Refrigerant Blends
- SkillCat Team
- Sep 16
- 6 min read
EPA 608 Core Chapter 6
Purpose of Refrigerant Blends
In this module, we will introduce refrigerant blends and discuss how to use them in HVAC practices.
Overview of Refrigerant Blends
As we discussed in the previous module, refrigerants used in the past were found to be harmful to humans and the environment. These refrigerants were phased out in the US and internationally.
After they were phased out, CFC and HCFC refrigerants could no longer be used. So what happens to equipment that operated on those refrigerants? This is why refrigerant blends were created.
During the time before CFCs and HCFCs had to be fully phased out, the industry developed refrigerant blends. Refrigerant blends were developed to match properties of the refrigerants originally used.
Refrigerant blends contain a mixture of two or more refrigerants. Generally, a refrigerant blend will contain two refrigerants.
If it contains three refrigerants, the term for that is a ternary blend.
For example, R-407c is a ternary blend of three HFC refrigerants. It contains:
23% R-32
25% R-125, and
52% R-134
Refrigerant blends are standardized by manufacturers and have their own ASHRAE numbers. R-407c, like we just discussed, is a unique ASHRAE number.
Can Technicians Create Their Own Blends?
Refrigerant blends are manufactured by companies like Honeywell or DuPont. Blends are made to have specific properties in specific ratios. Otherwise they won’t work in an HVAC system.
Technicians cannot mix their own refrigerants. Mixing your own refrigerant is illegal and the technician is subject to fines.
If technicians mix refrigerants, the resulting refrigerant is basically a mixture with unknown quantities. The mixture can no longer be used.
This is because this mix will have different properties than what the equipment was originally designed for.
Mixing your own refrigerants would be the same as mixing your own gasoline to put into your car. You wouldn’t do that because your car is a complex machine that needs a specific blend of chemicals to run. HVAC systems are the same way.
If the technician mixes their own refrigerants, this
Creates unpredictable temperature changes, and
Places stress on equipment
All of this can cause equipment to fail and not work properly.
Putting this mix into an HVAC system will also void the warranty of the equipment. This because it goes against the manufacturer’s guidelines for use.
These reasons are why technicians should never mix their own refrigerants.
If technicians accidentally mix their own refrigerants and sent the mixture to be reclaimed, the reclaimer may:
Refuse to accept it, or
Destroy the refrigerant at the owner’s expense.
It is very expensive to destroy refrigerant.
In this module, we discussed how were the refrigerant blends developed and the properties of different refrigerant blends.
Types of Refrigerant Blends
In this module, we will dive deeper into the different types of refrigerant blends and discuss how they are used in HVAC practices.
Overview
Depending on what refrigerants were blended together, refrigerant blends can have different properties. Let’s take a look at a video that gives you a brief overview of this.
As mentioned in the video, there are two different types of refrigerant blends:
- Zeotropic Blends
- Azeotropic Blends
Zeotropic Blends
Zeotropic blends are mixtures of two or more refrigerants that have different boiling points. Recall that a boiling point is when something changes from liquid to gas.
This means that in a zeotropic blend, the components will boil and condense at different temperatures. The different refrigerants in the blend will act separately of each other.
Think of a pot of boiling water with oil. While the water is boiling, the oil is still in liquid form. This is what happens in a zeotropic blend.
R-407c is an example of a zeotropic blend that we commonly see. In general, all refrigerants with an ASHRAE number of 400 are zeotropic.
R-407c is a blend of all HFC refrigerants including:
- R-32
- R-125
- R-134a
Azeotropic Blends
Azeotropic blends are a mixture of two or more refrigerants that have the same boiling point. They will boil and condense at the same temperature.
In an azeotropic blend, the refrigerants will act like a single refrigerant.
R-502 is an example of an azeotropic blend that we commonly see.
R-502 is a blend of
- R-22 (HCFC)
- R-115 (CFC)
In this module, we discussed how were the different types of refrigerant blends developed.
Properties of Refrigerant Blends
In this module, we will discuss various properties of refrigerant blends.
