Oils

Owing to the particularly high solubility of R290 and R1270 in conventional oils, the BITZER compressors for R290/R1270 are charged with a special oil that has a high viscosity index and particularly good tribological properties.

For the reciprocating compressors, there are two different oil types to choose from. The PAG oil is recommended for compact circuits.

With regard to solubility, there are special requirements for the design, operating mode and control of the compressor and system. Low or insufficient superheat in operation and insufficient heating of the oil sump during standstill periods lead to a substantial reduction of the oil viscosity in the compressor. This results in reduced performance, heavy wear on drive gear parts, increased oil carry over and foaming. Secure compressor against ''wet operation'' and guarantee a sufficiently high suction gas temperature − for reciprocating compressors, the discharge gas temperature must be at least 20 K and for compact screw compressors 30 K above the condensing temperature!

• Low oil temperatures and a high suction-side standstill pressure must be avoided and an oil heater is absolutely required and, if necessary, an additional pump down system must be provided.
• Avoid quick changes in suction pressure − risk of inadequate lubrication due to strong outgassing of the refrigerant from the oil and unstable suction gas superheat.
• Avoid quick changes in condensing pressure − risk of considerable foaming in the oil separator! When using a 4-way reversing valve, for example in heat pumps, the valve must only be switched when the compressor is not in operation. Switching it during compressor operation leads to strong pressure fluctuations, which have a negative effect on the lubricity of the oil used. Check all operating conditions to ensure that they are safe!