R-454B PT Chart

On the R-454B PT chart, a 40F bubble point corresponds to about 112 psig, where the dew point is 42.1F. At 260 psig the bubble point is 90F and the dew point is 92.4F. R-454B (Puron Advance) is a near-azeotropic A2L blend with only about 2F of glide, so its pressures sit close to R-410A but a hair lower.

R-454B is a zeotropic blend, so at any given pressure it boils and condenses across a small range of temperatures rather than at one point. The lower temperature is the bubble point and the higher one is the dew point; the gap is the glide, only about 2 degrees F for R-454B, which is why it is called a near-azeotrope. Because the glide is small, the two columns are close, but the table still lists both so you read the correct one.

Use the dew point for superheat and the bubble point for subcooling. Superheat is measured on the suction line where the refrigerant is fully vapor, which is the dew side. Subcooling is measured on the liquid line where it is fully liquid, which is the bubble side. R-454B's glide is only about 2F, so the penalty for reading the wrong column is small, but reading it right keeps the charge diagnosis clean.

Very close but not identical. R-454B runs a few psig below R-410A at the same temperature, which is why R-454B is a low-glide near-match on the pressure side and the R-410A line set is usually pressure-adequate. It is still not a drop-in: R-454B is A2L (mildly flammable), so it requires A2L-listed equipment, leak detection, and A2L service practices.