What Pressure Should R-454B Be?
Updated October 26, 2026
R-454B A2L Lower toxicity, lower flammability
EPA lists R-454B for new residential air conditioners and heat pumps.[21] Of the Carrier, Trane, Rheem, York and Lennox R-454B documents we checked, only Lennox's EL18KSLV instructions give a pressure table by outdoor temperature. Lennox does, for its EL18KSLV heat pump, and that is the source for this page.
The numbers below are charge-mode pressures, read with the unit forced to full capacity for a charge check, not the pressures a system shows in ordinary operation. Treat them as a charging reference, and confirm against the unit's own label.
Lennox's EL18KSLV heat pump instructions list R-454B pressures by outdoor temperature, measured in the unit's charge mode. At 95°F outdoors they show 138–142 psig vapor (low side) and 322–351 psig liquid (high side) for the ‑024 and ‑036 sizes. Lennox labels these charge-mode values, not normal operating pressures.[1]
R-454B pressures by outdoor temperature (charge mode)
| Outdoor | -024 low side | -024 high side | -036 low side | -036 high side |
|---|---|---|---|---|
| 65°F 18°C | 137 psig 945 kPa | 202 psig 1,393 kPa | 133 psig 917 kPa | 224 psig 1,544 kPa |
| 70°F 21°C | 137 psig 945 kPa | 221 psig 1,524 kPa | 133 psig 917 kPa | 244 psig 1,682 kPa |
| 75°F 24°C | 138 psig 951 kPa | 240 psig 1,655 kPa | 134 psig 924 kPa | 265 psig 1,827 kPa |
| 80°F 27°C | 139 psig 958 kPa | 261 psig 1,800 kPa | 135 psig 931 kPa | 286 psig 1,972 kPa |
| 85°F 29°C | 138 psig 951 kPa | 275 psig 1,896 kPa | 134 psig 924 kPa | 306 psig 2,110 kPa |
| 90°F 32°C | 140 psig 965 kPa | 298 psig 2,055 kPa | 136 psig 938 kPa | 324 psig 2,234 kPa |
| 95°F 35°C | 142 psig 979 kPa | 322 psig 2,220 kPa | 138 psig 951 kPa | 351 psig 2,420 kPa |
| 100°F 38°C | 144 psig 993 kPa | 349 psig 2,406 kPa | 140 psig 965 kPa | 375 psig 2,586 kPa |
| 105°F 41°C | 145 psig 1,000 kPa | 374 psig 2,579 kPa | 141 psig 972 kPa | 402 psig 2,772 kPa |
| 110°F 43°C | 146 psig 1,007 kPa | 394 psig 2,717 kPa | 142 psig 979 kPa | 420 psig 2,896 kPa |
| 115°F 46°C | 147 psig 1,014 kPa | 420 psig 2,896 kPa | 143 psig 986 kPa | 449 psig 3,096 kPa |
Lennox EL18KSLV installation instructions 508700-01 (12/2024), Table 6, within ±10 psig liquid and ±5 psig vapor, at an indoor airflow of 800 SCFM (‑024) and 1,050 SCFM (‑036). The ‑048/‑060 column is left out: as printed, its pressures fall as the outdoor temperature rises.[1]
What charge mode is
A DIP switch on the display board puts the unit in charge mode. Lennox has start-up and testing done at 100% capacity; after 10 minutes, the subcooling shown on the display is compared with the target for the indoor unit in its Table 4, and refrigerant is added if it reads low or recovered if it reads high.[1]
What the pressures mean in temperature
At 95°F outdoors, the 138–142 psig vapor range is a 53.6–55.2°F dew point and the 322–351 psig liquid range a 104.8–111.1°F bubble point, 10–16°F above the outdoor air.[16] See the R-454B PT chart.
