A technician mistakenly connects R-22 service gauges rated for a maximum working pressure of 350 psig to an R-410A system sitting in direct sun, where the liquid line temperature reads 130°F. If R-410A's saturation pressure at 130°F is approximately 401 psig, what is the primary safety concern?
- AThe gauge could be exceeded and rupture or leak, releasing refrigerant and risking injury since 401 psig exceeds the 350 psig rating
- BNothing, since gauges are universally rated for all refrigerant types
- CR-410A always operates at lower pressure than R-22, so no risk exists
- DThe system will automatically shut down before reaching that pressure
Show answer & explanationAnswer & explanation
Correct answer: A. The gauge could be exceeded and rupture or leak, releasing refrigerant and risking injury since 401 psig exceeds the 350 psig rating
R-410A operates at substantially higher pressures than R-22 (roughly 50–60% higher at equivalent temperatures) and requires gauges, hoses, and recovery equipment rated for higher working pressures. Connecting R-22-rated gauges (350 psig max) to a system reading 401 psig risks exceeding the gauge's rated limit, potentially causing rupture, refrigerant release, and injury to the technician.
Why the other options are wrong
- B. Gauges are refrigerant-specific due to differing pressure ranges and are not universally rated.
- C. R-410A consistently operates at higher pressure than R-22 at equivalent temperatures, the opposite of this claim.
- D. Gauges themselves do not have automatic shutoff features; system pressure switches are separate components.
R-410A vs R-22 Pressure Ratings
R-410A operates at significantly higher system pressures than R-22, requiring gauges, hoses, and recovery equipment specifically rated for its higher pressure range.
- R-410A pressures run roughly 50-60% higher than R-22 at the same temperature
- Using R-22-rated equipment on R-410A systems risks equipment failure
- Always verify equipment pressure ratings match the refrigerant in use
Memory trick: Match your gauge to the gas — mismatched pressure means glass could pass (burst).