An uninsulated supply tap is sweating and dripping
Cold supply metal exposed to humid plenum air can sweat. Dry it, verify insulation/vapor barrier requirements, and wrap/seal it so humid air cannot reach the cold metal.
Check nearby diffusers, boots, and seams for more sweating.
Say this to your foreman
The supply tap at [location] is sweating and dripping. I dried the metal and checked missing insulation/vapor barrier. Do you want it wrapped/sealed per the insulation spec and nearby cold surfaces checked too?