I have noticed in my attic the galvanized 'stuff' seems to be rusting. Today i was up there looking at another problem and noticed the plenum..or whatever it is the duct lines come out of, was sweating...a lot. It runs off the side, onto some of the flexible duct and then drips onto the attic floor, causing it to stay damp and its black with mold and mildew. I have scheduled service, but what is the acceptable repair for this? This system is less than 10 years old, and there are parts that are 'crunchy' with rust underneath the mastic. Its a heat pump unit with a variable speed compressor and handler. It runs...a LOT. IM in texas, and the unit outside usually doesnt spend more than 1 minute off, unless its night time. Its usually on the low setting, but between the zones, it runs a bunch.
Any ideas on the sweating? Aside from that the system cools fantastic.