10.4 Type III Leak Testing

EPA 608 Technician Certification Exam

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1 Introduction to EPA 608 Certification

1.1 What EPA 608 Is and Who Needs It 1.2 Exam Format, Scoring, and Administration 1.3 How to Study for EPA 608

2 Regulations and the Clean Air Act

2.1 Clean Air Act Overview 2.2 Penalties and Enforcement 2.3 Montreal Protocol and International Agreements 2.4 AIM Act and HFC Phasedown Schedule 2.5 SNAP Program and Refrigerant Transitions

3 Refrigerants and Ozone Science

3.1 The Science of Ozone Depletion (ODP and GWP) 3.2 Refrigerant Classification, ASHRAE Numbering, and Safety Groups 3.3 Common Refrigerants: Properties, Applications, and Phaseout Status 3.4 Refrigerant Blends: Glide, Fractionation, and Liquid Charging

4 The Refrigeration Cycle

4.1 The Basic Refrigeration Cycle 4.2 System Components in Detail 4.3 Heat Transfer and Pressure-Temperature Relationships

5 Refrigerant Safety and Handling

5.1 Refrigerant Hazards and Health Effects 5.2 Safe Handling Practices, PPE, and Cylinders 5.3 A2L (Mildly Flammable) Refrigerant Safety

6 Recovery, Recycling, and Reclaiming

6.1 The Three Rs: Recover, Recycle, Reclaim 6.2 Recovery Equipment Requirements 6.3 Required Levels of Evacuation 6.4 Refrigerant Sales Restrictions and Recordkeeping

7 Leak Detection and Repair

7.1 Leak Detection Methods 7.2 Leak Repair Requirements and Trigger Rates 7.3 Leak-Rate Calculation, Recordkeeping, and Reporting

8 Type I — Small Appliances

8.1 What Counts as a Small Appliance 8.2 Type I Recovery Requirements 8.3 Type I Procedures, Access Valves, and the Open-Book Exam

9 Type II — High-Pressure Appliances

9.1 What Type II Covers: High-Pressure System Overview 9.2 Type II Recovery Methods and Required Evacuation Levels 9.3 Leak Detection, the Repair Triggers, and Recordkeeping 9.4 The R-22 Phaseout, Retrofits, and the Move to Lower-GWP A2Ls

10 Type III — Low-Pressure Appliances

10.1 Low-Pressure System Fundamentals 10.2 Purge Units and Air Management 10.3 Type III Recovery and Procedures 10.4 Type III Leak Testing

11 10. Disposal, Shipping, and Compliance

11.1 Equipment Disposal Requirements 11.2 Refrigerant Shipping and Transport 11.3 Compliance Checklist and Best Practices

12 Final Review and Exam Strategy

12.1 High-Yield Core Section Review 12.2 Type I vs Type II vs Type III: Side-by-Side Review 12.3 How the Exam Works and Exam-Day Strategy

10.4 Type III Leak Testing

Key Takeaways Explain This Topic AI

Raise a low-pressure system's pressure for a leak test with controlled hot water or a built-in heating/pressurization device first, then dry nitrogen, staying below the rupture-disc rating

Add a small trace of refrigerant to the nitrogen so an electronic leak detector can find the leak — never pressurize with refrigerant alone

A standing-vacuum test pulls the machine to a deep vacuum, isolates it, and watches for pressure rise over time (often 24 hours)

In a standing-vacuum test, a steady pressure rise that then levels off usually signals moisture boiling off; a continuous rise signals an air leak

Tube and water-box leaks are critical: the vacuum pulls cooling water INTO the refrigerant, forming acid and copper plating

Last updated: October 2026

Leak Testing Without Blowing the Rupture Disc

Leak testing a low-pressure chiller is fundamentally a balancing act: you need enough pressure for a detector to find the leak, but a low-pressure machine cannot tolerate much pressure at all. The governing limit is the rupture disc , rated at the chiller's maximum working pressure (Trane, for example, rates the disc on its R-123 CenTraVac chillers at 15 psig ±2 psig). Stay within the manufacturer's leak-test limit, below that rating, so the disc does not blow during the test.

