Steven: In addition to what David said, duct leakage in the supply ducts can cause condensation problems. When cold air leaks into the duct insulation, it can lower the surface temperature of the outer jacket, which can lead to condensation. Duct sealing is the solution. Another issue that causes condensation is when two ducts are rubbing up against each other. Separating the ducts is the solution. And burying ducts in attic insulation in Florida can lead to condensation. Here’s what I wrote about that:

Buried Ducts Risk Condensation in Humid Climates

@steven, I’m assuming by ‘similar problem’ you mean condensation on ducts. The two most likely causes for that are low airflow and problems with the supply-side duct insulation, especially for locations close to the air handler where supply air is coldest.

Insulation problems are common, including exposed bare metal and/or insulation jacket poorly sealed.

Inadequate airflow (relative to A/C capacity) is also a very common problem. This causes the supply air to be too cold, which contrary to what one might expect, actually *reduces* an air conditioner’s ability to cool the air. Low airflow can be caused by any or all of the following conditions: (a) improper blower speed setting, (b) inadequately sized ducts (i.e., too small), (c) as a crushed or pinched duct, and/or (d) the filter is dirty or overly restrictive.

Most of these problems can be diagnosed and remedied by a smart HVAC technician. I recommend looking for “NATE certification” when selecting a mechanical contractor to diagnose airside problems.