3.8 - Quick Reference

Module: Refrigerants Blends and Lubricants
Covers: Sections 3.1–3.7
Technical and regulatory verification date: August 7, 2026
Use: Rapid review before the Module 3 practice questions and later Core/Universal certification review

1. Refrigerant Properties and Phase Change

Heat-Transfer Role

Pressure and Saturation

For a given refrigerant:

Higher saturation pressure
→ higher saturation temperature

Lower saturation pressure
→ lower saturation temperature

Reducing pressure can cause a liquid refrigerant to boil because its saturation temperature decreases.

Phase Identification

At saturation, pressure and temperature alone do not tell whether the refrigerant is saturated liquid, saturated vapor, or a two-phase mixture.

High-Priority Memory Aid

Evaporator → refrigerant absorbs heat
Condenser  → refrigerant rejects heat

2. Pure Refrigerants and Refrigerant Blends

Refrigerant / Blend Type Summary

Series Reminder

400 series → zeotropic blends
500 series → azeotropic blends

Do not overgeneralize:

• A 400-series blend does not necessarily have a large glide.
• A near-azeotropic blend does not become a 500-series refrigerant because its glide is small.
• An azeotrope is still a blend containing multiple chemical components.

Fractionation

Fractionation is a change in blend composition caused by preferential separation or loss of components.

Fractionation can occur because:

• Liquid and vapor phases of a zeotrope can have different compositions.
• A leak can preferentially remove one phase or component.
• Vapor withdrawal from a supply cylinder can change the remaining blend composition.

Fractionation is not the same as temperature glide.

3. Bubble Point Dew Point and Temperature Glide

Core Definitions

For a typical zeotropic blend at one pressure:

$$\text{Glide}=T_{\text{dew}}-T_{\text{bubble}}$$

and:

Tdew > Tbubble

Evaporation and Condensation

During evaporation:

Bubble point
→ two-phase region
→ Dew point

During condensation:

Dew point
→ two-phase region
→ Bubble point

Technician Reference

Superheat  → use Dew
Subcooling → use Bubble

Memory aid:

Dew    = vapor side
Bubble = liquid side

Important Limits

• Do not automatically average bubble and dew temperatures.
• Use the correct P-T data for the specific refrigerant.
• Confirm whether the table uses gauge pressure or absolute pressure.
• Pressure alone does not identify an unknown refrigerant.
• Small glide does not mean zero glide.

4. Liquid-Charging Reminder for Refrigerant Blends

Zeotropic Supply-Cylinder Withdrawal

Withdraw a zeotropic refrigerant blend from the supply cylinder as liquid to help preserve its specified composition.

Reason:

Zeotropic liquid and vapor compositions can differ
→ vapor-only withdrawal can change composition
→ liquid withdrawal helps preserve the intended blend

Liquid Withdrawal Does Not Mean Liquid Slugging

Do not confuse:

Withdraw blend from supply cylinder as liquid

with:

Allow uncontrolled liquid into a running compressor

When charging through the low side of an operating system:

• Meter the refrigerant as required.
• Allow it to vaporize before reaching the compressor when the approved procedure requires it.
• Follow the equipment and refrigerant charging procedure.

Recovery Is Different From Charging

During recovery:

• Capture the complete remaining blend.
• Do not intentionally separate blend components.
• Do not recover different refrigerants into the same cylinder.
• Recovery does not reverse fractionation that already occurred before recovery.

5. Refrigerant Identification

Identification Sequence

Equipment nameplate / retrofit label
→ cylinder label
→ service history
→ P-T consistency check
→ refrigerant analyzer if needed

Identification Sources

Cylinder Color

Cylinder color alone is not sufficient refrigerant identification.

Color cannot prove:

• Refrigerant identity.
• Purity.
• Whether the cylinder has been reused.
• Whether refrigerants have been mixed.

Read the label.

P-T Identification Limitation

A meaningful P-T check requires:

• Pressure.
• Temperature.
• Correct refrigerant P-T data.
• Suitable equilibrium conditions.

A matching P-T point is supporting evidence, but:

P-T behavior does not prove refrigerant purity.

Pressure alone is not sufficient because:

• Pressure changes with temperature.
• Different refrigerants can have similar pressures.
• Zeotropic blends require bubble/dew interpretation.
• Noncondensables can alter pressure.
• Operating pressure is not the same as a static equilibrium test.

Unknown or Mixed Refrigerant

If identity is uncertain:

Stop
→ verify
→ analyze if needed
→ isolate suspect refrigerant
→ do not mix with known refrigerant

Accidentally mixing two refrigerants does not create a properly formulated commercial blend.

6. Refrigerant Lubricants

Major Lubricant Families

These are broad exam-preparation associations, not universal substitution rules.

Lubricant Properties

Oil Return

Poor refrigerant-lubricant behavior can cause:

Oil trapped in system
→ reduced oil return
→ compressor oil starvation
→ wear / failure

Excessive refrigerant dissolved in the oil can also thin the lubricant and weaken the oil film.

Moisture-Sensitive Oils

POE and PAG require special moisture control:

Keep sealed
Keep clean
Keep dry
Minimize exposure to air

Lubricant Selection Rule

Refrigerant
+
compressor
+
lubricant chemistry
+
viscosity grade
+
system design

must be compatible.

The compressor or equipment manufacturer’s specification controls actual lubricant selection.

7. Moisture Acid and Noncondensables

Contamination Effects

Moisture Damage Sequence

Moisture
→ chemical degradation
→ acid / corrosion
→ copper movement or plating
→ compressor damage

Moisture can also freeze at:

• Capillary tubes.
• Expansion-valve passages.
• Small orifices.