The Correct Pressurization Method

First choice: controlled hot water or a built-in heating/pressurization device (such as Prevac), which raises the refrigerant's own pressure — this is EPA's order of preference.

Second choice: dry nitrogen through a regulator with a relief valve — inert and moisture-free. Never use air or oxygen.

Stay below the rupture-disc rating and within the manufacturer's limit.

If nitrogen is used, add a small trace of refrigerant to the nitrogen so an electronic leak detector (or halide-style detector) can sense escaping refrigerant at the leak site. Pure nitrogen leaks silently — the trace gives the detector something to find.

Never pressurize with refrigerant alone. It is wasteful, costly, and venting it is a Section 608 violation; nitrogen does the pressurizing work and only a trace of refrigerant is needed.

A nitrogen-plus-trace test is a positive-pressure method; on a low-pressure machine EPA ranks it after the hot-water or built-in heating methods.

The Standing-Vacuum Test

Because a low-pressure system spends its life in a vacuum, the most telling integrity check is the standing-vacuum test (also called a vacuum decay or rate-of-rise test) . It checks the very thing that matters — whether the machine holds a vacuum:

Evacuate the system to a deep vacuum with a vacuum pump.

Isolate the pump (valve it off) so nothing is actively pulling.

Watch the micron gauge over time — often a 24-hour standing test.

Interpret the rise , which is the diagnostic art:

Observation Likely cause
Pressure holds steady at deep vacuum Tight system, no leak, dry
Pressure rises, then levels off and stops Moisture boiling off inside — needs more evacuation, not a leak hunt
Pressure rises continuously without leveling Air leak — atmosphere is bleeding in

The key exam nuance: a rise that plateaus points to trapped water vaporizing (continue dehydration), while a rise that never stops points to an actual air leak (find and seal it). This lets a technician separate a moisture problem from a leak problem without ever pressurizing the machine.

Finding Leaks and the Water-Side Danger

Leak location Detection method Why it matters
Shaft seals (open-drive) Electronic detector, bubble solution Classic infiltration point on older machines
Flanges / access plates / gaskets Electronic detector, bubble solution Large sealing surfaces on the shells

Tube sheets / water boxes Pressurize refrigerant side, inspect water side for bubbles Tube/water-box failure lets water into the refrigerant

Rupture-disc housing Visual + electronic detector A weeping disc admits air on the vacuum side
Purge exhaust trend Monitor purge frequency High purge rate = active air leak
Why Tube Failures Are So Serious

Unlike a high-pressure system that leaks refrigerant out, a low-pressure system in a vacuum pulls cooling water IN through a failed tube or water-box gasket . That water reacts with refrigerant and heat to form acid, copper plating, and sludge , which can destroy compressor bearings. Detection tools include an acid test of the oil , a moisture test of the refrigerant , and eddy-current testing , in which an electromagnetic probe is run through each tube to find thinning or cracks so failing tubes can be plugged.

Example: A technician needs to pinpoint a slow leak on an R-123 chiller. They first raise the machine's pressure with its built-in heating/pressurization device, then sweep an electronic detector across the shaft seal and access flanges. The detector alarms at a flange gasket. Throughout, the technician keeps the pressure within the manufacturer's limit, well below the rupture-disc rating — pushing past it would blow the disc and vent the charge.

For the Exam: Raise a low-pressure system's pressure for a leak test with CONTROLLED HOT WATER or a BUILT-IN HEATING/PRESSURIZATION DEVICE first, then DRY NITROGEN (with a trace of refrigerant for electronic detection), always below the manufacturer's rupture-disc rating. A standing-vacuum test that rises then levels off = moisture; a continuous rise = an air leak. Tube/water-box failures pull water INTO the refrigerant under vacuum, forming acid and copper plating.