CSLB C-20 HVAC ContractorCooling and RefrigerationEasy
A technician is recovering refrigerant from a residential system into a DOT-approved recovery cylinder. To prevent hydrostatic overpressure and cylinder rupture, filling should stop at approximately what percentage of the cylinder's rated weight capacity?
- A100%
- B80%
- C90%
- D60%
Show answer & explanationAnswer & explanation
Correct answer: B. 80%
DOT regulations and industry standards require recovery cylinders to be filled to no more than 80% of their rated capacity by weight, leaving vapor space for thermal expansion of the liquid refrigerant and preventing hydrostatic rupture.
Why the other options are wrong
- A. Filling to 100% leaves no room for liquid expansion and risks rupture.
- C. 90% still exceeds the safe margin required for thermal expansion.
- D. 60% is overly conservative and not the standard industry limit.
Recovery Cylinder 80% Rule
Recovery cylinders must never be filled beyond 80% of their rated weight capacity to allow for liquid thermal expansion and prevent overpressure rupture.
- Applies to all DOT-approved refrigerant recovery cylinders
- Leaves 20% vapor space for expansion
- Overfilling can cause dangerous hydrostatic pressure buildup
Memory trick: Eighty percent, no more — leave room, or it'll roar.