Prevent Condensation From Becoming A Design Flaw

Water condensation is easily the most common concern when discussing chilled beams and cooling panels. This concern comes from the personal experience many have had seeing water droplets form on the surface of piping such as a water coil.

When condensate forms it is too late to prevent the surface from becoming wet. The question, however, is how to prevent condensate from becoming a design flaw in the building.

The HVAC designer needs to verify that the ventilation system is capable of handling the latent load. Humidity loads that need to be addressed include:

  • Ventilation Load: Generally the largest moisture load.
  • Infiltration Load: Moisture that crosses the building shell.
  • Occupant Load: As people breathe and perspire, moisture is released into the space.
  • Other Loads: Fountains, doors and windows left open, wet clothing, etc.

To provide control of the air dew point and supply water temperature, several different control strategies are often used.

  • Monitor the local dew point temperature.
  • Monitor condensate on the chilled water supply (CHWS) piping.
  • Reset the CHWS temperature based on outdoor conditions.

Often, a combination of these control strategies is used. Other considerations are the type of fresh air systems (DOAS), system response time, building start up, night setback and recovery after high humidity levels in the interior space.

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