Cold Climate Evacuation Livestream - Pandora's Box · HVAC School - For Techs, By Techs summary

Key takeaways

Adding external heat is essential when evacuating systems in cold climates, as vacuum alone isn't sufficient to remove moisture.
The triple point of water (~4,580 microns) marks an important threshold; below this, moisture cannot exist as a liquid and sublimation becomes the only removal method.
Traditional evacuation techniques often fail in sub-zero conditions; therefore, new protocols incorporating heat provocation, dry ice, or nitrogen are necessary.
It’s critical to prevent moisture ingress during installation, especially in cold climates, to avoid complicated service scenarios later.
Understanding the physics—phase diagrams, Gibbs free energy, vapor pressure—helps technicians develop better strategies for low-temperature refrigeration work.
Industry education has historically overlooked fundamental science, but as cold climate systems become mainstream, these concepts must be integrated into best practices.

Summary

Introduction and Context of the Episode

This episode of HVAC School is a livestream focused on the challenging topic of refrigerant recovery and evacuation in cold climates. It features industry veterans Jim Bergmann, Roman Baugh, and Andrew Greaves discussing the real-world difficulties faced when working in sub-zero conditions, especially as cold climate heat pumps become more prevalent. The episode is motivated by stories of technicians encountering these challenges firsthand, and aims to provide a science-backed exploration of the issues and potential solutions.

The Rise of Cold Climate Heat Pumps and Their Impact on Service Procedures

The discussion begins with noting the increasing popularity of cold climate heat pumps, which operate efficiently at extremely low temperatures and are now primary heating sources in colder regions. This technological shift means that HVAC technicians are increasingly called upon to perform refrigeration repairs and evacuations in winter conditions where temperatures can drop below freezing, complicating standard procedures. The panel emphasizes that traditional installation and servicing practices are often inadequate for these conditions, leading to major challenges in refrigerant recovery and evacuation.

Physics of Moisture Removal and Vacuum Limitations in Cold Environments

A core part of the episode delves into the physics behind moisture removal from refrigeration systems, especially under low ambient temperatures. The guests discuss how water, in various phases, behaves when a deep vacuum is applied—particularly how sublimation becomes the only moisture removal process once the system's pressure falls below the triple point of water (~4,580 microns). They explain that at these depths, moisture can't exist as liquid and must turn directly from solid to vapor, a process that is hindered by lack of heat. Jim Bergmann demonstrates that pulling a strong vacuum on a wet system still leaves moisture in the system, illustrating the limitations of current techniques.

Innovative Techniques and Practical Solutions for Cold-Weather Evacuations

Andrew Greaves introduces the concept of a 'heat provocation test'—applying external heat to verify if moisture has been truly removed, based on micron gauge behavior. The panel discusses various practical methods such as using portable heaters, insulated tarps, belly bands, heat guns, and even dry ice traps to improve evacuation in cold conditions. They also explore temporary use of desiccant dryers and shell dryers with VRF systems as potential workarounds, emphasizing that adding heat remains the most effective strategy when service in cold weather is unavoidable.

Science of Moisture and Phase Changes in Refrigeration Systems

The hosts offer an in-depth look at the phase diagram of water, focusing on the triple point and how moisture behaves below it. Andrew explains how, at pressures below 4,500 microns, moisture can only be vapor or solid—never liquid—making sublimation the sole route for dehumidification at such low pressures. They discuss Gibbs free energy, phase transitions, and how sublimation can be hindered or accelerated depending on temperature and pressure conditions. The conversation underscores the importance of preventing moisture ingress from the start and highlights the challenges posed by the self-refrigerating cycle that occurs during deep vacuum pulls.

Recovery Challenges in Low Temperature Conditions and Best Practices

The panel emphasizes that refrigerant recovery in cold weather is difficult because the refrigerant and moisture both tend to freeze or become bonded at low temperatures, making complete recovery complex. Jim Bergmann stresses that the use of standard vacuum and recovery techniques often leaves significant quantities of refrigerant trapped. The discussion advocates for measures such as preheating components, using insulated covers, and doing pull-pull recovery strategies to maximize removal. They note that rapid industry growth in cold climate applications demands new protocols, including possible use of dry ice, nitrogen purging, and innovative recovery methods to stay compliant and protect equipment.

