Short #50 – Oil (Podcast)

In today’s short podcast episode, Bryan covers the basics of refrigerant oil in HVAC/R systems. He also discusses what technicians can do to maintain oil systems.

Oil lubricates the moving parts of the compressor. So, oil moves with the refrigerant and lubricates the parts as the refrigerant moves through the compressor. Unfortunately, oil can migrate to other parts of the circuit when it’s not supposed to.

Flooding occurs when liquid refrigerant enters the compressor crankcase, and slugging occurs when liquid gets into the compressor head. When either of those happens, they can eject oil from the system. When a system has insufficient oil, the compressor’s moving parts can heat up and wear out quickly. We can use an array of preventative strategies to keep oil in the system and reduce the risk of compressor damage.

We want to keep our discharge lines below 225 degrees to prevent oil (or lubricant) breakdown. To prevent the compressor from overheating, we want to look at mass flow rates and compression ratios. We should also make cleanliness a priority, as dirty components can increase the compression ratio.

Oil has evolved with refrigerants. We largely used mineral oil with HCFCs like R-22, but we have begun using POE oil with HFC refrigerants like R-410a. Newer HFCs are generally NOT miscible with mineral oil, but we must be careful with POE and PVE refrigerants because they are hygroscopic. These oils break down via hydrolysis when they react with moisture, and they become acidic. So, we need to keep POE and PVE systems dry to prevent damage.

Bryan also covers:

• Hard shut off TXVs
• Pump down cycles
• Oil return
• Viscosity
• Oil velocity and pipe design
• Miscibility
• AB oil

Check out our oil article HERE.

Learn more about Refrigeration Technologies HERE.

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