3.6 - Moisture Acid and Noncondensables

Technical source review date: August 7, 2026
Primary technical basis: Current project Module 3 outline, EPA Section 608 study guidance, HVAC licensing study guidance, and refrigeration service fundamentals used throughout this project
Course role: Explains how moisture, acids, and noncondensable gases damage refrigeration systems and how filter-driers, moisture indicators, and deep evacuation are used to control contamination

Learning Objectives

After completing this section, a student should be able to:

1. Explain how moisture enters a refrigeration system and why it is harmful.
2. Describe how moisture and system contamination can contribute to acid formation, corrosion, copper plating, and compressor damage.
3. Explain why noncondensable gases increase condensing pressure and reduce system performance.
4. Describe the purposes and limitations of filter-driers and moisture-indicating sight glasses.
5. Explain how deep evacuation removes air and water vapor and why a micron-level vacuum measurement is preferred.
6. Apply a technician-level contamination-control sequence before a system is returned to service.

Introduction

A refrigeration system is intended to contain:

• The correct refrigerant.
• The correct lubricant.
• Clean internal surfaces.
• As little moisture and noncondensable gas as practical.

When air, water, acids, dirt, burned oil, or other contaminants enter the system, the refrigeration cycle can still appear to operate, but the system may experience:

• Higher condensing pressure.
• Reduced heat transfer.
• Restricted metering devices.
• Corrosion.
• Lubricant breakdown.
• Electrical insulation damage.
• Compressor wear or failure.

The current Module 3 outline requires special attention to:

• Moisture contamination.
• Acid formation.
• Copper plating and compressor damage.
• Noncondensables.
• Increased head pressure.
• Filter-driers.
• Moisture indicators.
• Deep evacuation.

The most important technician principle is:

Contamination should be prevented whenever possible. Once contamination is inside a sealed refrigeration system, removing it is more difficult than keeping it out.

Key Concepts

1. The Refrigeration Circuit Should Remain Clean, Dry, and Sealed

A properly prepared refrigeration system should contain only the materials intended by the equipment manufacturer.

Unwanted materials include:

• Water.
• Air.
• Nitrogen left from pressure testing.
• Dirt.
• Metal particles.
• Burned oil residue.
• Acids.
• Incorrect refrigerant.
• Incorrect lubricant.

Contaminants can enter when:

• Tubing or components are left open to the atmosphere.
• Hoses or tools contain air or moisture.
• Refrigerant or oil containers are left open.
• A leak allows air and moisture to enter.
• A system is pressure-tested and the test gas is not removed.
• A compressor burnout contaminates the circuit.
• Service equipment is not clean or properly prepared.

For refrigerant-identification and cross-contamination practices, see Section 3.4 - Refrigerant Identification.

For lubricant moisture sensitivity, see Section 3.5 - Refrigerant Lubricants.

2. Moisture and Noncondensables Are Different Problems

Both can enter with atmospheric air, but their effects are different.

A system may contain more than one type of contamination at the same time.

Moisture Contamination

1. How Moisture Enters the System

Moisture can enter when:

• The sealed system is opened to humid air.
• New tubing or components are stored uncapped.
• Service hoses contain humid air.
• Refrigeration oil absorbs moisture.
• A leak allows air to enter a system operating below atmospheric pressure.
• Wet nitrogen, compressed air, or contaminated service gas is introduced.
• Components are installed while internally wet.

Moisture control begins before evacuation.

Good service practice includes:

Keep tubing capped
Keep lubricant containers closed
Use dry service gases
Use clean, dry tools
Minimize time open to atmosphere
Evacuate after the system is sealed

2. Why Moisture Is Harmful

Moisture can produce several problems.

Chemical Damage

Water can participate in or accelerate chemical reactions involving:

• Refrigerant.
• Lubricant.
• High temperature.
• Metal surfaces.
• Burnout contaminants.

The result can include acidic compounds and lubricant degradation.

Corrosion

Moisture and acids can attack metal surfaces.

Possible results include:

• Corrosion products.
• Metal contamination.
• Reduced component life.
• Damage to compressor parts.

Ice Formation

Water can freeze at a cold restriction.

A small amount of ice can partially or completely block:

• Capillary tube.
• Expansion-valve passage.
• Small orifice.

