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We are entering the second summer in our house and I'm starting to wonder if our AC unit is undersized. Usually we try to not let the house get too warm in the first place by keeping the shades down and turning the air conditioning on in the late morning when the house is about 70 degrees. In order to keep the house at 70 though the unit seems to run continuously. Recently we had a family gathering and with lots of people in the house we couldn't get the temperature down from 74.
As stated in the title the unit is a Trane XR12 (build date 1/2003) 1.5 ton as verified by dividing the 7th and 8th digits of the model number (18) by 12. The house is a simple rectangular ranch, about 1100 square feet with 8 foot ceilings, 2x4 walls with fiberglass insulation (no idea on the R-rating), 6" of fiberglass insulation in the ceilings, fairly new vinyl windows, one picture window with a wooden frame that's a bit drafty, and three exterior doors that are a bit drafty. The house was built in the mid-60s with forced air oil heat so the AC uses the existing ductwork. The coil sits at one end of the house and feeds into the trunkline which runs the length of the house (about 45 feet) with 6" delivery ducts branching off. We have attic fans but ventilating the roof doesn't seem to help. To address the obvious we change the filter religiously every 30 days due to allergies. Finally, the rear of the house faces directly south. There are only 3 south facing windows, but we don't have any shade so the rear roof (simple a-frame) and rear wall get a lot of sun. So, given all of that, does it sound like my unit is undersized? If so, how much will it help to tighten up the house, add insulation, etc...?
As stated in the title the unit is a Trane XR12 (build date 1/2003) 1.5 ton as verified by dividing the 7th and 8th digits of the model number (18) by 12. The house is a simple rectangular ranch, about 1100 square feet with 8 foot ceilings, 2x4 walls with fiberglass insulation (no idea on the R-rating), 6" of fiberglass insulation in the ceilings, fairly new vinyl windows, one picture window with a wooden frame that's a bit drafty, and three exterior doors that are a bit drafty. The house was built in the mid-60s with forced air oil heat so the AC uses the existing ductwork. The coil sits at one end of the house and feeds into the trunkline which runs the length of the house (about 45 feet) with 6" delivery ducts branching off. We have attic fans but ventilating the roof doesn't seem to help. To address the obvious we change the filter religiously every 30 days due to allergies. Finally, the rear of the house faces directly south. There are only 3 south facing windows, but we don't have any shade so the rear roof (simple a-frame) and rear wall get a lot of sun. So, given all of that, does it sound like my unit is undersized? If so, how much will it help to tighten up the house, add insulation, etc...?