Temperature Glide
With zeotropic blends, we have to consider temperature glide. Temperature glide is the difference between the dew point and the bubble point.
The dew point is the temperature at which the first refrigerant in a blend turns from vapor to liquid. The dew point is specific to refrigerant blends. This is the same as the temperature of condensation in single refrigerants.
For example, in R-407c, the first refrigerant condenses at 21.94°F. So the dew point of R-407c is 21.94°F.
And the bubble point is the temperature at which the first refrigerant in a blend starts to turn from liquid to vapor. Like the dew point, the bubble point is specific to refrigerant blends. It’s the same as a boiling point in single refrigerants.
For example, in the blend R-407c, the first refrigerant starts to boil at 10.44°F. So the bubble point of R-407c is 10.44°F.
As we said, temperature glide is the difference between these two points.
Since the dew point is 21.94°F and the bubble point is 10.44°F, the temperature glide is the difference. 21.94°F - 10.44°F = 11.5°F So the temperature glide of R-407c would be 11.5°F.
Fractionation
Recall that charging is when you add refrigerant into a system. It’s less like charging your phone and more like filling up your gas tank.
Blended refrigerants need to be charged as a liquid. This is because there are different refrigerants in the blend that may be spread out unevenly.
We call this separation fractionation. It occurs when the refrigerant is a vapor. Fractionation is when the different refrigerants in a blend settle into layers.
Think of a glass containing oil, water, and sand. If you leave the mixture, it will settle into three layers. If you then pour out some of the mixture, it will be mostly the oil that is poured out.
The same thing is happening with this blended refrigerant in vapor form. If you charge this separated refrigerant blend, you will not get the full blend. You will get what is on top of the mixture. That is why we charge blends as a liquid.
Fractionation is a problem particularly with the refrigerant blend R-407c. This is because R-407c is a zeotropic blend. As we discussed, this means that the refrigerants in this blend will boil separately.
Leaks
When a system that contains refrigerant blends is leaking, the refrigerant will leak at different
rates. This is because of the different vapor pressures of the refrigerants present in the blend.
Charging Blends
Refrigerant blends need to be charged as a liquid to get the full blend. Since refrigerant blends can experience fractionation, charging as a liquid ensures that we get the correct ratio of all the components.
You can think of this fractionation as orange juice with pulp. The pulp settles down to the bottom of the container when you leave it in the fridge. If you want the pulp to be evenly distributed, you would shake the container.
We don’t want to shake the container of refrigerant, because it is pressurized after all. But we do want to charge it as a liquid so we get the full blend of different refrigerants.
In this module, we discussed the properties of different refrigerant blends.
Retrofitting Systems
In this module, we will define the term ‘retrofitting’ and explain how existing refrigeration equipment can be retrofitted to operate on new refrigerant blends.
Replacing R-22
R-407c is a refrigerant blend of three HFC refrigerants — R-32, R-125, and R-134a.
R-407c was developed in order to replace R-22, an HCFC refrigerant. As we discussed before, refrigerant blends were created to replace refrigerants that were phased out, like HCFC.
Even though R-407c is generally the best replacement for R-22, there are limitations.
So how can we use the refrigerant blend R-407c in an R-22 system?
The answer is retrofitting. Existing refrigeration equipment can be retrofitted to operate on new refrigerant blends. Retrofitting is when we adapt and make changes to equipment so that we can use new refrigerant in it.
Refrigerant blends were designed to have the same properties as the original refrigerants. Technicians must follow guidelines on which blends a system can be retrofitted to operate on.
Drop-In Replacement
A drop-in refrigerant is a substitute refrigerant that has the same exact properties as the original refrigerant. No retrofitting is necessary for a drop-in refrigerant.
There are currently no drop-in refrigerants substitutes for R-22. All systems with R-22 must be retrofitted to operate on other refrigerants.
If we top off the system, we are also mixing the refrigerants. This makes both refrigerants impossible to reclaim. It also give us unpredictable temperatures, as we discussed before.
Using a different refrigerant may also void manufacturer warranties, if it operates outside of their guidelines.
In this module, we discussed how to retrofit existing refrigeration equipment to operate on new refrigerant blends.
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