The restriction may appear intermittent because the ice can melt when the system warms and refreeze when the system cools.

Electrical Damage

Moisture and acidic contamination can reduce the electrical insulating quality of refrigerant oil.

This is especially important in:

• Hermetic compressors.
• Semi-hermetic compressors.

where motor windings operate inside the refrigerant-oil environment.

3. Moisture Can Be Free or Dissolved

Not all water behaves the same way.

Moisture may exist as:

• Free liquid water.
• Water vapor.
• Moisture dissolved or absorbed in lubricant.
• Moisture held by desiccant.

Free water can be relatively easy to vaporize under vacuum.

Moisture absorbed into a hygroscopic lubricant such as polyolester (POE) can be harder to remove.

This is why:

A deep vacuum is important, but evacuation cannot always reverse severe lubricant contamination.

Severely contaminated oil may require:

• Oil replacement.
• Filter-drier replacement.
• Burnout cleanup.
• Additional dehydration procedures.

The correct procedure depends on the equipment and contamination severity.

Acid Formation

1. Acid Is a Result of Chemical Contamination

Acid formation is not simply:

water + any refrigerant = acid

The actual chemistry depends on:

• Refrigerant.
• Lubricant.
• Temperature.
• Moisture level.
• Decomposition products.
• Compressor burnout.
• Metals and contaminants present.

A useful technician-level relationship is:

Moisture + heat + refrigerant/lubricant contamination
→ chemical breakdown can accelerate
→ acidic products can form

2. Older Halogenated Refrigerants

Older HVAC references describe hydrolysis reactions in which water reacts with certain halogenated refrigerants or their decomposition products and acidic materials form.

The practical lesson is:

Moisture and heat should not be allowed to remain in a refrigeration system.

3. POE and Moisture

POE lubricant is especially hygroscopic.

Moisture in an ester lubricant can contribute to hydrolytic degradation and formation of acidic products.

Therefore:

• Keep POE containers closed.
• Do not leave the system open unnecessarily.
• Use proper dehydration procedures.
• Replace contaminated lubricant when required.

4. Compressor Burnout

A severe electrical or mechanical compressor failure can expose:

• Refrigerant.
• Lubricant.
• Winding insulation.
• Metal.
• High temperatures.

to damaging conditions.

The result may include:

• Acid.
• Carbonized material.
• Sludge.
• Degraded oil.
• Metal debris.

Technicians should watch for oil contamination when a compressor burnout is suspected and apply additional cleanup measures such as filter-driers and deep evacuation.

Burnout cleanup must follow:

• Compressor-manufacturer procedure.
• Equipment-manufacturer procedure.
• Refrigerant and lubricant requirements.

Copper Plating and Compressor Damage

1. What Copper Plating Means

Copper plating is the deposition of copper onto surfaces where copper was not originally intended to coat the part.

In a contaminated refrigeration system, acidic conditions can attack copper tubing and dissolve copper into the circulating refrigerant-oil mixture.

Under suitable chemical and temperature conditions, copper can later deposit onto steel compressor surfaces.

A simplified technician-level sequence is:

Moisture / acid contamination
→ copper is attacked
→ copper enters circulating fluid
→ copper deposits on compressor surfaces
→ clearances and lubrication can be affected

2. Why Copper Plating Is Harmful

Copper deposited on compressor parts can contribute to:

• Bearing damage.
• Scoring.
• Tight clearances.
• Valve problems.
• Increased friction.
• Premature compressor failure.

Copper plating is therefore evidence of a deeper contamination problem, not merely a cosmetic discoloration.

3. Acid Can Damage More Than Metal

Acid contamination can also damage:

• Motor-winding insulation.
• Lubricant.
• Elastomers.
• Seals.
• Internal compressor coatings.

The technician should not treat acid as a localized problem.

If acid or burnout contamination is present, the entire refrigerant-oil circuit may require cleanup.

Noncondensable Gases

1. Definition

A noncondensable gas is a gas that does not condense into liquid under the normal condenser temperature and pressure conditions of the refrigeration system.

In ordinary HVAC service, the most common noncondensable contaminant is:

Air.

Nitrogen can also become a noncondensable contaminant if it is left in the system after pressure testing.

