NH3 Pressure-Temperature Chart
Saturation curve for anhydrous ammonia (R-717) — ASHRAE 2017 / NIST data.
Data: ASHRAE Fundamentals 2017 · NIST Webbook · R-717 (NH₃)
Superheat / Subcooling Calculator
Superheat = refrigerant vapor temperature above saturation at a given pressure (suction line). Subcooling = liquid temperature below saturation at a given pressure (liquid line). Both are measured in °F or °C above/below the saturation point.
| Temp (°F) | Temp (°C) | psia | psig | kPa abs | ρ_L (lb/ft³) | ρ_V (lb/ft³) | h_L (BTU/lb) | h_V (BTU/lb) | h_fg (BTU/lb) |
|---|---|---|---|---|---|---|---|---|---|
| -60 | -51.1 | 5.55 | -9.15 | 38.3 | 44.37 | 0.0242 | -21.2 | 589.6 | 610.8 |
| -55 | -48.3 | 6.54 | -8.16 | 45.1 | 44.06 | 0.0282 | -15.9 | 591.4 | 607.3 |
| -50 | -45.6 | 7.67 | -7.03 | 52.9 | 43.75 | 0.0326 | -10.7 | 593.1 | 603.8 |
| -45 | -42.8 | 8.95 | -5.75 | 61.7 | 43.44 | 0.0376 | -5.4 | 594.9 | 600.3 |
| -40 | -40.0 | 10.41 | -4.29 | 71.8 | 43.13 | 0.0432 | 0.0 | 597.6 | 597.6 |
| -35 | -37.2 | 12.05 | -2.65 | 83.1 | 42.81 | 0.0495 | 5.4 | 599.5 | 594.1 |
| -30 | -34.4 | 13.90 | -0.80 | 95.8 | 42.49 | 0.0565 | 10.7 | 601.4 | 590.7 |
| -28NBP | -33.3 | 14.70 | 0.00 | 101.4 | 42.36 | 0.0596 | 12.6 | 602.1 | 589.5 |
| -25 | -31.7 | 15.98 | 1.28 | 110.2 | 42.16 | 0.0643 | 16.2 | 603.3 | 587.1 |
| -20 | -28.9 | 18.30 | 3.60 | 126.2 | 41.83 | 0.0728 | 21.4 | 605.2 | 583.8 |
| -15 | -26.1 | 20.88 | 6.18 | 144.0 | 41.50 | 0.0822 | 26.7 | 607.1 | 580.4 |
| -10 | -23.3 | 23.74 | 9.04 | 163.7 | 41.17 | 0.0927 | 32.1 | 608.9 | 576.8 |
| -5 | -20.6 | 26.92 | 12.22 | 185.6 | 40.83 | 0.1043 | 37.5 | 610.8 | 573.3 |
| 0 | -17.8 | 30.42 | 15.72 | 209.7 | 40.49 | 0.1170 | 42.9 | 612.6 | 569.7 |
| 5 | -15.0 | 34.27 | 19.57 | 236.3 | 40.14 | 0.1310 | 48.4 | 614.4 | 566.0 |
| 10 | -12.2 | 38.51 | 23.81 | 265.5 | 39.79 | 0.1450 | 53.8 | 616.2 | 562.4 |
| 15 | -9.4 | 43.14 | 28.44 | 297.4 | 39.43 | 0.1610 | 59.4 | 617.9 | 558.5 |
| 20 | -6.7 | 48.21 | 33.51 | 332.4 | 39.08 | 0.1780 | 64.7 | 619.8 | 555.1 |
| 25 | -3.9 | 53.73 | 39.03 | 370.5 | 38.71 | 0.1970 | 70.2 | 621.5 | 551.3 |
| 30 | -1.1 | 59.74 | 45.04 | 411.9 | 38.34 | 0.2170 | 75.7 | 623.2 | 547.5 |
| 35 | 1.7 | 66.26 | 51.56 | 456.8 | 37.96 | 0.2390 | 81.3 | 624.9 | 543.6 |
| 40 | 4.4 | 73.32 | 58.62 | 505.5 | 37.58 | 0.2620 | 86.8 | 626.5 | 539.7 |
| 45 | 7.2 | 80.96 | 66.26 | 558.2 | 37.19 | 0.2880 | 92.4 | 628.1 | 535.7 |
| 50 | 10.0 | 89.19 | 74.49 | 614.9 | 36.80 | 0.3150 | 97.9 | 629.7 | 531.8 |
| 55 | 12.8 | 98.05 | 83.35 | 676.0 | 36.40 | 0.3440 | 103.6 | 631.2 | 527.6 |
| 60 | 15.6 | 107.60 | 92.90 | 741.9 | 36.00 | 0.3750 | 109.2 | 632.7 | 523.5 |
| 65 | 18.3 | 117.80 | 103.10 | 812.2 | 35.59 | 0.4080 | 114.9 | 634.2 | 519.3 |
| 70 | 21.1 | 128.80 | 114.10 | 888.0 | 35.18 | 0.4440 | 120.5 | 635.6 | 515.1 |
| 75 | 23.9 | 140.50 | 125.80 | 968.7 | 34.75 | 0.4810 | 126.3 | 636.9 | 510.6 |
| 80 | 26.7 | 153.00 | 138.30 | 1054.9 | 34.32 | 0.5220 | 131.9 | 638.3 | 506.4 |
| 85 | 29.4 | 166.40 | 151.70 | 1147.3 | 33.88 | 0.5650 | 137.7 | 639.5 | 501.8 |
| 90 | 32.2 | 180.60 | 165.90 | 1245.2 | 33.43 | 0.6110 | 143.5 | 640.7 | 497.2 |
| 95 | 35.0 | 195.80 | 181.10 | 1350.0 | 32.97 | 0.6600 | 149.4 | 641.8 | 492.4 |
| 100 | 37.8 | 211.90 | 197.20 | 1461.0 | 32.51 | 0.7130 | 155.2 | 642.9 | 487.7 |
| 105 | 40.6 | 229.00 | 214.30 | 1578.9 | 32.03 | 0.7690 | 161.1 | 643.9 | 482.8 |
| 110 | 43.3 | 247.00 | 232.30 | 1703.0 | 31.55 | 0.8280 | 167.1 | 644.8 | 477.7 |
| 115 | 46.1 | 266.10 | 251.40 | 1834.7 | 31.05 | 0.8910 | 173.1 | 645.7 | 472.6 |
| 120 | 48.9 | 286.40 | 271.70 | 1974.7 | 30.54 | 0.9590 | 179.1 | 646.4 | 467.3 |
| 125 | 51.7 | 307.80 | 293.10 | 2122.2 | 30.01 | 1.0310 | 185.2 | 647.1 | 461.9 |
| 130 | 54.4 | 330.70 | 316.00 | 2280.1 | 29.47 | 1.1080 | 191.4 | 647.6 | 456.2 |
Common Ammonia Properties
Operating an ammonia refrigeration facility?
NH3Edge provides OSHA PSM and EPA RMP compliance consulting for ammonia refrigeration facilities — third-party compliance audits, ammonia inventory determination, and continuous real-time inventory monitoring. Based in Salt Lake City, serving facilities nationwide.
Where the PT chart usually leads
A saturation pressure is normally the first input to a bigger question: how much ammonia is in the system, and does that put the facility under PSM and RMP?
Ammonia mass in a receiver, accumulator, or intercooler from its dimensions, liquid level, and pressure.
OpenFive questions to find out whether OSHA PSM and EPA RMP apply to your facility today.
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OpenWhat counts toward the PSM and RMP threshold quantity, and what facilities get wrong.
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