How to Diagnose Oil Return Problems Before They Damage a Compressor

Episode Overview In this episode of the HVAC Know It All Podcast, Host Gary McCreadie Director of Player Development and Head Coach at Shelburne Soccer Club and President of McCreadie HVAC & Refrigeration Services and HVAC Know It All Inc, examines compressor oil return, including why lubrication matters, how low load and reduced airflow affect oil movement, and how oil separators can protect compressors. Listeners will learn how to investigate oil-failure alarms, improve return velocity, and avoid replacing controls before finding the underlying system issue.

Drawing on a past five-story rooftop-unit service case and observations from LG VRF training, the host explains how improper building automation programming contributed to repeated compressor failures. That field perspective connects oil separators, inverter oil-return modes, suction piping, traps, double suction risers, and compressor unloading to practical troubleshooting decisions.

Key Takeaways Why inadequate lubrication can cause compressor seizure, metal debris, and component damage.

How an oil separator can return oil from the discharge line to the suction line without circulating as much oil through the system.

How reduced airflow and low suction pressure can prevent oil from returning to a compressor.

Why an oil-failure control trip requires troubleshooting oil pressure and return rather than immediately replacing the control.

How suction-line traps and double suction risers help maintain oil-return velocity in vertical piping.

The importance of periodically loading inverter or unloaded compressor capacity to bring pooled oil back to the compressor.

Key Timestamps: [00:00] - Sponsor: Factory Direct Filters

[02:32] - Why oil is important for compressor lubrication

[04:15] - How VRF oil-return mode raises compressor speed to return oil at low load.

[07:27] - Why an Oil Separator Was Recommended for the System