2. How Noncondensables Enter

Noncondensables can enter when:

• A system is opened.
• Hoses are not properly prepared.
• Air is trapped during charging.
• A below-atmospheric-pressure system leaks inward.
• Nitrogen remains after pressure testing.
• A poor evacuation leaves residual gas.

3. Why Noncondensables Collect in the Condenser

The refrigerant vapor condenses in the condenser.

Air and other noncondensables do not condense under the same operating conditions.

They therefore tend to remain in the vapor space, especially in the condenser and receiver regions where refrigerant is condensing.

This creates two important effects:

1. Additional gas pressure.
2. Reduced effective condenser heat-transfer area.

Increased Head Pressure

1. Noncondensables Raise Total Condensing Pressure

The pressure measured in the condenser can include contributions from:

• Refrigerant vapor.
• Noncondensable gas.

At technician level:

Refrigerant vapor pressure
+
noncondensable-gas pressure
=
higher total head pressure

Noncondensables cause higher discharge pressures.

2. Reduced Condenser Effectiveness

Noncondensables can occupy part of the condenser volume and form a gas-rich region that interferes with refrigerant condensation.

Possible results include:

• Higher condensing pressure.
• Higher compressor discharge temperature.
• Increased compressor power.
• Reduced capacity.
• High-pressure safety trips.
• Compressor stress.

3. High Head Pressure Does Not Prove Noncondensables

High head pressure can also be caused by:

• Dirty condenser coil.
• Restricted condenser airflow.
• High outdoor temperature.
• Overcharge.
• Restricted condenser-water flow.
• High entering condenser-water temperature.
• Improper condenser control.

Therefore:

Noncondensables are one possible cause of high head pressure, not the only cause.

The complete operating condition must be evaluated.

4. Pressure-Temperature Clue

A technician may suspect noncondensables when:

• Refrigerant identity is known.
• The system or isolated sample is at a known temperature.
• The measured pressure is higher than the expected refrigerant saturation pressure.
• Other causes have been considered.

However, a single pressure reading does not by itself prove noncondensables.

For refrigerant identification limitations, see Section 3.4.

Filter-Driers

1. Purpose

A filter-drier combines two major functions:

1. Filtering — captures solid contaminants.
2. Drying — removes moisture using a desiccant.

Depending on design, a filter-drier may also help control:

• Acid.
• Decomposition products.
• Burnout contaminants.

2. Desiccant

The drying material inside the filter-drier is called a desiccant.

Common desiccant technologies are selected to:

• Adsorb moisture.
• Remain compatible with refrigerant and lubricant.
• Avoid releasing captured moisture under normal use.

The technician does not normally service or regenerate the internal desiccant in the field.

The drier is replaced as a component.

3. Filter-Drier Capacity Is Limited

Filter-driers can remove moisture but have a limited capacity.

Once the desiccant becomes saturated:

• It cannot continue removing moisture effectively.
• The system may still contain excessive water.

Therefore:

A filter-drier does not replace proper evacuation.

Likewise:

Evacuation does not eliminate the need for a filter-drier where the system design requires one.

4. Replacement After Opening the System

The filter-drier should be replaced when the sealed refrigeration system is opened for servicing.

For field practice, follow the equipment or compressor manufacturer’s procedure, especially when:

• The drier has been exposed to atmosphere.
• Moisture contamination is suspected.
• The drier is restricted.
• A compressor burnout occurred.
• A retrofit requires a new drier.

5. Liquid-Line and Suction-Line Filter-Driers

A liquid-line filter-drier is common in many systems.

A suction-line filter-drier may be used temporarily or as specified during:

• Compressor burnout cleanup.
• Acid removal.
• Severe contamination cleanup.

A suction-line drier creates pressure drop and must be used, monitored, and removed or left in place only according to the approved procedure.

Moisture Indicators

1. Moisture-Indicating Sight Glass

Some refrigeration systems use a sight glass that includes a chemical moisture indicator.

The indicator changes appearance as moisture condition changes.

A moisture-indicating sight glass can help show whether the refrigerant/oil circuit is:

• Dry enough for the indicator range.
• Showing elevated moisture.
• Changing after a drier replacement or dehydration procedure.

