R-Pro › Field cases › Refrigerators & showcases
New Refrigerants PT Chart — R-32 / R-454B / R-744 (CO2)
Likely causes
R-32 — single-component HFC, GWP 675, A2L (mildly flammable)
Check: Standard pressure at 35°C ambient cooling: high ≈3.3 MPa(g) → saturation 52°C; low ≈0.95 MPa(g) → saturation 5°C. About 5–10% higher than R-410A. Zero glide — use single-column PT. Discharge temperature ~10°C higher than R-410A.
What to do: 1) Use R-32-rated manifold (R-410A-compatible by pressure but digital manifold must select R-32 in menu). 2) A2L flammability rating — ventilate work area, no open flame. 3) Charge as liquid only, by weight. 4) On leak, do not top off — recover and replace with fresh refrigerant.
R-454B — HFO/HFC blend, GWP 466, A2L, ~1.5 K glide
Check: Direct R-410A replacement. Standard pressures nearly identical to R-410A (35°C ambient, high ≈3.0 MPa(g), low ≈0.85 MPa(g)). 1.5 K glide → PT chart has Bubble/Dew columns. Subcooling = use Bubble; superheat = use Dew.
What to do: 1) R-454B cannot be charged directly into an R-410A system — residual R-410A in hoses contaminates. Use dedicated manifold. 2) Glide refrigerant — liquid-phase only for charging/topping (vapor-phase charging causes composition shift). 3) On leak, recover and use fresh — no top-off. 4) A2L safety practices same as R-32.
R-744 (CO2) — natural refrigerant, transcritical cycle, very high pressure
Check: GWP 1, ODP 0 — best environmentally. Critical temp 31°C — above 25°C ambient runs transcritical → uses gas cooler instead of condenser, pressure 8–12 MPa (80–120 bar). Standard manifold unusable — needs dedicated ≥80 bar rated equipment. Spreading in supermarket refrigeration and automotive AC.
What to do: 1) CO2 work requires specific training/certification — standard refrigeration license insufficient. 2) Leak safety — CO2 itself non-toxic and non-flammable but mass leak causes asphyxiation in confined space (ventilate). 3) Evacuation uses micron gauge (same standard as other refrigerants). 4) Charging requires dedicated equipment rated ≥80 bar.
New refrigerants (R-32/R-454B/R-744) are spreading fast due to environmental regulations. Master the differences in pressure range, safety class, and required tools per refrigerant. Misuse leads to safety incidents and system damage.
All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.
Open R-Pro →Related cases
- Abnormal Superheat — Low / High Diagnosis
- Superheat Hunting — TXV Oscillation
- Superheat Cannot Be Measured — Gauge or Thermometer Reliability Failure
- Abnormal Subcooling — Low / High Diagnosis
- Zero Subcooling — Continuous Bubbles in Liquid Sight Glass
- PT Chart Usage — Pressure↔Temperature Conversion Diagnosis