I'm the guy with the appalling workmanship system and they are coming out to fix the problems on July 9th. I have a concern that the system may be oversized since it cycles on an off sometimes every 15 mins or so. The house gets down to the set temp but it still seems humid. A humidity gauge in the house was around 70% when the outside humidity was between 85-90%. I have a supply outlet going down to the finished basement but no return. If a return was added from the basement would that additional hot and humid air entering the system cause it to run longer and help with the possibility that the system is oversized.
The basement size was not included in the measurements the guy took to determine the system requirements. I'd also like to add another supply to the basement but that's another story.
Thanks again for your help.
The fan supplies and returns the exact same cfms,thru the equipment.
If you have a basement suppy and no return,the cfms going to the basement,may ay be pulled thru the windows,walls,attic,etc., to get back the the equipment.That's hot ,humid air.
Leave the door open to see if it makes a difference.To see/feel how much air it is ,crack the basement door ,with the system running.
If it's a gas furnace,BE Sure,combustion air for the furnace is addressed,when making changes in duct system.
Temperature, %RH of basement, region of US would help us comment. For comfort and controlling mold/dust mites maintain <50%RH inside your home. In green grass climates with +70^F outside dew points, a typical home needs 100 pints of moisture removal for <50%RH. With high cooling loads like 90^F outside your a/c removes 100 pints per day. At low load conditions like 75^F-85^F, your a/c does not run enough to remove large amounts of moisture. Consider a dehumidifier to provide <50%RH during cool wet conditions. Most residential dehumidifiers are inefficient, noisiy, and are low capacity at 50%RH. A 100 pint dehumidifier handles 2,500 sqft home. Suggest Ultra-Aire or Santa Fe from your a/c contractor.
Attempting to ,or correcting ,the OP's high humidity,with a dehumidifier,is masking the problem.
If after it's corrected ,or it's found to be oversized,and you'd rather buy a dehumidifier,then the correct size unit,then it's fine.
Do you have a VS blower.
If so, did they install a humidistat.
Theres only one real cure for an oversized system.
Have them check everthing while their there.
I live in Northern NJ and I do have a VS carrier airhandler.
I will have to ask if they installed a humidistat.
Thanks for your help.