What Pressure Should R-404A Be?
Updated October 20, 2026
R-404A A1 Lower toxicity, no flame propagation
You are on a commercial refrigeration rack or a walk-in — a cooler or a freezer — with gauges connected and a suction number that only makes sense once you know the box temperature it is holding.
Judge freezer suction against cooler numbers and you will call a healthy box low, or miss a real starve; on refrigerated product, a wrong call spoils a load, not just a service call.
This page separates suction by application, walk-in cooler versus walk-in freezer, at the AHRI 1250 unit-cooler rating points, and gives discharge by outdoor temperature.
R-404A suction is about 14–18 psig at a −20°F walk-in freezer coil and 58–66 psig at a 25°F cooler coil, with discharge around 254–333 psig at 95°F outdoors. Suction follows the box through the evaporator coil temperature; discharge follows the outdoor air and the condenser[1]. Match your reading to the application and ambient in the tables below.
R-404A suction pressure: walk-in freezer vs cooler
Suction is set by the evaporator coil temperature, which is set by the box.
AHRI 1250-2020 rates walk-in unit coolers at a 25°F suction dew point for coolers, with 35°F air entering the coil, and −20°F for freezers, with −10°F air[2]. Those two points give the suction bands below.
| Application | Suction (psig / kPa) |
|---|---|
| Walk-in cooler (25°F coil) | 58–66 psig 400–458 kPa |
| Walk-in freezer (−20°F coil) | 14–18 psig 96–125 kPa |
Discharge (head) pressure by outdoor temperature
Discharge is set by the condenser: its condensing temperature is the outdoor air temperature plus the condenser's design TD[1], so head pressure climbs with the ambient. Sporlan's valve-selection chart for HTPG unit coolers assumes 110°F condensing for low temperature and 115°F for medium and high[3].
Find your outdoor temperature down the left column.
| Outdoor | Head (psig / kPa) |
|---|---|
| 65°F 18.3°C | 162–220 psig 1,117–1,518 kPa |
| 70°F 21.1°C | 175–237 psig 1,209–1,632 kPa |
| 75°F 23.9°C | 190–254 psig 1,307–1,753 kPa |
| 80°F 26.7°C | 204–273 psig 1,410–1,879 kPa |
| 85°F 29.4°C | 220–292 psig 1,518–2,012 kPa |
| 90°F 32.2°C | 237–312 psig 1,632–2,152 kPa |
| 95°F 35.0°C | 254–333 psig 1,753–2,298 kPa |
| 100°F 37.8°C | 273–356 psig 1,879–2,452 kPa |
| 105°F 40.6°C | 292–379 psig 2,012–2,614 kPa |
| 110°F 43.3°C | 312–404 psig 2,152–2,784 kPa |
| 115°F 46.1°C | 333–430 psig 2,298–2,962 kPa |
Reading a walk-in freezer: one worked example
Take a −20°F freezer coil at 95°F outdoors. Suction should read about 14–18 psig and discharge about 254–333 psig. To check superheat, look up the dew saturation temperature at your measured suction pressure and subtract it from the suction-line temperature; for subcooling, subtract the liquid-line temperature from the bubble saturation temperature at the liquid-line (high-side) pressure.
If suction is well below 14–18 psig with high superheat, suspect an undercharge or a restriction such as a plugged filter-drier[4][5]. Low suction with low or hunting superheat points instead to lost airflow, such as an iced or dirty coil[6][5].
Superheat checks
R-404A's glide is small (Sporlan: "just over 1°F"), but still read superheat on the dew curve and subcooling on the bubble curve[7]. There is no single blanket target.
Follow the equipment or valve manufacturer's figure for the box and metering device[8]. The superheat calculator and subcooling calculator do the saturation lookup for you from the measured pressure.
Readings that point to a problem
These are refrigeration faults; match a suspect reading to the pattern below, then confirm with a calculator before adding refrigerant.
A healthy R-404A system at 95°F outdoors reads about 58–66 psig suction on a 25°F cooler coil, 14–18 psig on a −20°F freezer coil, and 254–333 psig head.
| Fault | Suction | Head | Superheat | Subcooling | First thing to check |
|---|---|---|---|---|---|
| Likely undercharge | low | low | high | low | Find and fix the leak, then recharge by weight |
| Likely overcharge | high | high | low | high | Verify condenser airflow, then recover to target |
| Likely restriction | low | normal–low | high | high | Look for a temperature drop across the filter-drier or liquid line, then check the metering device. |
| Likely metering device overfeeding | high | low | low | low | A TXV or EEV stuck open or with a loose sensing bulb; on a fixed-orifice system, the piston size. |
Confirm a reading before adjusting the charge: the pressure diagnostic tool, low suction pressure and high head pressure guides walk a reading to its cause.
Frequently asked questions
What should R-404A suction pressure be on a walk-in freezer?
