R717 (ammonia)
Also known as: ammonia, NH₃, R-717
Short definitionAmmonia. A natural refrigerant with no greenhouse effect and very high efficiency; because it is toxic and mildly flammable (B2L), it needs a separate machine room and trained operating staff.
When a quotation is requested for a meat plant or a large logistics store, ammonia comes onto the table. Its latent heat is high, so little refrigerant circulates and the compressor runs efficiently. It is cheap and harms neither the ozone layer nor the climate. Its sharp smell gives a leak away at once. Dairies, ice rinks and blast freezing tunnels run on ammonia for the same reasons.
It is not specified for small and medium rooms, because the investment and the operating requirements are heavy. The pipework is steel or stainless steel; copper is not used. The machine room is separate from the cooled space; cooling is carried to the rooms by glycol, by CO₂ or by a pumped circuit. Gas detection and emergency ventilation are mandatory: the smell is noticed at 25 ppm and anything above 300 ppm is dangerous. In plants above 500 kW that run continuously it is usually the most economical choice.