Refrigerant Blends Explained: What Every Technician Needs to Know

Not all refrigerants are created equal. Some are simple, single-component chemicals like R-22, while others are blends of refrigerants designed to balance performance, efficiency, and environmental impact. Understanding these blends is critical for technicians, both for the EPA 608 Certification exam and real-world service work.

Single-Component Refrigerants

Before blends, let’s start with the basics. A single-component refrigerant has one boiling point. For example, R-22 boils at –41°F. This makes calculating superheat and subcooling straightforward:

• Superheat: Degrees above boiling point (in vapor).

• Subcooling: Degrees below the boiling point (in liquid).

That simplicity disappears when we move into blends.

Note: these are simplified charts that are not to scale.

Types of Refrigerant Blends

1. Azeotropic Blends

• Act like single-component refrigerants.

• No temperature glide (they boil and condense at a single temperature).

• Labeled in the 500 series (e.g., R-502).

• Easy to handle in the field since they behave predictably.

2. Zeotropic (Ternary) Blends

• Mixtures of two or more refrigerants with different boiling points.

• Labeled in the 400 series (e.g., R-407C).

• Exhibit temperature glide (a difference of 0.2°F–16°F).

  • Dew point = used for superheat.

  • Bubble point = used for subcooling.

• When sizing equipment, technicians often use the midpoint temperature.

3. Near-Azeotropic Blends

• Behave mostly like a single refrigerant, but can separate slightly.

• Example: R-410A (blend of R-32 and R-125).

• Minimal glide, but fractionation is still possible if leaks occur.

Fractionation: Why It Matters

Fractionation occurs when different components of a blend leak at different rates. This can alter the refrigerant’s composition, reducing efficiency and potentially damaging the system.

• Example: If the lighter component leaks out first, the remaining refrigerant no longer matches the performance specs on the PT chart.

• Best practice: Always charge zeotropic blends in liquid form to minimize fractionation.

Key Takeaways for Technicians

• Know your blend type: Azeotropic, zeotropic, or near-azeotropic.

• Watch for glide: Zeotropic blends require using bubble and dew points correctly.

• Prevent fractionation: Always charge blends as liquid, never vapor.

• On the exam: Expect questions about temperature glide, fractionation, and blend identification numbers.

Pro Tip

When working with R-407C, always remember:

• Use the dew point column on your PT chart for superheat.

• Use the bubble point column for subcooling.

This is one of the most common test questions — and one of the most common mistakes in the field.