R-454B vs R-410A and R-32
At 95°F outdoors:
| Refrigerant and basis | Low side | High side |
|---|---|---|
| R-454B, Lennox EL18KSLV, charge mode, 2 sizes | 138–142 psig | 322–351 psig[1] |
| R-410A, Lennox tables, 37 units | 134–151 psig | 336–404 psig[2][3][4][5][6][7] |
| R-410A, Goodman (80°F/67°F) and Lennox, 63 units | 134–155 psig | 329–413 psig[8][9][10][2][3][4][5][6][7] |
| R-32, Goodman and Amana (80°F/67°F), 26 units | 131–153 psig | 348–453 psig[11][12][13][14][15] |
At equal saturation temperatures R-454B runs below both: at a 45°F dew point, R-454B is 118 psig against 130 psig for R-410A and 133 psig for R-32; at a 110°F bubble point, 346, 366 and 375 psig.[16]
Standing pressure (system off)
With the system off long enough for pressures to equalize, the gauges read the saturation pressure of the liquid refrigerant at its temperature; for a blend held as liquid in a closed container, Arkema gives the liquid (bubble) pressure as the one that applies.[17] During the off cycle, refrigerant migrates toward the coldest part of the system, so the reading follows that spot's temperature rather than the outdoor air.[18] NIST notes that non-condensable gas can be diagnosed from its partial pressure while the system is off.[19]
| Off temperature | Standing (psig / kPa) |
|---|---|
| 65°F 18.3°C | 175 psig 1,209 kPa |
| 70°F 21.1°C | 191 psig 1,313 kPa |
| 75°F 23.9°C | 206 psig 1,424 kPa |
| 80°F 26.7°C | 223 psig 1,540 kPa |
| 85°F 29.4°C | 241 psig 1,663 kPa |
| 90°F 32.2°C | 260 psig 1,793 kPa |
| 95°F 35.0°C | 280 psig 1,930 kPa |
| 100°F 37.8°C | 301 psig 2,074 kPa |
| 105°F 40.6°C | 323 psig 2,225 kPa |
| 110°F 43.3°C | 346 psig 2,385 kPa |
| 115°F 46.1°C | 370 psig 2,552 kPa |
Readings that point to a problem
Faults show up as a pattern across suction, head pressure, superheat and subcooling, compared with the same system running normally.[19] NIST measured these patterns on a 2.5-ton R-410A heat pump with a TXV in cooling mode, and its report also reproduces Breuker and Braun's chart for a rooftop unit with a fixed orifice.[19]
| Fault | Suction | Head | Superheat | Subcooling |
|---|---|---|---|---|
| Undercharge, superheat still under 16°F | no change detected | lower | no change detected | lower |
| Undercharge, superheat above 16°F | lower | lower | higher | lower |
| Overcharge | no change detected | higher | no change detected | higher |
| Liquid-line restriction, superheat above 16°F | lower | lower | higher | higher |
| Low indoor airflow | lower | lower | no change detected | no change detected |
| Low outdoor airflow, superheat under 16°F | higher | higher | no change detected | lower |
| Low outdoor airflow, superheat above 16°F | lower | higher | higher | lower |
| Compressor valve leakage | higher | lower | no change detected | lower |
NIST split its results at 9°C (16.2°F) of superheat, where the TXV runs out of control range. A liquid-line restriction caused no detectable change below that point. Overcharge, low indoor airflow and compressor leakage never pushed superheat past it at the fault levels tested.[19]
| Fault | Suction | Head | Superheat | Subcooling |
|---|---|---|---|---|
| Refrigerant leak (undercharge) | lower | lower | higher | lower |
| Liquid-line restriction | lower | lower | higher | higher |
| Condenser fault (blocked coil) | higher | higher | lower | lower |
| Evaporator fault | lower | lower | lower | lower |
| Compressor valve leakage | higher | lower | lower | lower |
Neither NIST chart covers an overcharged fixed-orifice system. DOE's flowchart below does.