2. Do Not Memorize One Universal Color

Different moisture indicators may use different:

• Color scales.
• Moisture thresholds.
• Refrigerant-specific ratings.

Therefore:

Read the indicator manufacturer’s legend.

Do not assume that one color means “dry” for every product.

3. A Moisture Indicator Does Not Replace Evacuation

A moisture indicator:

• Does not remove water.
• Does not remove air.
• Does not remove acid.
• Does not clean the refrigerant.

It is an indicator, not a treatment device.

4. Indicator Response May Take Time

After:

• Evacuation.
• Drier replacement.
• System charging.

the refrigerant and lubricant may need time to circulate and reach the moisture indicator.

Do not assume that the indicator must change immediately.

Follow the component manufacturer’s interpretation procedure.

Deep Evacuation

1. Purpose

A deep evacuation is used to remove:

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

after the refrigerant has been properly recovered and the system has been sealed for evacuation.

Deep evacuation is a dehydration procedure.

It is not a substitute for refrigerant recovery.

2. Why Vacuum Removes Moisture

Reducing pressure lowers the boiling temperature of water.

Under a sufficiently deep vacuum:

• Liquid water can boil at a much lower temperature.
• Water changes into vapor.
• The vacuum pump removes that vapor.

A simplified sequence is:

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

This is why a vacuum pump can dehydrate a sealed system.

3. Deep Vacuum Is Measured in Microns

Service guidance in this course uses a vacuum pump capability of 500 microns and identifies microns as the preferred method for measuring a deep vacuum.

For this project, treat 500 microns as a study-guide/service benchmark, not as a universal federal evacuation requirement for every appliance.

The detailed EPA-required refrigerant recovery/evacuation levels are separate regulatory requirements and are developed later in Modules 5, 8, and 9.

4. Why Inches of Mercury Are Poor for Deep Vacuum

A conventional compound gauge can show a reading near:

29 inches Hg vacuum

but small changes in deep vacuum are difficult to distinguish on that scale.

A micron gauge is much more sensitive in the deep-vacuum range.

Therefore:

Use a micron gauge for dehydration-level vacuum measurement.

5. Vacuum Pump Capacity and System Dehydration Are Not the Same

A vacuum pump may be capable of reaching a very low pressure at its inlet, yet the system may not reach the same vacuum because of:

• Leaks.
• Moisture boiling.
• Restricted hoses.
• Schrader cores.
• Closed valves.
• Large system volume.
• Contaminated vacuum-pump oil.

Therefore, verify vacuum at the system, not only at the pump.

6. Large-Diameter Vacuum Hoses Improve Evacuation Speed

Evacuation is a low-pressure gas-flow process.

Restrictions reduce evacuation speed.

Good evacuation practice commonly includes:

• Large-diameter vacuum-rated hoses.
• Short hose lengths where practical.
• Core-removal tools where appropriate.
• A clean vacuum pump.
• Fresh vacuum-pump oil.
• A micron gauge connected where it can represent system pressure.

Detailed service-tool setup is developed in Module 5.

7. Vacuum Decay / Standing Vacuum Check

After reaching the desired deep vacuum:

1. Isolate the vacuum pump.
2. Observe system pressure with the micron gauge.
3. Evaluate whether pressure rises.

A pressure rise can indicate:

• A leak.
• Remaining moisture.
• Refrigerant still trapped in oil.
• Outgassing from internal materials.

The shape and amount of pressure rise must be interpreted according to the service procedure and system.

Do not assume every small rise proves a leak.

8. Large Amounts of Water Can Freeze

Pulling a vacuum rapidly on a system containing a large amount of water can cause the water to freeze.

Why?

Water boils under vacuum
→ evaporation removes heat
→ remaining water cools
→ water can freeze

Ice has a much lower vaporization rate than liquid water and can slow dehydration.

When major moisture contamination exists, approved procedures may use:

• Controlled warming.
• Dry nitrogen between evacuation stages.
• Multiple evacuation stages.

Only dry nitrogen should be used for this purpose, and the refrigerant must already have been properly recovered.

9. Do Not Energize a Hermetic Compressor Under Deep Vacuum

Do not energize a hermetic compressor motor under deep vacuum.

A deep vacuum can reduce the electrical insulating strength of the gas environment and increase the risk of electrical arcing or motor-winding damage.

