Refrigerant Identification, Properties and Environmental Impact
What you must be able to do
Identify refrigerants by number, by family and by their environmental characteristics. Know the ASHRAE numbering: R-134a is an HFC, R-410A is an HFC blend (R-32/R-125, near-azeotropic), R-407C is a zeotropic HFC blend with temperature glide, R-22 is an HCFC, R-12 is a CFC, and R-744 is carbon dioxide. Recognise that 'azeotropic' means negligible glide and 'zeotropic' means a glide across the evaporator, which affects charging method - liquid charging for zeotropes.
Environmental metrics
- ODP (ozone depletion potential): CFCs high, HCFCs low but non-zero, HFCs zero.
- GWP (global warming potential): referenced to CO2 over 100 years. R-134a ≈ 1430, R-410A ≈ 2088, R-32 ≈ 675, R-744 = 1.
- Atmospheric lifetime and flammability class (A1, A2L, A3) matter for safety and for the phase-down.
Traps
Questions often test the difference between ODP and GWP - an HFC has zero ODP but significant GWP, which is why it is still regulated. Another trap is confusing R-410A and R-32 GWPs, or assuming a blend behaves like a single substance when charging. Zeotropic blends must not be charged as vapour, and a leaking blend can fractionate, changing composition.
Rule of thumb
CO2e = mass (kg) × GWP ÷ 1000, giving tonnes. Use it to compare the climate impact of two refrigerants: replacing R-410A with R-32 cuts the GWP by roughly two-thirds for the same charge. Always state units in your answer.