DOE's order of checks
DOE's Building America diagnostics guide works through the readings in order once the indoor coil's temperature split runs more than 3°F below its target, with separate charts for fixed-orifice and TXV systems.[20]
| Reading | Fixed orifice | TXV |
|---|---|---|
| Condensing temperature too far above outdoor air | Non-condensables, fouled condenser coil, overcharge or liquid-line restriction | Same |
| Evaporator saturation temperature too low | Liquid-line restriction, fouled evaporator coil or low charge | Same, or the TXV is out of adjustment |
| Low subcooling, low superheat | Expansion device overfeed or fouled evaporator coil | TXV overfeed: unsecured bulb or adjustment |
| Low subcooling, high superheat | Undercharge | Undercharge, or TXV underfeed: bad power element or adjustment |
| High subcooling, low superheat | Overcharge | Overcharge, or TXV overfeed |
| High subcooling, high superheat | Low outdoor temperature | Undercharge, or TXV underfeed |
DOE gives its limits as starting points. Its Table 3 lists a maximum condensing-over-ambient of 25°F above 12 SEER, 30°F at 10–12 SEER and 35°F below 10 SEER, and a minimum evaporator saturation temperature of 35°F, 40°F and 45°F alongside indoor wet bulbs of 62–63°F, 64–65°F and 66–67°F.[20] It adds that non-condensables or a liquid-line restriction also raise subcooling.[20]
Frequently asked questions
What's the normal operating pressure of R-454B at 95°F outdoor?
Lennox's EL18KSLV charge-mode table lists 138–142 psig vapor and 322–351 psig liquid at 95°F; Lennox labels these charge-mode values, not normal operating pressures.[1]
How does R-454B compare to R-410A?
How does R-454B compare to R-32?
At equal saturation temperatures R-454B sits below R-32: 118 vs 133 psig at a 45°F dew point and 346 vs 375 psig at a 110°F bubble point.[16]
Can I use R-410A recovery equipment for R-454B?
Lennox's EL18KSLV instructions call for recovery equipment suitable for flammable refrigerants where applicable, with its electrical components sealed against ignition, and say not to mix refrigerants in recovery units or cylinders.[1]
How is the charge checked on an R-454B heat pump?
In charge mode, Lennox runs the unit at 100% capacity, then after 10 minutes compares the subcooling on the display with the target in its Table 4, adding refrigerant if it reads low or recovering if it reads high.[1]
How these numbers are calculated
The pressure table on this page is Lennox's charge-mode Table 6 for the EL18KSLV, extracted from the PDF by script and checked against the page image.[1]
The ‑048/‑060 column is left out because its printed liquid and vapor pressures fall as the outdoor temperature rises, which the other two sizes and basic physics do not.[1]
Saturation-temperature conversions and the standing-pressure table come from the site's R-454B pressure–temperature data (CoolProp 7.2.0).[16]
Sources
- [1]Elite Series EL18KSLV Units installation instructions 508700-01. Lennox. 12/2024. https://www.lennox.com/dA/9ab528c680/508700-01.pdf (accessed October 20, 2026). Table 6. Charge Mode Operating Pressures, PDF p. 26 — R-454B charge-mode liquid and vapor pressures by outdoor temperature.
- [2]Elite Series XC13 Units installation instructions 506635-01. Lennox. 09/11. https://www.lennox.com/dA/1ac2b167d5/Lennox_XC13_IOM.pdf (accessed October 20, 2026). Table 4. Normal Operating Pressures, PDF p. 26 — R-410A typical liquid and suction/vapor operating pressures by outdoor temperature.
- [3]Merit Series 14ACX Units installation instructions 506645-01. Lennox. 07/11. https://www.lennox.com/dA/8b22f61eb8/Lennox_14ACX_IOM.pdf (accessed October 20, 2026). Table 4. HFC-410A Normal Operating Pressures, PDF p. 27 — R-410A typical liquid and suction/vapor operating pressures by outdoor temperature.
