Question 1

What is a PT chart?

Accepted Answer

A PT chart (pressure-temperature chart) shows the relationship between saturation pressure and temperature for a refrigerant. At any given temperature, the chart tells you the exact pressure at which the refrigerant boils (changes from liquid to vapor). HVAC technicians use PT charts to diagnose system performance and verify proper charge.

Question 2

What is the pressure of R-410A at 70°F?

Accepted Answer

R-410A has a saturation pressure of approximately 201.7 PSIG (216.4 PSIA) at 70°F. This is significantly higher than R-22, which operates at about 121.4 PSIG at the same temperature.

Question 3

What is replacing R-410A?

Accepted Answer

R-454B is the primary replacement for R-410A in residential AC and heat pump systems. Since January 2025, all new equipment in the US must use R-454B or another approved low-GWP alternative. R-454B has a GWP of 466 compared to R-410A's 2088 — a 76% reduction. Existing R-410A systems can continue to be serviced with R-410A.

Question 4

What is superheat and subcooling?

Accepted Answer

Superheat is the temperature of refrigerant vapor above its saturation temperature at a given pressure. It confirms all liquid has evaporated before reaching the compressor. Target: 8-15°F. Subcooling is the temperature below saturation at the condenser outlet, confirming all vapor has condensed. Target: 10-18°F for TXV systems.

Question 5

Is R-22 still available?

Accepted Answer

R-22 (Freon) production and import was banned in the US in 2020 under the Clean Air Act. It is only available as reclaimed or recycled refrigerant for servicing existing systems. New equipment has not used R-22 since 2010. The most common replacements are R-407C (drop-in retrofit) or R-410A (new systems).

Temp	PSIG	PSIA	kPa
0°F	48.4	63.13	435.3
10°F	62.4	77.13	531.8
20°F	78.7	93.36	643.7
30°F	97.4	112.07	772.7
35°F	107.7	122.43	844.1
40°F	118.8	133.49	920.4
45°F	130.6	145.28	1001.7
50°F	143.1	157.84	1088.3
55°F	156.5	171.21	1180.4
60°F	170.7	185.4	1278.3
65°F	185.8	200.47	1382.2
70°F	201.7	216.43	1492.2
75°F	218.6	233.33	1608.8
80°F	236.5	251.21	1732.0
90°F	275.3	290.03	1999.7
100°F	318.5	333.23	2297.5
110°F	366.5	381.15	2627.9
120°F	419.5	434.17	2993.5
130°F	478.0	492.73	3397.2
140°F	542.6	557.33	3842.6
150°F	613.9	628.59	4334.0

Refrigerant PT Charts

Popular Refrigerants

R-410A

R-22

R-134a

R-454B

R-404A

R-407C

R-32

R-290 (Propane)

R-717 (Ammonia)

R-744 (CO₂)

R-1234yf

R-507A

R-410A Quick Reference

R-454B — The New Standard