9.11 - Quick Reference

Module: Type III Low-Pressure Appliances
Covers: Sections 9.1–9.10
Regulatory and safety verification date: August 13, 2026
Use: Rapid review before the Module 9 Type III practice questions and later Universal certification review

1. Type III Scope and Low-Pressure Fundamentals

Type III certification applies to covered:

LOW-PRESSURE APPLIANCES

The current Section 608 low-pressure definition is based on refrigerant liquid-phase saturation pressure:

BELOW 45 psia AT 104°F
→ LOW-PRESSURE APPLIANCE
→ TYPE III

Representative low-pressure refrigerants introduced in this module include:

• R-11.
• R-113.
• R-123.
• R-245fa.

Important Boundaries

LOW-PRESSURE APPLIANCE
≠
every chiller

CENTRIFUGAL COMPRESSOR
≠
automatically Type III

LOW-PRESSURE APPLIANCE
≠
every point in the refrigeration circuit is always under vacuum

Type III classification depends on the refrigerant pressure category, not on:

• Chiller size.
• Compressor appearance.
• Building type.
• Whether the appliance is located in a machinery room.

2. Pressure Direction and Leak Direction

A low-pressure chiller can operate below atmospheric pressure.

When:

Pinside < Patmosphere

the likely leak direction is:

AIR + MOISTURE
→ INTO THE CHILLER

When:

Pinside > Patmosphere

the possible leak direction is:

REFRIGERANT
→ OUT OF THE CHILLER

Exam Trap

Do not assume:

SHUTDOWN
→ entire chiller automatically positive

Leak direction depends on the local pressure difference at the leak location.

3. Low-Pressure Chiller Component Map

High-Priority State Reminder

EVAPORATOR
→ refrigerant boils

COMPRESSOR
→ vapor in
→ higher-pressure vapor out

CONDENSER
→ refrigerant condenses

Water-Side Reminder

Water and refrigerant are normally separated by the heat-exchanger tube wall.

A tube failure can create:

WATER SIDE
↔
REFRIGERANT SIDE

4. Air, Moisture, Noncondensables, and Purge Units

Why Air Enters

CHILLER PRESSURE BELOW ATMOSPHERE
+
LEAK
→
AIR + MOISTURE ENTER

Air that enters becomes a source of:

NONCONDENSABLES

Where Noncondensables Collect

For the traditional Type III exam model:

NONCONDENSABLES
→ collect near the upper / top condenser region

Purge-Unit Purpose

PURGE UNIT
→ removes noncondensables
→ minimizes refrigerant loss

A purge stream can contain:

REFRIGERANT VAPOR
+
AIR / NONCONDENSABLES

The purge unit separates them so that refrigerant is retained or returned while noncondensables are removed.

Diagnostic Clues

FREQUENT / EXCESSIVE PURGING
→ POSSIBLE AIR LEAK

NONCONDENSABLES
→ POSSIBLE HIGHER CONDENSER / HEAD PRESSURE

EXCESSIVE MOISTURE IN PURGE
→ POSSIBLE TUBE LEAK

Important Caution

HIGH HEAD PRESSURE
≠
automatic proof of noncondensables

Other heat-rejection problems can also raise condenser pressure.

PURGE UNIT
→ removes noncondensables
≠
repairs the leak

5. Low-Pressure Leak Detection and Pressurization

Low-pressure operation can draw air inward, so an outward refrigerant leak can be difficult to locate while the chiller is under vacuum.

For leak checking, the Type III sequence taught in this module is:

APPROVED HEAT / HOT WATER FIRST
→
REGULATED NITROGEN SECOND where permitted

Heat-based methods can include:

• Controlled hot water.
• Approved built-in pressurization/heating equipment.
• Approved heater blankets where applicable.

Leak-Test Pressure

For this module’s Type III exam preparation:

LOW-PRESSURE CHILLER LEAK-TEST MAXIMUM
→ 10 psig

10 psig is a:

MAXIMUM

not a required target for every leak test.

Never Use

OXYGEN

or:

COMPRESSED AIR

for refrigerant-system pressure testing.

Important Distinction

LEAK TEST
→ up to the applicable test limit

is different from:

QUALIFYING NON-MAJOR OPENING
→ no higher than 0 psig

The two procedures must not be mixed.

6. High-Priority Type III Leak Locations and Methods

Leak Direction Reminder

UNDER VACUUM
→ air may leak IN

POSITIVE PRESSURE
→ refrigerant may leak OUT

7. Type III Recovery Sequence

The core recovery sequence is:

1. RECOVER BULK LIQUID FIRST
↓
2. RECOVER REMAINING VAPOR
↓
3. CONTINUE TO REQUIRED ENDPOINT
↓
4. WAIT / CHECK FOR PRESSURE REBOUND

Why Liquid First?

LIQUID
→ much greater mass per unit volume
→ faster bulk refrigerant removal

Why Vapor Recovery Is Still Required

NO BULK LIQUID
≠
NO REFRIGERANT

A large low-pressure chiller can still contain a substantial vapor mass after liquid recovery.

Classic Exam Example

350-ton R-11 chiller
at 0 psig
→ about 100 lb of vapor can still remain
after bulk liquid is removed

This is a representative exam example, not a universal engineering value for every chiller.

8. Recovery-Machine Relationships

During the classic normal Type III recovery condition:

CHILLER SYSTEM WATER PUMPS
→ ON

RECOVERY COMPRESSOR
→ ON

RECOVERY CONDENSER COOLING WATER
→ ON

Vapor-Recovery Path

CHILLER VAPOR
→ RECOVERY COMPRESSOR
→ RECOVERY-MACHINE CONDENSER
→ RECOVERY VESSEL

Recovery Condenser

The recovery-machine condenser rejects heat from compressed refrigerant.

