Oil compatibility in ammonia refrigeration compressors

What’s the compatibility between polyol ester (POE) oils and naphthenic oils in ammonia (NH₃) refrigeration compressors?

There is sometimes confusion about compatibility between mineral naphthenic oils such as Mobil Gargoyle™ Arctic 300 and polyol ester oils like Mobil™ EAL Arctic series oils, as well as the performance of blends of these oils in the application.

The two oils are compatible. Although we recommend against the common practice of topping up Mobil EAL Arctic into Mobil Gargoyle Arctic 300 after switching a unit from R-22 to HFC blends like R-417a or R-422 in an existing unit. The application tolerates the mixture of oils because of hydrocarbons (butane) in the R-417a or R-422 HFC blends, which enhance the solubility of the refrigerant/oil mixture.

In some cases, the application is not suitable for the naphthenic/POE blend, because the performance of Mobil EAL Arctic is marginal with ammonia. So users should not add Mobil EAL Arctic to Mobil Gargoyle Arctic 300 in ammonia-based systems. The blend can create equipment performance problems due to the reaction of ammonia with certain Mobil EAL Arctic components.

If the above oils were blended, it is recommended to drain and flush the system, refilling with Mobil Gargoyle Arctic SHC™ 226E lubricant. The potential risk is some seal leakage due to shrinkage of the existing seals slightly due to the change from mineral naphthenic oil to this PAO-based lubricant.

Switching to Mobil Gargoyle Arctic SHC 226E lubricant is generally trouble-free. However, if leakage is detected, having a set of new seals on hand will allow for a quick fix.