Why a bigger AC is not better — oversizing short-cycles and leaves the house cold but clammy
Bigger is not better. An oversized AC short-cycles: it cools fast but never runs long enough to dehumidify, so you get a cold, clammy house plus extra compressor wear. A right-sized unit (ACCA Manual S: 95–115% of the load) runs long, steady cycles that stay cool AND dry.
What this diagram shows
A wrong-versus-right comparison of air-conditioner sizing. On the left, an oversized system (more than 115% of the calculated load) runs in short bursts — on, off, on, off — hitting the thermostat quickly but never running long enough to pull moisture out of the air, so the house is cold but clammy, the compressor wears from stop-start, and rooms are uneven. On the right, a right-sized system (95 to 115% of the load per ACCA Manual S) runs long, steady cycles that hold both temperature and humidity, so the house is cool and dry and the equipment lasts. Size to the calculated load, not the next size up.
HVAC BTU / Manual J Calculator
Cooling + heating BTU, AC tonnage, furnace size, heat-pump balance point — per ACCA Manual J / S, ASHRAE 1%/99%. DOE 2023 SEER2. Free.
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