In this episode of the HVAC School podcast, host Bryan dives deep into the topic of vacuum in HVAC and refrigeration systems. He addresses two questions from social media about vacuum, expanding them into a comprehensive discussion of best practices, common issues, and techniques for effective vacuum procedures.

Bryan starts by explaining where to ideally locate a vacuum pump when working on a refrigeration system. He emphasizes the importance of pulling from the largest volume locations possible, often at multi-position service valves on the compressor or wherever accessible ports are available. He notes that systems that have been in operation pose unique challenges due to refrigerant dissolved in the oil, which can significantly increase vacuum time.

The podcast then covers the "one hose method" for pulling vacuum, detailing the process of using a single large hose connected to the suction side with the core removed, while placing the micron gauge on the liquid side. Bryan explains how this method can be highly effective for new systems but may take longer for systems that have been in operation. He also discusses the importance of valve quality.

Key topics covered in the podcast include:

• Ideal vacuum pump location in refrigeration systems
• The "one hose method" for pulling vacuum
• Challenges of vacuuming systems that have been in operation
• Using heat and nitrogen to improve vacuum efficiency
• Importance of quality valves and tools in vacuum procedures
• Proper maintenance of vacuum pumps and micron gauges
• Dealing with refrigerant dissolved in oil during vacuum
• The science behind evaporation at the oil-vapor interface
• Tips for speeding up vacuum in difficult conditions
• Recommended resources for further learning about vacuum techniques