About 14–18 psig at the AHRI −20°F freezer coil temperature. It follows the box, not the weather: suction runs higher while a warm box pulls down (Heatcraft lists excessive load as a cause of high suction[5]) and settles into this band once the box is at temperature. A suction well below 14–18 psig once the box is cold points to a cause on Heatcraft's troubleshooting chart: a refrigerant shortage, a dirty or iced evaporator, or a clogged liquid-line filter-drier[5].
What should R-404A pressures be on a walk-in cooler?
Suction about 58–66 psig at the AHRI 25°F cooler coil temperature, with discharge around 254–333 psig at 95°F outdoors. Cooler suction runs well above freezer suction because the box is warmer; match your reading to the application, not to a single number.
What is normal R-404A discharge pressure?
About 254–333 psig at 95°F outdoors, rising on hotter days because the condensing temperature is the outdoor air plus the condenser's TD[1]. It follows the outdoor air and the condenser, not the box. Sporlan's valve-selection chart for HTPG unit coolers assumes 110°F condensing for low temperature and 115°F for medium[3]. Read the discharge chart above for your outdoor temperature.
What is R-404A running pressure at 95°F outdoors?
Discharge about 254–333 psig at 95°F outdoors; suction depends on the box: about 58–66 psig on a 25°F cooler coil and 14–18 psig on a −20°F freezer coil. Always pair the suction reading with the application temperature before judging it.
How these numbers are calculated
Every pressure here is R-404A's saturation pressure at the stated temperature, calculated with CoolProp 7.2.0.
Suction (low side) uses the saturated-vapor (dew) pressure; head (high side) uses the saturated-liquid (bubble) pressure[7].
Suction uses the AHRI 1250-2020 unit-cooler rating suction dew points, 25°F for a cooler and −20°F for a freezer[2], read on the dew curve with ±3°F shown as a band. Head uses a condensing temperature 10–30°F above the outdoor air: Heatcraft's condenser guide works with design TDs from 10 to 30°F[1], and AHRI 460 rates remote condensers at a 30°F TD, 95°F air and 125°F condensing[9].
We use 95°F as the reference because it is one of the AHRI 1250 outdoor rating temperatures for condensing units, with 59°F and 35°F[2].
Your equipment maker's charging chart or the unit data plate overrides these reference values for that specific system.
Sources
- [1]Heatcraft (Larkin) Air Cooled Condensers Technical Guide, LK-RACCTG. Heatcraft Refrigeration Products. September 2022. https://heatcraftrpd.com/dA/390c0f08b3/LK-TB-C-AIRCOOLED-1-26.pdf (accessed October 19, 2026)
- [2]AHRI Standard 1250 (I-P)-2020, Performance Rating of Walk-in Coolers and Freezers. AHRI. 2020. https://www.ahrinet.org/system/files/2023-06/AHRI-1250-%28I-P-2020%29_Performance_Rating_of_Walk-in_Coolers_and_Freezers.pdf (accessed October 19, 2026)
- [3]Sporlan Bulletin 500-10-RC, TEV Selection Chart for Heat Transfer Products Group Unit Coolers (October 2004). Sporlan (Parker). October 2004. https://media.htpg.com/site/htpg/_WP/img/docs/techdata/500-10-RC.PDF (accessed October 19, 2026)
- [4]Danfoss, Thermostatic Expansion Valve Troubleshooting, AC307572949567. Danfoss. 2017.12. https://assets.danfoss.com/documents/90976/AC307572949567en-010101.pdf (accessed October 19, 2026)
- [5]Heatcraft, Screw Compressor Condensing Units, Low Temperature Models: Installation and Operations Manual, H-IM-SCU-LT (October 2017), Table 11. Heatcraft Refrigeration Products. October 2017. https://www.heatcraftrpd.com/dA/e281e91712/H-IM-LTSCU.pdf (accessed October 19, 2026)
- [6]Sporlan Form 10-143, 12 Solutions for Fixing Common TEV Problems. Sporlan (Parker). 06/2012. https://www.parker.com/Literature/Sporlan/Sporlan%20pdf%20files/Sporlan%20pdf%20010/10-143.pdf (accessed October 19, 2026)
- [7]Sporlan Form 5-492, System Considerations for Refrigerant Blends with Temperature Glide. Sporlan (Parker). 2017. https://www.parker.com/content/dam/Parker-com/Literature/Sporlan/Sporlan-pdf-files/Sporlan-pdf-Educational/Form-5-492-Refrig-Blends.pdf (accessed October 19, 2026)
- [8]Sporlan Bulletin 10-9, Thermostatic Expansion Valves: Theory of Operation, Application, and Selection. Sporlan (Parker). March 2011. https://www.parker.com/content/dam/Parker-com/Literature/Sporlan/Sporlan-pdf-files/Sporlan-pdf-010/10-9.pdf (accessed October 19, 2026)
- [9]ANSI/AHRI Standard 460-2005, Performance Rating of Remote Mechanical-Draft Air-Cooled Refrigerant Condensers. AHRI. 2005. https://www.ahrinet.org/system/files/2023-06/ANSI_AHRI_Standard_460_2005.pdf (accessed October 19, 2026)