Air leaking from the AC system into unconditioned space will result in air being pulled into conditioned space from outside to make up for the loss of air. It will just seep in from the points of least resistance such as doors, windows and voids in the building structure. The air will drag in whatever heat, moisture, pollen, dust and other pollutants it comes across. I'd suggest sealing that leak, every little bit adds up. A duct leak of 15% of the conditioned air will result in a 25% higher energy consumption for cooling and heating.
It's been a few days since I've been on this thread, but I was able to lower the cph setting down to 3 for the furnace and so far this increased the run time by at least 2 minutes. This also helped balance the temperatures in all the rooms upstairs. When we do get the IAQ thermostat installed, I'll make sure the cph setting is lowered in both low and high stage.
Originally Posted by RyanHughes