Okay, everyone I have some further research today it got above 90 degrees outside which brings on the condensation problems on the outside of the ducts.
The outside of the plenum is still condensing , and the branch off the plenum (zone) that goes up a unconditioned flu chase up to the attic (for the upstairs heating/cooling) is dripping water down the chase off the ducts.
But there seems to be a much bigger problem. These sheet metal ducts going up the flu chase are not insulated in any way. This flu chase leads up to the attic. The stud walls of the flu chase are insulated with R-22 and R-13 on one side but it is not conditioned air in this flu chase. There is water dripping down the ducts from the flu chase I can see it with a flash light looking up from the mechanical room. That is the main problem is that this water dripping out the flu cahse is leaving a large pool of water on the floor of the mechanical room. Also the plenum and the whole branch coming off the plenum is condensing, but not as bad as the flu chase
All ducts in this entire branch going up the flu chase into the attic are uninsulated according to contractor. Earlier this summer the contractors went into the attic and put fiberglass insulation on the big box in the attic that has insulated flex ducts leading off it. Before this big box only had blown attic insulation covering it and they thought that was the problem. Supposedly they also made sure that where the flu chase ducts and the attic meets, is a tight seal now. The manager also told me the contractor that installed everything last year is no longer with the company.
I did what you guys suggested and bought a hygrometer today. Relative Humidity in the mechanical room is 65 with a dehumidifier turned off today, at a temperature in the mechacial room of 70 degrees.
I am feeling like yes maybe the dehumidifier will help the mechanical room I guess if I run it 24/7, but should I really be expected to do this? Also I wondering with the flu chase dripping problems coming to light I don't think there is anyway to dehumidify up in there for two stories.
Thanks for you help everyone. In my opinion does it seem like the plenum, all the way up the zone branch that leads into the attic through the flu chase, should have been insulated?
What type of easy fixes is there? or basically does someone need to tear the sheetrock walls up and tear out that entire branch and start over with insulated ductwork?
Thanks again everyone for your expert help.