Arkansas HVACR NewsMagazine January 2026

HVACR NewsMagazine January 2026

Tech News

the ice rapidly, nor does it mechanically dislodge it.

Sublimation is the direct transition from solid to vapor, skipping the liquid phase. This process requires a massive input of energy: the latent heat of sublimation. For water ice, that’s approximately 2.8 MJ/kg. ⁷ In a vacuum, there is no convective heat transfer from the air (because there is no air). The only source of heat is conduction from the copper tubing and the remaining internal energy of the ice itself.

5. Why Triple Evacuation Was Never Designed for Today’s Systems

6. What Actually Works Better Than Triple Evacuation

Triple evacuation was developed for:

Single-stage pumps with roughly 300 micron ultimate vacuum

• 1/4 ″ hoses that choked in molecular flow ⁴ • Compound gauges that couldn’t verify below 200 microns • Dirtier systems before nitrogen-swept copper became standard Two-stage pumps rated at 25 microns • High-flow vacuum rigs (TruBlu, etc.) that maintain conductance ⁵ • Digital micron gauges with decay graphing • Nitrogen that isn’t perfectly dry (3 -5 ppm moisture in most cylinders) ⁶ But the real reason triple evac fails in cold weather is simple: • Moisture is frozen, and nitrogen cannot melt or remove ice. • Cold systems dry by sublimation, not boiling, which is extremely slow. You cannot sweep a solid. Blowing dry gas over an ice cube in a copper pipe is incredibly inefficient compared to sublimating it. The nitrogen does not transfer enough heat to melt Modern reality: •

To dry a system, especially in cold weather, you need: • ONE long, deep pull (<200 microns) Not three shallow ones. • TIME Sublimation has no shortcuts. • HEAT (even a little helps)