Natural gas is burned to heat a water and ammonia mixture, evaporating the ammonia from the water and condensing it outside the home. This ammonia is then decompressed and evaporated around a circulating water system, cooling the water. The water circulates through piping and thus cools the home.
Most natural-gas-powered air conditioning units for homes are classified as small, direct-fired absorption chillers and use ammonia and water as components. Both these components are environmentally safe. These units use ammonia as the refrigerant while water is the absorbent. In general, absorption units work through the condensation of the refrigerant, which removes heat from the absorbent. This method of air conditioning is perfect for homes with baseboard heating, and does not require duct work to operate.
The whole unit works in a cycle, with the beginning and end products of the reaction both being a mixture of ammonia and water. Initially, the mixture is heated by natural gas and ammonia condenses outside the home in a coil. The ammonia then cools a circulating water system through evaporation at a low pressure. This water system circulates through the home and cools it. After the ammonia evaporates, it is reabsorbed into the water source and then process repeats over again.