HVAC drip line sweats during heavy AC use in summer
The problem could be the high humidity in the house. Here, north of Pittsburgh, Pa. I run a dehumidifier any time I am using the A/C unit to help reduce the humidity. Most A/C units are oversized not allowing the unit to run long enough to reduce the humidity. If you live in a high humidity area the A/C unit will not remove enough of the humidity in your house to allow you to feel comfortable. I set my dehumidifier at 40% and allow it to run automatically. I bought a GE unit rated at 70 pints per day from Sam's club and it keeps the humidity in check. One more thing, the drip line should have it's own trap close to the unit to keep cold air from blowing down the pipe causing the pipe to become cold which in turn coupled with a high humidity in the house causes it to swet. I would probably allow the condensate drain to run outside the house if that is legal in your area.