What type of tubing is never used with ammonia?

Copper tubing is not used with ammonia due to the potential for a chemical reaction that can lead to the formation of copper salts. Ammonia, when in contact with copper or its alloys, can cause corrosion and degradation of the metal, compromising the integrity of the refrigeration system. This can lead to leaks and failure of the system, making copper a less suitable choice for ammonia refrigerant applications.

On the other hand, stainless steel tubing is commonly used due to its resistance to corrosion and ability to withstand the pressures involved in ammonia refrigeration systems. PVC tubing is also typically not used with ammonia because it can be affected by temperature and pressure, as well as the chemical properties of ammonia. Aluminum tubing may be used in some applications, but careful consideration is needed because aluminum can also corrode in the presence of ammonia. Overall, copper's reactivity with ammonia is the primary reason it is excluded from use in ammonia refrigeration systems.