Noncondensables

Common examples:

• Air.
• Nitrogen left after pressure testing.

In the condenser:

Noncondensable gas remains gaseous
→ adds pressure
→ interferes with condensation
→ head/discharge pressure can increase

High head pressure does not prove noncondensables. Dirty condensers, low airflow, high ambient temperature, overcharge, and other conditions can also raise head pressure.

Filter-Drier

A filter-drier:

• Removes moisture.
• Filters solid particles.
• Uses a desiccant.
• Has limited moisture capacity.

It does not remove air from the system.

Moisture Indicator

A moisture-indicating sight glass:

• Indicates moisture condition.
• Does not remove moisture.
• Must be interpreted according to the manufacturer’s color legend.

Do not memorize one universal color code for every moisture indicator.

Deep Evacuation

Deep evacuation removes:

• Air.
• Other noncondensable gases.
• Water vapor.

Vacuum lowers the boiling temperature of water:

Lower absolute pressure
→ lower water boiling temperature
→ water vaporizes
→ vacuum pump removes vapor

Deep-Vacuum Measurement

• Use a micron gauge for deep-vacuum measurement.
• A compound gauge in inches of mercury does not provide adequate resolution in the deep-vacuum range.
• This course uses 500 microns as a common service/dehydration benchmark.
• 500 microns is not the universal EPA refrigerant-recovery requirement for every appliance.

Important Vacuum Warnings

• A filter-drier does not replace evacuation.
• Evacuation does not replace a filter-drier.
• A vacuum pump does not replace required refrigerant recovery.
• Nitrogen left in the system becomes a noncondensable.
• Do not energize a hermetic compressor under deep vacuum.
• Large amounts of water can freeze during rapid evacuation and slow dehydration.

8. Retrofitting and Substitute Refrigerants

Central Rule

There is no universal drop-in refrigerant replacement.

Do not select a substitute only because:

• Pressure appears similar.
• The refrigerant is marketed as a replacement.
• It has a lower GWP.
• The original refrigerant is expensive or unavailable.

Retrofit Compatibility Checklist

Before charging a substitute, verify:

Retrofit Sequence

Identify existing refrigerant
→ verify substitute for the end-use
→ obtain approved retrofit procedure
→ check equipment / lubricant / materials / safety
→ recover original refrigerant
→ make required changes
→ repair leaks
→ pressure-test
→ evacuate
→ charge by measured mass
→ verify operation
→ leak-check
→ label the retrofit

Leak Testing

Dry nitrogen is commonly used for pressure testing.

Do not use:

• Oxygen.
• Ordinary compressed air.

After testing:

Remove nitrogen
→ evacuate
→ verify vacuum
→ charge refrigerant

Nitrogen left in the system becomes a noncondensable.

Charging After Retrofit

• Do not assume the old refrigerant charge weight is correct.
• Charge by measured mass.
• Follow the approved replacement-refrigerant procedure.
• Withdraw zeotropic blends from the supply cylinder as liquid.
• Use the new refrigerant’s P-T data.
• Verify superheat/subcooling with the correct bubble/dew reference where applicable.

Labeling

After retrofit, clearly identify:

• New refrigerant.
• New lubricant when applicable.
• Charge information when required.
• Date and relevant retrofit information.

Do not leave the original refrigerant nameplate as the only current identification.

Current-Rule Reminder

A restriction on refrigerant used in new equipment does not automatically require every existing system to be retrofitted.

Existing equipment can generally continue to be serviced with legally available refrigerant when current rules permit.

For major reconstruction or conversion projects, verify the current requirements before proceeding.

9. High-Priority Module 3 Comparison Tables

Phase and Blend Comparison

Identification and Service Comparison

Lubricant and Contamination Comparison

10. Common Module 3 Exam Traps

11. Rapid Technician Decision Sequences

Refrigerant Identification

Nameplate / retrofit label
→ cylinder label
→ P-T consistency
→ analyzer if uncertain
→ isolate if suspect

Zeotropic Charging

Verify refrigerant
→ withdraw from cylinder as liquid
→ meter safely if charging low side
→ prevent liquid slugging

Contaminated System

Identify contamination
→ correct leak / source
→ replace required filter-drier
→ evacuate / dehydrate
→ verify vacuum
→ charge clean refrigerant

Retrofit

Verify substitute
→ verify equipment compatibility
→ recover old refrigerant
→ make required changes
→ leak-test
→ evacuate
→ charge by mass
→ verify operation
→ relabel

12. Important Module 3 Relationships

Temperature Glide

$$\text{Glide}=T_{\text{dew}}-T_{\text{bubble}}$$

at the same pressure.

Saturation and Phase

For a given pure refrigerant:

Higher pressure ↔ higher saturation temperature
Lower pressure  ↔ lower saturation temperature

Technician Bubble/Dew Rule

Superheat  → Dew
Subcooling → Bubble

Moisture Control

Keep system closed
+ keep lubricant dry
+ use filter-drier
+ deep evacuate

Retrofit Compatibility

Refrigerant
+ lubricant
+ compressor
+ materials
+ pressure rating
+ safety class
+ approved procedure

must work together.

13. Detailed-Section Links

• Section 3.1 - Refrigerant Properties and Phase Change
• Section 3.2 - Pure Refrigerants and Refrigerant Blends
• Section 3.3 - Temperature Glide Bubble Point and Dew Point
• Section 3.4 - Refrigerant Identification
• Section 3.5 - Refrigerant Lubricants
• Section 3.6 - Moisture Acid and Noncondensables
• Section 3.7 - Retrofitting and Substitute Refrigerants