The refrigerant R717 is a natural refrigerant just like R290 and is better known as ammonia.

150 years after the first discovery of ammonia as a refrigerant in cooling processes, the highly efficient substance might make its strong reentry in the heating industry. Despite the general belief that ammonia would be limited to large refrigeration processes, R717 would be similarly efficient in large-scale heat pumps.

Compressors that could handle the pressure requirements of ammonia, in the past often not available in the right size or only at higher costs, are now offered. Moreover, these high-pressure compressors with balanced radial and axial forces would ensure a high durability needed for large-scale heating systems. The limits of using R717 could range as widely as from process heating at + 90°C to process cooling at -40°C.