Fillable Printable 404A Pressure Temperature Sample Chart
Fillable Printable 404A Pressure Temperature Sample Chart
404A Pressure Temperature Sample Chart
°F R‐404A
‐50 0.6
‐45 2.7
‐40 5
‐35 7.6
‐30 10.4
‐25 13.4
‐20 16.8
‐15 20.5
‐10 24.5
‐5 28.8
0 33.5
5 38.6
10 44
15 49.9
20 56.2
25 63
30 70.3
35 78.1
40 86.4 SYSTEM PROBLEM DISCH PRESS SUCT PRESS SUPERHEAT SUBCOOLING AMP DRAW
45 95.2 OVERCHARGE HIGH \ \ HIGH HIGH
50 104.7 UNDERCHARGE \ LOW HIGH \ \
55 114.7 LIQUID RESTRICT. \ LOW HIGH \ LOW
60 125.3 LOW EVAP FLOW \ LOW LOW \ \
65 136.6 DIRTY CONDENSER HIGH \ \ \ HIGH
70 148.6 LOW AMBIENT °F LOW LOW HIGH HIGH \
75 161.2 TXV BULB BAD \ LOW HIGH \ \
80 174.6
85 188.8
90 203.7
95 219.4
100 235.9
105 253.4
110 271.7
115 290.9
120 311.1
125 332.3
130 354.5
135 377.8
140 402.2
145 427.7
150 454.4
Subcooling is determined by taking the high side pressure gauge reading, converting that
pressure to temperature using a PT chart, and then subtracting that temperature from
the actual temperature measured (using an accurate thermometer or thermocouple) at
the same point the pressure was taken.
404A PRESSURE‐TEMPERATURE CHART
REFRIGERATION SYSTEM ANALYSIS
WHAT IS SUPERHEAT & SUBCOOLING AND HOW TO MEASURE IT
Superheat refers to the number of degrees a vapor is above its saturation temperature
(boiling point) at a particular pressure.
Superheat is determined by taking the low side pressure gauge reading, converting that
pressure to temperature using a PT chart, and then subtracting that temperature from
the actual temperature measured (using an accurate thermometer or thermocouple) at
the same point the pressure was taken.
Subcooling is the condition where the liquid refrigerant is colder than the minimum
temperature (saturation temperature) required to keep it from boiling and, hence,
change from the liquid to a gas phase.
