Just got a new place, didn't test the A/C during home inspection on account of it being too cold out (inspector said cold temps could damage outdoor compressor). Now it's getting hot, and I found out that there is extremely poor airflow to most of the second floor and some of the first floor/basement when running the A/C. It feels like there is the slightest amount of air wafting up through the floor registers, although it is cold air for sure. The exception is a single room on the second floor that receives extremely strong airflow (let's call this room 4).Relevant details:2 story home with basement, built 1994, unknown when basement finishedA/C is 4 ton outdoor unit with matched indoor furnace, furnace is located in the basementBasement looks like it was finished around existing ductwork - several vent lines are completely inaccessible behind drywall, and basement registers are fed from flexible linesVent splits in two directions (NE and SW). NE branch has very strong airflow on both first and second floor (Room 4). SW branch is externally wrapped with fiberglass, and has very poor airflow on second floor (Rooms 1-3 and 2 bathrooms).Some of the first floor vents blow air dramatically stronger than the others. I think these are the NE branch first floor vents.Suction at the return vents is very strong on the first floor and very poor on the second floor.Airflow in the basement vents (SW branch) is also very poor but at the moment I'm less concerned with those.What I've tried:Removing supply side (ugh) humidifier and visually inspecting the evaporator coil (no visible ice)Running the heat before switching to A/C (something about deicing?)Checking the squirrel cage blower for dirt and dust (virtually spotless)Adjusting airflow from 400-450 CFM/ton on the blowerClosing all dampers I could locate for the first floor ventsLooking for closed dampers for second floor vents (all are in open position, also tested by opening/closing)Temporarily blocking first floor ventsNothing seems to have worked and with the incoming summer heat I'm at my wit's end. Is this just a question of adding booster fans to the ductwork, since the little air that is received on the second floor is still cold? via /r/DIY http://ift.tt/2rppZCV