- [4]XC21 Series Units service literature Corp. 0504-L2. Lennox. 07/2009. https://tech.lennoxintl.com/C03e7o14l/VIu12Ch2uV/0504g.pdf (accessed October 20, 2026). Table 10. Normal Operating Pressures, PDF p. 18 — R-410A typical liquid and suction/vapor operating pressures by outdoor temperature.
- [5]Elite Series XP16 Units installation instructions 506640-01. Lennox. 12/10. https://www.lennox.com/lib/legacy-res/pdfs/installation_maintenance/lennox_xp16_iom.pdf (accessed October 20, 2026). Table 7. Normal Operating Pressures, PDF p. 29 — R-410A typical liquid and suction/vapor operating pressures by outdoor temperature.
- [6]XP17 System installation instructions 506586-01. Lennox. 06/11. https://www.lennox.com/lib/legacy-res/pdfs/installation_maintenance/lennox_xp17_iom.pdf (accessed October 20, 2026). Table 10. Normal Operating Pressure, PDF p. 31 — R-410A typical liquid and suction/vapor operating pressures by outdoor temperature.
- [7]Merit Series 13HPX Units installation instructions 506727-01. Lennox. 06/11. https://www.lennox.com/dA/138cce8866/Lennox_13HPX_IOM.pdf (accessed October 20, 2026). Table 4. Normal Operating Pressures, PDF p. 27-28 — R-410A typical liquid and suction/vapor operating pressures by outdoor temperature.
- [8]GSX14 Split System Air Conditioner, up to 15 SEER (spec sheet SS-GSX14). Goodman. 1/19. https://apps.goodmanmfg.com/brochures/files/5c5085ab40be5SS-GSX14.pdf (accessed October 20, 2026). Expanded Cooling Data — R-410A liquid (Hi PR) and suction (Lo PR) pressures at the service valves, by outdoor temperature and indoor condition.
- [9]GSX16 Split System Air Conditioner (spec sheet SS-GSX16). Goodman. 3/21. https://apps.goodmanmfg.com/brochures/files/6062166241d6dSS-GSX16.pdf (accessed October 20, 2026). Expanded Cooling Data — R-410A liquid (Hi PR) and suction (Lo PR) pressures at the service valves, by outdoor temperature and indoor condition.
- [10]DSXC18 Split System Air Conditioner, up to 18 SEER (spec sheet SS-DSXC18). Goodman. 11/16. https://apps.goodmanmfg.com/brochures/files/582b1bf6dd15bSS-DSXC18.pdf (accessed October 20, 2026). Expanded Cooling Data — R-410A liquid (Hi PR) and suction (Lo PR) pressures at the service valves, by outdoor temperature and indoor condition.
- [11]GXV6S Variable-Speed R-32 Split System Air Conditioner, up to 17.2 SEER2 (spec sheet SS-GXV6S-R32). Goodman. 07/25. https://apps.goodmanmfg.com/brochures/files/68ed3c631108aSS-GXV6S-R32.pdf (accessed October 20, 2026). Expanded Cooling Data — R-32 liquid (Hi PR) and suction (Lo PR) pressures at the service valves, by outdoor temperature and indoor condition.
- [12]GXV9S Variable-Speed R-32 Split System Air Conditioner, up to 19 SEER2 (spec sheet SS-GXV9S-R32). Goodman. 07/25. https://apps.goodmanmfg.com/brochures/files/68ed3d136d70fSS-GXV9S-R32.pdf (accessed October 20, 2026). Expanded Cooling Data — R-32 liquid (Hi PR) and suction (Lo PR) pressures at the service valves, by outdoor temperature and indoor condition.
- [13]AXV9S Variable-Speed R-32 Split System Air Conditioner, up to 19 SEER2 (spec sheet SS-AXV9S-R32). Amana. 07/25. https://apps.goodmanmfg.com/brochures/files/68ee8aca01ff7SS-AXV9S-R32.pdf (accessed October 20, 2026). Expanded Cooling Data — R-32 liquid (Hi PR) and suction (Lo PR) pressures at the service valves, by outdoor temperature and indoor condition.