Show notes

In this long-awaited live episode of HVAC School, host Bryan Orr reunites with three industry veterans — Jim Bergmann of measureQuick, Roman Baugh (Kalos), and Andrew Greaves of NAVAC — to tackle one of the most pressing and underaddressed challenges in modern HVAC: performing refrigerant recovery and system evacuation in extreme cold-weather conditions. The conversation was sparked by a real-world observation from technician Chris Hughes, who relocated from Louisiana to Minnesota and quickly discovered just how different — and difficult — cold-climate HVAC work can be. What follows is an honest, science-heavy, and often humorous deep dive into a problem the industry has largely ignored.

The episode centers on the growing prevalence of cold-climate heat pumps, especially inverter-driven systems capable of operating at extremely low outdoor temperatures. As these systems become the primary heating source in cold regions, technicians are increasingly being called to make repairs — and perform evacuations — in sub-zero conditions. The group walks through why this is such a challenge, examining the fundamental physics that make pulling a proper vacuum nearly impossible once temperatures drop below 40°F. The conversation draws heavily from refrigeration science principles that, as Jim Bergmann bluntly points out, were largely left out of HVAC trade education over the past several decades.

One of the most compelling moments of the episode is Andrew Greaves' introduction of the "heat provocation test," a term he coins on the spot to describe a technique for verifying whether moisture has truly been removed from a system by observing micron gauge behavior after applying external heat to cold-soaked components. This sparks a rich debate between Jim and Andrew about where moisture actually concentrates in a system — in the line set vs. the outdoor unit — and whether heat can realistically reach those areas in a real-world installation. The panel ultimately agrees that heat is the only viable tool when you absolutely must complete a job in cold conditions, but that prevention and scheduling remain the gold standard.

The episode closes with a fascinating dive into the phase diagram of water, specifically the concept of the "triple point" and how it governs moisture behavior at low pressures. Andrew uses a whiteboard diagram to explain why, below 4,500 microns, moisture can only exist as vapor or solid — not liquid — and why that makes sublimation the only removal pathway when heat is absent. Jim adds nuance by describing the self-refrigerating cycle that occurs during deep vacuum pulls, a phenomenon that makes the problem progressively worse the deeper you pull without adding heat. The group wraps up with practical field takeaways and a promise to revisit the topic, including the potential role of nitrogen purging and triple-evacuation techniques in cold-weather scenarios.

Topics Covered

The rise of cold-climate heat pumps and why they demand refrigerant work during cold seasons
Why evacuation becomes extremely difficult — or impossible — below 40°F ambient temperature
The physics of moisture removal: heat energy, vapor pressure, and molecular movement
Jim Bergmann's real-world demonstration pulling a vacuum to 135 microns on a wet system and still failing the decay test
Andrew Greaves' "heat provocation test" — using external heat sources to verify dryness after evacuation
The debate over where moisture concentrates: outdoor unit vs. line set
Why mini-split manufacturers don't allow permanent desiccant dryers — and workarounds using temporary bypass configurations
VRF systems and how shell dryers can be temporarily added and then removed post-evacuation
The self-refrigerating cycle: how pulling a vacuum on ice makes the system progressively colder and more resistant to drying
Phase diagram of water: the triple point (~4,580 microns) and why liquid water becomes unstable below it
Why sublimation is the only moisture removal pathway below the triple point
Gibbs free energy and its role in determining which phase (solid, liquid, vapor) a substance will occupy
Hot nitrogen purging as a method for carrying moisture out of open line sets
Push-pull recovery technique to maximize refrigerant removal in cold conditions
The challenge of vapor recovery in cold weather — leaving multiple pounds of refrigerant behind
Practical field solutions: insulated tarps, portable propane heaters, belly band heaters, heat guns
Dry ice cold-trap brainstorm as a creative moisture capture method
The dual-fuel argument: why Jim advocates for backup heating as the real long-term solution
How rapid industry growth in the mid-20th century led to mechanics being trained instead of engineers, losing foundational science in the process
Why this topic matters more now than ever as cold-climate compression refrigeration becomes mainstream

You can watch the original livestream on YouTube HERE.

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Cold Climate Evacuation Livestream - Pandora's Box