Humidity, and why bigger is worse in Mobile
冷氣度日 1662、平均濕度 75%——機組要同時降溫與除濕，**選太大反而更潮濕**（跑太短、來不及把水抽掉）; 屋齡中位 1975 年——那個年代的風管與絕緣多半跟不上現在的機組效率，換機前值得先看風管.
冷氣度日 1662、平均濕度 75%——機組要同時降溫與除濕，**選太大反而更潮濕**（跑太短、來不及把水抽掉）
屋齡中位 1975 年——那個年代的風管與絕緣多半跟不上現在的機組效率，換機前值得先看風管
Average relative humidity around Mobile sits near 75 percent, which decides whether the machine's job is mostly cooling or mostly pulling water out of the air.
Why this changes what you should buy
A cooling system does two jobs: it lowers the temperature and it removes water from the air. Those two jobs compete. Removing water takes time on the coil, and a system that satisfies the thermostat quickly never gets that time. In a humid climate the comfortable house is the one whose system runs longer, not the one whose system is bigger.
Mobile runs about 1662 cooling degree days a year, which is a direct proxy for how many hours the compressor will actually turn - and compressors wear out by running hours, not by calendar years.
What to ask for, in order
- A Manual J load calculation, not a square-footage rule of thumb
- A system sized to that calculation, even if it is smaller than the one being replaced
- A variable-speed or two-stage compressor if the budget allows - it runs longer at lower output, which is exactly what removes moisture
- Duct inspection before sizing, because leaking ducts change the answer
Mobile gets roughly 52 days a year above 32 Celsius, and those are the days a system that is even slightly undersized will never catch up.
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