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How to Use the Refrigerant Blend Calculator
Choose a preset such as R-407C, R-448A or R-454B, or add components and enter the mass percent of each. The percents must total 100.
Enter the evaporating and condensing pressures in bar(a), kPa(a) or PSIG. Leave a field blank to skip that side.
Press Calculate. The tool returns the blended GWP, the safety class, and the bubble point, dew point and glide at each pressure.
Use the dew point for superheat and the bubble point for subcooling. Charge zeotropic blends as liquid.
How refrigerant blends behave
Most refrigerants in current HVAC and refrigeration equipment are blends, not pure compounds. R-410A is a 50/50 mass blend of R-32 and R-125. R-407C mixes R-32, R-125 and R-134a at 23, 25 and 52 percent. R-449A has four components and R-448A has five. A blend does not boil at one temperature the way a pure fluid does, and that changes how you read pressures, set superheat and charge a system.
Azeotropic and zeotropic blends
An azeotrope boils and condenses at one temperature for a given pressure, and its composition does not change as it does. R-507A is one, with no glide in the calculator. R-410A has a glide of only 0.1 K at 5 bar(a) and R-404A 0.5 K, so they behave almost like pure fluids. A zeotropic blend such as R-407C glides 6.4 K at the same pressure, because the more volatile components boil first. That is why zeotropic blends must be charged as liquid. Pulling vapour from the cylinder removes the volatile components faster than the heavy ones and leaves the wrong blend in the system and in the cylinder. Confirm the total charge with the refrigerant charge calculator before you start.
Dew point for superheat, bubble point for subcooling
Superheat is the suction temperature minus the saturation temperature at suction pressure, and for a blend that saturation temperature has two values. The vapour is only fully evaporated at the dew point, so superheat is measured from the dew point. Subcooling is measured from the bubble point, because that is where the liquid starts to boil. If you use the bubble point for superheat, you overstate the result by the glide, which is 6.4 K for R-407C at 5 bar(a). The superheat calculator takes the saturation temperature you read from this tool.
Entering pressure in the right unit
Saturation depends on absolute pressure, but service gauges read gauge pressure. The tool accepts bar(a), kPa(a) or PSIG and adds 14.696 psi of atmospheric pressure to a gauge reading, so readings taken at altitude carry a small offset. When your gauges and the equipment data sheet use different units, convert with the pressure converter and enter either one. The pressure fields keep your value when you switch units.
How a blend GWP is calculated
The GWP of a blend is the sum of each component's mass fraction times its own GWP. R-407C works out to 1,774, R-404A to 3,922 and R-454B to 466. The GWP is a property of the blend, not of the equipment, so it does not change with pressure. Whether a blend is still allowed for a new application depends on the rules for that application, and the refrigerant regulation checker is the place to look it up.
Canadian HFC rules and what they count
Environment and Climate Change Canada regulates HFCs through the Ozone-depleting Substances and Halocarbon Alternatives Regulations, which limit the HFCs that can enter Canada and the import and manufacture of certain products that use them. The department describes the program on its regulations information page. Because the program weighs HFCs by climate impact, the blend GWP above is the number that matters when you compare a retrofit refrigerant with the one it replaces. The refrigerant phaseout guide covers the timeline.
Safety class of a blend
ASHRAE 34 gives each blend a class from flammability and toxicity testing of the formulation, including the worst case of fractionation. The class is not an average of the components. R-410A contains A2L R-32 and is classed A1, while R-454B and R-454C are A2L. For the 12 presets the tool shows the published class. For a custom blend it shows the share of A2L and A3 components by mass and leaves the class blank, because only testing can assign one.
How the temperatures are calculated
The tool solves the bubble and dew point of the mixture with the Peng-Robinson equation of state, with interaction parameters fitted to CoolProp. Against CoolProp, the 12 preset blends agree to within 0.4 K on bubble point, dew point and glide from 2 to 18 bar(a). Reference-grade values for any blend come from NIST REFPROP. For commissioning, use the manufacturer pressure-temperature chart for the exact blend and treat the figures here as a fast check.
Frequently Asked Questions
Glide is the difference between the dew point and the bubble point of a blend at one pressure. At 5 bar(a), R-407C boils from -3.9°C to 2.5°C, a glide of 6.4 K, while R-410A glides only 0.1 K and R-507A has none. The saturation temperature of a high-glide blend changes along the coil, so the reference point you pick for superheat and subcooling changes the answer by up to the full glide.
It is the mass-weighted average of the GWP of each component. R-407C is 23% R-32 (675), 25% R-125 (3,500) and 52% R-134a (1,430), so 0.23 x 675 + 0.25 x 3,500 + 0.52 x 1,430 gives 1,774. The tool uses 100-year GWP values from the IPCC Fourth Assessment Report, with R-1234yf at 4 and R-1234ze(E) at 7, which are the values behind the published blend GWPs.
The components of a zeotropic blend have different vapour pressures. Vapour drawn from the cylinder is richer in the more volatile components, such as R-32 in R-407C, so the composition entering the system is wrong and the liquid left in the cylinder drifts the other way. Charge zeotropic blends as liquid, meter it into the system, and follow the cylinder label.
Use the dew point for superheat and the bubble point for subcooling. For R-407C at 5 bar(a) the dew point is 2.5°C and the bubble point is -3.9°C. Taking superheat from the bubble point would overstate it by 6.4 K. At a condensing pressure of 18 bar(a) the glide is 4.9 K, so taking subcooling from the dew point would understate it by that amount.
ASHRAE 34 assigns a safety class to a blend from flammability and toxicity testing of the formulation, including its worst case of fractionation. The class cannot be averaged from the components. R-410A contains A2L R-32 and is still A1, while R-454B is A2L. Presets show the published class, and a custom blend shows the share of A2L and A3 components by mass.