- [14]AZV9S Variable-Speed R-32 Split System Heat Pump, up to 21.0 SEER2 (spec sheet SS-AZV9S-R32). Amana. 09/25. https://apps.goodmanmfg.com/brochures/files/68ee8c439a303SS-AZV9S-R32.pdf (accessed October 20, 2026). Expanded Cooling Data — R-32 liquid (Hi PR) and suction (Lo PR) pressures at the service valves, by outdoor temperature and indoor condition.
- [15]AZV7S Variable-Speed R-32 Split System Heat Pump, up to 19.0 SEER2 (spec sheet SS-AZV7S-R32). Amana. 07/25. https://apps.goodmanmfg.com/brochures/files/68ee8e7c8878dSS-AZV7S-R32.pdf (accessed October 20, 2026). Expanded Cooling Data — R-32 liquid (Hi PR) and suction (Lo PR) pressures at the service valves, by outdoor temperature and indoor condition.
- [16]CoolProp 7.2.0. CoolProp (I. H. Bell, J. Wronski, S. Quoilin, V. Lemort). https://coolprop.org/ (accessed October 2, 2026). Bell, I. H.; Wronski, J.; Quoilin, S.; Lemort, V. Pure and Pseudo-pure Fluid Thermophysical Property Evaluation and the Open-Source Thermophysical Property Library CoolProp. Ind. Eng. Chem. Res. 53, 2498–2508 (2014). https://doi.org/10.1021/ie4033999
- [17]Liquid or Vapor Pressure: Which One Do You Need for Your Application? Arkema (Forane). https://forane.arkema.com/en/resources/tech-tips/liquid-or-vapor-pressure/ (accessed October 20, 2026). which saturation pressure (liquid/bubble vs vapor/dew) applies to a blend held as liquid in a closed container.
- [18]Scroll compressors SH090 to SH485, R410A: Application guidelines, AB243586442172en-US1301. Danfoss. https://assets.danfoss.com/documents/90219/AB243586442172en-US1301.pdf (accessed October 20, 2026). p. 31, off-cycle migration — refrigerant migrates to the coldest part of the system during the off cycle.
- [19]NIST Special Publication 1087, Cooling Mode Fault Detection and Diagnosis Method for a Residential Heat Pump (M. Kim, S. H. Yoon, W. V. Payne, P. A. Domanski). National Institute of Standards and Technology. October 2008. https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication1087.pdf (accessed October 20, 2026). Table 5.1(a) p. 40 and Table 5.2 p. 41, fault-direction charts; Section 5.4.1 p. 58 — residential heat-pump cooling-mode fault patterns.
- [20]Measure Guideline: Air Conditioner Diagnostics, Maintenance, and Replacement (D. Springer, B. Dakin), NREL/SR-5500-56283. U.S. DOE Building America. March 2013. https://www1.eere.energy.gov/buildings/publications/pdfs/building_america/measure_guide_air_cond_diagnostics.pdf (accessed October 20, 2026). Section 3.4 pp. 32–33, Table 3 p. 32, Figures 17–18 p. 33 — order-of-checks diagnostic flowcharts for fixed-orifice and TXV systems.
- [21]U.S. EPA, Fact Sheet — Final Rule 23: Protection of Stratospheric Ozone: New Listings for the Significant New Alternatives Policy Program. U.S. EPA. April 23, 2021. https://www.epa.gov/sites/default/files/2021-04/documents/fact_sheet_snap_final_rule_23_final_4-23-21_508.pdf (accessed October 25, 2026). Listing table, end use 'Residential and light commercial air conditioning and heat pumps (New)' — SNAP lists these A2Ls for new equipment only (R-32: same, excluding self-contained room air conditioners).