Every since we had a Dampp-Chaser installation demo at our chapter meeting, I have been wondering about the theory behind its operation. When correcting for low humidity, the evaporation pad is heated to add moisture to the air. Then the moist air rises and bathes the soundboard with moist air - until the RH reaches 50%. Question 1: Although the soundboard is the primary target, how effective is this operation at raising the RH at the pin block? After the RH reaches 50%, the dehumidifier takes over. It doesn't remove any water from the air, but it raises the temperature of the air so that what water there is becomes a smaller percentage of what the air is capable of holding. A typical situation might be 80 degrees F and RH of 90% (a very humid summer day). If I understand the vapor tables correctly, it would take a temperature of 102 degrees F to make the 90% humidity come down to 45%. This is a 22 degree rise. Question 2: Is it possible for a Dampp-Chaser operating in dehumidify mode to keep the air around the soundboard 22 degrees higher than ambient? I'm sure the air immediately around the heating rod is hotter than this, but when that air diffuses with ambient air and reaches the edges of the soundboard, how hot can it be? If it is lower than 102 degrees, then the RH is higher than 45%. -Robert Scott Ann Arbor, Michigan
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