How marine A/C works
This may help explain marine A/C systems.
Air conditioners don’t really produce cold, they remove heat. As the phase-converting refrigerant passes through the evaporator coils, it gets colder but more gaseous (because it’s boiling), and absorbs heat from the surrounding air. A fan blows warm air from the cabin across the evaporator and discharges it, now cooler, through ducting back into the cabin. The evaporator/fan/ducting assembly is called an “air handler.” The warm air that’s pulled in from the cabin is called “return” air, while the “supply” air is the cold air coming out of the air handler.
Pressure equals heat, so to cool the gas on the downstream side of the compressor it’s run through a raw-water-cooled condenser, which returns the refrigerant to a liquid state. The colder the water, the more efficient the cooling, but most air conditioners will work fine to water temps into the 80-degree range, sometimes warmer. Then the refrigerant returns to the expansion valve and the cycle begins again.
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Captain F. Lee - R.P.E.
USCG 200 GT Master
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