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summary: replaced 2 carrier seer 12 with 2 lennox seer 17 & 18.6 with 2 spd compressor & var. spd air handler. ducts, which never sweat before, now are dripping from the bottom of the supply trunk in the attic... and the sheetrock under the soffit in the garage containing the supply trunk for the first floor was dripping. trunks are round metal wrapped with fiberglass, taped and mastic.

Contractor says reinsulate ducts. Forgot to mention, old air handlers were 4 ton, new are 3 ton. I shut off humidity control and set fan delay to 100% on then 60 second shutdown.

Now garage ceiling has dried except for one spot and attic dripping SEEMS to have lessened.

upstairs lennox model HPXA19-036
fan setting=1400, SEER 17

downstairs lennox model HPXA19-038
fan setting=1275, SEER 18.6

Air handlers are both CBX32MV-036

what is proper cfm per ton (heard range of 400-450)
what is effect of increasing cfm?
what is upper limit you should set cfm for cooling or heating?
docs are not clear which has preference: stage one cooling fan speed at 70%, or delay setting of 100%....anyone know?
finally: what is proper temp diff from return to supply?

Does Lennox have a problem with my equipment they are not disclosing? Factory refers back to contractor. Contractor has set up visit from factory rep next week, but has not responded to request for conference call with factory engineers.

I am located at the beach in SC, high temp and humid, but ducts never had condensation with carriers.

Thanks for any help or suggestions.