisture removed from the air.
  4. Convert to a measurable quantity: Convert the GPP difference to a quantity you can measure. Typically, this conversion factor is:For Imperial: 7,000 grains = 1 pound of water

    For Metric: 1 gram of water = approximately 0.016 grains (exact conversion can vary)

  5. Multiply by airflow: Multiply the difference in moisture content by the volume of air being processed. This will give you the total condensate produced either in pounds or kilograms per unit time, depending on your measurement system.
  6. Convert to a practical volume: If required, you can further convert the weight of the condensate to volume (liters or gallons). Remember, 1 kg of water is approximately 1 liter, and 8.34 pounds of water is about 1 gallon.

Importance of Accurate Calculation

Ensuring an accurate calculation of FAHU condensate is vital for:

  1. Designing proper drainage: Without the right drainage, water can accumulate and cause damage or become a breeding ground for bacteria and mold.
  2. Energy efficiency: Understanding condensate production can lead to insights on the system's efficiency and its cooling load.
  3. Maintenance planning: Anticipating the amount of condensate helps in scheduling maintenance and servicing of the unit.


Calculating FAHU condensate is a crucial aspect of HVAC system design and maintenance. By understanding the factors influencing condensate production and following a systematic approach, professionals can ensure the longevity and efficiency of their systems. Stay informed, and optimize your HVAC operations.

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