Therefore:

Do not run a hermetic compressor to “help” pull a deep vacuum.

Use the vacuum pump.

Evacuation and Filter-Drier Work Together

A clean system preparation strategy is:

Repair and seal system
↓
Replace required filter-drier
↓
Connect clean vacuum equipment
↓
Deep evacuate
↓
Verify with micron gauge
↓
Isolate and evaluate vacuum stability
↓
Charge with correct refrigerant
↓
Monitor moisture indicator if installed

This sequence is a teaching framework.

Actual service order can vary with:

• Equipment design.
• Burnout cleanup.
• Retrofit procedure.
• Manufacturer instructions.

Contamination-Control Decision Table

Technical Details

1. Air Adds Pressure Without Adding Useful Refrigeration

Air in the condenser:

• Does not provide useful refrigerating effect.
• Does not condense like the refrigerant.
• Adds pressure.
• Interferes with heat transfer.

This is why noncondensables increase compressor work rather than capacity.

2. Moisture Can Produce Both Mechanical and Chemical Problems

Mechanical effect:

Water freezes at a restriction
→ refrigerant flow decreases

Chemical effect:

Moisture participates in degradation
→ acids / corrosion / copper movement

A technician should therefore not think of moisture only as an “ice problem.”

3. Filter-Drier Does Not Remove Noncondensable Gas

A filter-drier can remove:

• Moisture.
• Particles.
• Some chemical contaminants depending on design.

It does not remove air from the system.

Air is removed by:

• Proper evacuation.
• Appropriate purge procedures in systems designed for purging.

4. Vacuum Pump Does Not Replace a Filter-Drier

A vacuum pump removes gas and water vapor.

It does not:

• Filter metal particles.
• Capture sludge.
• Neutralize every acid.
• Remove all moisture already chemically or strongly absorbed into oil.

Filter-drier and evacuation have different functions.

5. Nitrogen Is Not a Refrigerant-Circuit “Cleaner” by Itself

Dry nitrogen can be useful for:

• Pressure testing.
• Sweeping during brazing.
• Breaking a vacuum during staged dehydration where specified.

But nitrogen left in the system becomes a noncondensable contaminant.

After pressure testing or nitrogen-assisted dehydration:

The nitrogen must be removed before final charging.

Important Terms

Acid

An acid is a corrosive chemical contaminant that can form from refrigerant, lubricant, moisture, heat, and decomposition reactions and can damage system materials.

Copper Plating

Copper plating is the unintended deposition of copper onto compressor or other metal surfaces as part of a contamination/corrosion process.

Deep Evacuation

Deep evacuation is the process of reducing a sealed refrigeration system to a low absolute pressure to remove air, noncondensables, and water vapor before charging.

Desiccant

A desiccant is a drying material used in a filter-drier to adsorb moisture.

Filter-Drier

A filter-drier is a refrigerant-system component that filters solid contaminants and removes moisture using a desiccant.

Head Pressure

Head pressure is a common technician term for the high-side or condensing pressure of a refrigeration system.

Micron

A micron of mercury is a unit used to express very low absolute pressure during deep evacuation.

Moisture Indicator

A moisture indicator is a chemical indicator, commonly incorporated into a sight glass, that changes appearance according to moisture condition.

Noncondensable Gas

A noncondensable gas is a gas that does not condense under the normal condenser operating conditions of the refrigeration system.

Vacuum Decay

Vacuum decay is the rise in absolute pressure observed after the vacuum pump is isolated from the system.

