What Pressure Should R-407C Be?
Updated October 1, 2026
R-407C A1 Lower toxicity, no flame propagation
You are on an R-407C system — an R-22 replacement found in retrofits and light-commercial AC — with gauges connected and two saturation temperatures printed on the dial. The glide is what makes R-407C confusing to read.
Read superheat off the wrong curve and you can be off by the whole glide, which is enough to condemn a good charge or clear a bad one. That mistake sends good refrigerant to a recovery tank or leaves a starving evaporator.
This page gives the suction and discharge to expect at each outdoor temperature in psig, bar and kPa, explains which curve to read for which job, and gives the standing range.
R-407C runs about 60–71 psig (4.2–4.9 bar) suction and 260–299 psig discharge at 95°F outdoors, with a 38–45°F indoor coil. At the same conditions that is about 7–8% lower on suction and about 15% higher on discharge than R-22. Because it glides, read suction on the dew curve and the liquid line on the bubble curve.
R-407C suction and discharge pressure chart
Find the outdoor temperature down the left column. Suction is read on the dew curve; discharge tracks the weather. Bar values are in the next section.
| Outdoor | Low side (psig / kPa) | High side (psig / kPa) |
|---|---|---|
| 65°F 18.3°C | 60–71 psig 416–488 kPa | 166–194 psig 1,143–1,338 kPa |
| 70°F 21.1°C | 60–71 psig 416–488 kPa | 180–209 psig 1,238–1,444 kPa |
| 75°F 23.9°C | 60–71 psig 416–488 kPa | 194–225 psig 1,338–1,555 kPa |
| 80°F 26.7°C | 60–71 psig 416–488 kPa | 209–242 psig 1,444–1,672 kPa |
| 85°F 29.4°C | 60–71 psig 416–488 kPa | 225–260 psig 1,555–1,794 kPa |
| 90°F 32.2°C | 60–71 psig 416–488 kPa | 242–279 psig 1,672–1,923 kPa |
| 95°F 35.0°C | 60–71 psig 416–488 kPa | 260–299 psig 1,794–2,059 kPa |
| 100°F 37.8°C | 60–71 psig 416–488 kPa | 279–319 psig 1,923–2,201 kPa |
| 105°F 40.6°C | 60–71 psig 416–488 kPa | 299–341 psig 2,059–2,349 kPa |
| 110°F 43.3°C | 60–71 psig 416–488 kPa | 319–363 psig 2,201–2,505 kPa |
| 115°F 46.1°C | 60–71 psig 416–488 kPa | 341–387 psig 2,349–2,668 kPa |
The chart holds the low side at one band because it depends mainly on the 38–45°F indoor coil; real readings move a little with the weather, far less than the high side.
Why R-407C needs two temperatures: glide (dew for suction, bubble for the liquid line)
R-407C is a zeotropic blend, so a single pressure has two saturation temperatures — a lower dew point (saturated vapor) and a higher bubble point (saturated liquid). The gap between them is the glide, several degrees across the working range. Use the dew curve for suction and(/superheat-calculator/); use the bubble curve for the liquid line and(/subcooling-calculator/). Reading the wrong curve is the classic R-407C service error.
Running pressure in bar and kPa
At 95°F outdoors the low side is about 60–71 psig, which is 4.2–4.9 bar (gauge) or 416–488 kPa (gauge); the high side is about 260–299 psig, which is 17.9–20.6 bar (gauge) or 1,794–2,059 kPa (gauge). The chart above lists psig with kPa for every 5°F step; multiply psig by 0.0689 for bar.
Standing pressure is a range, not one number
Once the system has been off long enough for the pressures to equalize, R-407C does not read one pressure — it reads across a dew-to-bubble range at the temperature of the coolest part of the system (indoor or outdoor). The spread is the glide, so treat standing pressure as a band, not a single target.
| Off temperature | Standing (dew–bubble, psig / kPa) |
|---|---|
| 65°F 18.3°C | 107–129 psig 736–889 kPa |
| 70°F 21.1°C | 117–141 psig 809–969 kPa |
| 75°F 23.9°C | 129–153 psig 886–1,054 kPa |
| 80°F 26.7°C | 141–166 psig 969–1,143 kPa |
| 85°F 29.4°C | 153–180 psig 1,056–1,238 kPa |
| 90°F 32.2°C | 167–194 psig 1,149–1,338 kPa |
| 95°F 35.0°C | 181–209 psig 1,248–1,444 kPa |
| 100°F 37.8°C | 196–225 psig 1,352–1,555 kPa |
| 105°F 40.6°C | 212–242 psig 1,463–1,672 kPa |
| 110°F 43.3°C | 229–260 psig 1,579–1,794 kPa |
| 115°F 46.1°C | 247–279 psig 1,702–1,923 kPa |
If the low side reads 28 psig
At 28 psig on the low side, R-407C's dew (saturated-vapor) temperature is about 10°F and its bubble (saturated-liquid) temperature about −2°F. Subtract the dew temperature from your suction-line temperature for superheat; do not use the bubble temperature there or you will read the glide as extra superheat.
Off readings on an R-407C system
Match a suspect reading to the pattern below — reading superheat and subcooling on the dew and bubble curves respectively — then confirm with a calculator before you add or remove refrigerant.
A healthy R-407C system at 95°F outdoors reads about 60–71 psig on the low side and 260–299 psig on the high side.
| 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 are normal R-407C suction and discharge pressures?
About 60–71 psig suction and 260–299 psig discharge at 95°F outdoors with a 38–45°F indoor coil. Suction depends mainly on the indoor coil and moves far less than discharge, which climbs with the outdoor temperature. Read the chart above for your ambient, and read suction on the dew curve.
What is R-407C running pressure in bar?
About 4.2–4.9 bar (gauge) on the low side and 17.9–20.6 bar (gauge) on the high side at 95°F outdoors — the same as 60–71 psig and 260–299 psig. To convert any reading, multiply psig by 0.0689 to get bar (gauge).
If the R-407C low side reads 28 psig, what is the evaporating temperature?
At 28 psig the dew (saturated-vapor) temperature is about 10°F and the bubble (saturated-liquid) temperature about −2°F. Use the dew value — about 10°F — as the evaporating temperature for superheat; the gap between the two is R-407C's glide.
Why do R-407C gauges show two temperatures?
Because R-407C is a zeotropic blend that evaporates and condenses across a temperature range, not at one point. Every pressure has a lower dew temperature and a higher bubble temperature. Read the dew scale for suction and superheat, and the bubble scale for the liquid line and subcooling.
How these numbers are calculated
Every pressure here is R-407C'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.
For the low side we read a 38–45°F indoor evaporator coil: the low side depends mainly on the indoor coil (indoor temperature and airflow) and moves far less than the high side, which we take as a condenser running 15–25°F above the outdoor air. We use 95°F as the reference because it is the outdoor temperature in the AHRI 210/240 A2 rating test (95°F outdoors, 80°F/67°F indoors).
Sources: CoolProp 7.2.0; AHRI 210/240-2023 (rating conditions). Your equipment maker's charging chart or the unit data plate overrides these reference values for that specific system.