EPA 608 Exam Focus

What Students Must Remember

• Moisture is a major refrigeration-system contaminant.
• Moisture can contribute to:
  • Acid formation.
  • Corrosion.
  • Copper plating.
  • Lubricant degradation.
  • Ice at restrictions.
  • Compressor damage.
• POE and PAG lubricants are especially moisture sensitive.
• Air is the most common noncondensable contaminant.
• Noncondensables cause higher discharge/head pressure.
• High head pressure has other possible causes; do not assume noncondensables from pressure alone.
• Filter-driers:
  • Remove moisture.
  • Filter particles.
  • Have limited moisture capacity.
• A moisture-indicating sight glass indicates moisture condition; it does not remove moisture.
• Do not memorize one universal sight-glass color; read the manufacturer’s legend.
• Deep evacuation removes:
  • Air.
  • Noncondensables.
  • Water vapor.
• A micron gauge is preferred for measuring deep vacuum.
• A common service benchmark is that the vacuum pump should be capable of reaching 500 microns.
• Treat 500 microns here as a study-guide/service benchmark, not as the EPA regulatory recovery level for every appliance.
• Deep evacuation and filter-driers perform different jobs.
• A vacuum pump should not be used as a substitute for required refrigerant recovery.
• Do not energize a hermetic compressor while it is under a deep vacuum.
• A large amount of water can freeze during rapid evacuation and slow dehydration.
• Nitrogen left in a system becomes a noncondensable.

Typical Exam Question Patterns

Students may be asked to:

• Identify moisture as a cause of acid and compressor damage.
• Identify moisture as a cause of ice at a restriction.
• Identify noncondensables as a cause of high head pressure.
• Identify air as the common noncondensable contaminant.
• State the purpose of a filter-drier.
• Recognize that filter-drier capacity is limited.
• State the purpose of a moisture-indicating sight glass.
• Identify microns as the preferred deep-vacuum measurement.
• Explain why a deep vacuum helps remove moisture.
• Recognize that a hermetic compressor should not be operated under deep vacuum.
• Distinguish noncondensables from moisture contamination.
• Distinguish filter-drier function from vacuum-pump function.

High-Priority Contamination Table

Common Mistakes and Confusing Points

Mistake 1: Thinking Moisture Only Causes Ice

Moisture can also contribute to:

• Acid.
• Corrosion.
• Lubricant breakdown.
• Copper plating.
• Electrical damage.

Mistake 2: Assuming Every High Head Pressure Problem Is Noncondensables

Other causes include:

• Dirty condenser.
• Low airflow.
• High ambient temperature.
• Overcharge.
• Poor condenser-water flow.

Mistake 3: Thinking a Filter-Drier Removes Air

A filter-drier removes moisture and particles.

A vacuum procedure removes air and other noncondensable gases.

Mistake 4: Thinking a Vacuum Pump Replaces the Filter-Drier

Evacuation and filter-drying are complementary processes.

Mistake 5: Treating a Moisture Indicator as a Dryer

A moisture indicator detects a condition; it does not correct it.

Mistake 6: Memorizing One Sight-Glass Color for Every Product

Indicator colors and thresholds vary by manufacturer.

Read the legend.

Mistake 7: Assuming 500 Microns Is the EPA Recovery Requirement for Every Appliance

This course uses 500 microns as a deep-vacuum pump/service benchmark.

EPA refrigerant recovery/evacuation requirements use separate appliance-specific regulatory levels discussed later in the course.

Mistake 8: Measuring Deep Vacuum Only With a Compound Gauge

A micron gauge gives much better resolution in the deep-vacuum range.

Mistake 9: Leaving Nitrogen in the System After Pressure Testing

Nitrogen becomes a noncondensable contaminant if left in the circuit.

Mistake 10: Energizing a Hermetic Compressor Under Deep Vacuum

Use the vacuum pump for evacuation.

Do not operate the hermetic compressor in deep vacuum.

Concept-Check Questions

Question 1

Which problem can moisture cause in a refrigeration system?

A. Ice formation at a small refrigerant restriction

B. Permanent elimination of compressor friction

C. Lowering every system pressure to zero

D. Converting a zeotropic refrigerant into an azeotrope

Question 2

Which statement best describes acid formation in a contaminated refrigeration system?

A. Any refrigerant forms acid immediately whenever it contacts one molecule of water.

B. Moisture, heat, lubricant, refrigerant, and decomposition products can participate in chemical reactions that produce acidic contamination.

C. Acid can form only outside the sealed refrigeration circuit.

D. Acid is produced only by nitrogen pressure testing.

Question 3

Why is copper plating a concern in a contaminated refrigeration system?

A. Copper deposited on compressor surfaces can interfere with clearances and lubrication.

B. Copper plating increases the refrigerant’s latent heat.

C. Copper plating automatically removes acid from the system.

D. Copper plating improves bearing lubrication.

Question 4

What is a common effect of noncondensable gases in the condenser?

A. Lower head pressure in every operating condition

B. Elimination of compressor discharge heat

C. Higher condensing or discharge pressure

D. Conversion of refrigerant vapor directly into ice

Question 5

What is the primary purpose of a filter-drier?

A. To measure compressor motor current

B. To filter solid contaminants and remove moisture

C. To identify an unknown refrigerant by color

D. To remove all air without a vacuum pump

Question 6

Which statement about a moisture-indicating sight glass is correct?

A. It removes moisture as refrigerant flows through it.

B. Its color meaning is identical for every manufacturer.

C. It indicates moisture condition but does not itself dry the system.

D. It replaces the need for a filter-drier.

Question 7

Why is a micron gauge preferred when evaluating a deep vacuum?

A. It identifies refrigerant composition directly.

B. It provides much better resolution at very low absolute pressures.

C. It measures only high-side refrigerant pressure.

D. It eliminates the need for a vacuum pump.

Question 8

A refrigeration system was pressure-tested with dry nitrogen. What must happen before final refrigerant charging?

A. Leave the nitrogen in the system to reduce head pressure.

B. Convert the nitrogen into refrigerant with a filter-drier.

C. Remove the nitrogen during proper evacuation so it does not remain as a noncondensable.

D. Add more nitrogen until the moisture indicator changes color.

Answers and detailed explanations will be provided in 3.10 - Answers and Explanations.md.

Section Summary

A clean refrigeration system should contain:

• Correct refrigerant.
• Correct lubricant.
• Minimal moisture.
• Minimal noncondensable gas.
• Minimal solid and chemical contamination.

Moisture can cause:

Moisture
→ ice at restrictions
→ chemical degradation
→ acid
→ corrosion / copper plating
→ compressor damage

Noncondensables can cause:

Air or nitrogen
→ remains gaseous in condenser
→ adds pressure and reduces effective heat transfer
→ higher head/discharge pressure
→ greater compressor load

Filter-driers:

• Remove moisture.
• Capture particles.
• Have limited capacity.

Moisture indicators:

• Show moisture condition.
• Do not remove moisture.

Deep evacuation:

• Removes air and water vapor.
• Lowers the boiling temperature of water.
• Should be evaluated with a micron gauge.
• Must not be confused with refrigerant recovery.

This course uses 500 microns as a deep-vacuum pump/service benchmark and emphasizes that microns are the preferred measurement for deep vacuum.

The detailed EPA regulatory evacuation levels are addressed later in the recovery and Type-specific modules.

The next section addresses how these contamination and compatibility concerns affect refrigerant retrofit decisions.

See Section 3.7 - Retrofitting and Substitute Refrigerants.

References

Project Source

1. Current EPA Section 608 teaching-material project outline, Module 3 — Refrigerants Blends and Lubricants, Section 3.6. Required scope: moisture contamination, acid formation, copper plating and compressor damage, noncondensables, increased head pressure, filter-driers, moisture indicators, and deep evacuation. Reviewed August 7, 2026.

2. project_rules.md, current EPA 608 project subsection structure, source hierarchy, and quality-control requirements, reviewed August 7, 2026.

EPA Section 608 Teaching Source

3. International Training Institute for the Sheet Metal and Air Conditioning Industry, EPA Section 608 Study Guide, refrigeration notes and recovery/service sections. The guide states that filter-driers remove moisture but have limited capacity, describes moisture-indicating sight glasses, identifies microns as the preferred deep-vacuum measurement, gives 500 microns as a vacuum-pump capability benchmark, warns against energizing a hermetic compressor under deep vacuum, and identifies noncondensables as a cause of higher discharge pressure.

4. International Training Institute for the Sheet Metal and Air Conditioning Industry, EPA Section 608 Study Guide, service and maintenance discussion of compressor burnout cleanup, filter-driers, deep evacuation, and system contamination.

HVAC Technical Reference

5. Rex Miller and Mark R. Miller, HVAC Licensing Study Guide, 3rd ed., Chapter 10 — Maintenance, Servicing, and Safety, including filter-drier and contaminated-system service material.

6. Rex Miller and Mark R. Miller, HVAC Licensing Study Guide, 3rd ed., glossary entry on hydrolysis and related refrigeration-system contamination concepts.