For the traditional water-cooled Type III recovery arrangement:

COOLING WATER FLOW ↓
→ HEAT REJECTION ↓
→ RECOVERY DISCHARGE PRESSURE ↑
→ HIGH-PRESSURE CUTOUT MAY TRIP

9. Traditional Type III Recovery-Equipment Values

Keep the component and value together.

Do Not Confuse the Two 10-psig Values

10 psig
→ leak-test maximum

and:

10 psig
→ recovery-unit high-pressure cutout

are associated with different procedures.

Do Not Transfer 15 psig to the Chiller

15 psig
→ traditional LOW-PRESSURE RECOVERY-VESSEL rupture-disc value

It is not a universal centrifugal-chiller rupture-disc rating.

Actual chiller pressure-relief ratings are equipment-specific.

10. Freeze Prevention During Recovery

As refrigerant pressure falls:

PRESSURE ↓
→ SATURATION TEMPERATURE ↓
→ REMAINING REFRIGERANT BOILS AT LOWER TEMPERATURE
→ HEAT IS ABSORBED
→ FREEZE RISK ↑

Current Type III Principle

DURING REFRIGERANT EVACUATION
→ CIRCULATE OR REMOVE WATER
→ PREVENT FREEZING

Normal Water-Tight Chiller

When water circulation is the approved procedure:

MOVING WATER
→ brings heat to cold tube surfaces
→ reduces local freeze risk

Important Caution

PUMP MOTOR ON
≠
proof of adequate water flow

Verify actual flow according to the equipment procedure.

11. Suspected Tube Leak: Special Water-Side Rule

A suspected tube leak changes the normal water-management approach.

If the refrigerant side is under vacuum and the water side remains pressurized:

PWATER > PREFRIGERANT
→ WATER CAN ENTER THROUGH FAILED TUBE

For the Type III exam-preparation condition:

SUSPECTED TUBE LEAK
→ DRAIN EVAPORATOR WATER SIDE
→ DRAIN CONDENSER WATER SIDE
→ THEN RECOVER ACCORDING TO APPROVED PROCEDURE

Do Not Apply Blindly

NORMAL RECOVERY
→ circulate or remove water as required

SUSPECTED TUBE LEAK
→ do not blindly keep circulating water

12. Refrigerant Dissolved in Oil

Refrigerant can remain:

DISSOLVED IN COMPRESSOR OIL

even after bulk liquid and much of the free vapor have been recovered.

Oil Heating

Current Type III exam knowledge:

HEAT OIL TO 130°F
BEFORE REMOVING IT
TO MINIMIZE REFRIGERANT RELEASE

Heating helps:

REFRIGERANT LEAVE OIL
→ ENTER VAPOR SPACE
→ BECOME AVAILABLE FOR RECOVERY

Oil Foaming

SUDDEN PRESSURE DROP
→ dissolved refrigerant rapidly leaves oil
→ OIL FOAMING

Controlled temperature and pressure changes are important.

Field Rule

130°F
→ important Type III exam value

but:

ACTUAL OIL-HEATING PROCEDURE
→ manufacturer limits and approved service procedure

Some modern centrifugal chillers are oil-free; identify the actual machine design.

13. Current Oil-Change Pressure Rule

For an oil change, current § 82.156 permits the appliance or isolated portion to be:

EVACUATED OR PRESSURIZED
TO NO HIGHER THAN 5 psig
BEFORE OPENING

or the permitted system-receiver procedure may be used.

Keep the Values Separate

130°F
→ oil-heating exam value

5 psig MAX
→ oil-change opening / receiver pressure condition

25 mm Hg absolute
→ normal Type III Table 1 evacuation requirement

OIL REMOVED
≠
RECOVERY COMPLETE

14. Recharging Low-Pressure Systems

Correct Charging Connection

Current Type III exam relationship:

CENTRIFUGAL CHILLER
→ EVAPORATOR CHARGING VALVE

The outline’s lowest access point should be interpreted as the designated low evaporator refrigerant-side charging connection.

Do not use:

ANY PHYSICALLY LOW FITTING

unless it is actually the manufacturer-designated charging connection.

Initial Charge

DEEPLY EVACUATED LOW-PRESSURE CHILLER
→ VAPOR FIRST
→ LIQUID LATER

15. Why Vapor Is Charged First

If bulk liquid refrigerant enters a deep vacuum:

LIQUID
→ RAPID FLASH EVAPORATION
→ LATENT HEAT ABSORBED
→ STRONG LOCAL COOLING
→ WATER IN TUBES CAN FREEZE

Initial vapor charging instead causes:

VAPOR ADDED
→ PRESSURE ↑
→ SATURATION TEMPERATURE ↑
→ FREEZE RISK ↓

Vapor-to-Liquid Transition

VAPOR FIRST
↓
raise pressure and saturation temperature
↓
establish safe condition
↓
CONTROLLED LIQUID CHARGING

There is no universal project-wide transition pressure.

Use the manufacturer-approved procedure.

16. Type III Required Evacuation Level

The current normal Section 608 Table 1 requirement for a low-pressure appliance is:

25 mm Hg ABSOLUTE

Both Recovery-Equipment Date Columns

Recovery/recycling equipment
BEFORE Nov. 15, 1993
→ 25 mm Hg absolute

Recovery/recycling equipment
ON / AFTER Nov. 15, 1993
→ 25 mm Hg absolute

Critical Date Trap

The November 15, 1993 date applies to:

RECOVERY / RECYCLING EQUIPMENT

not the:

CHILLER MANUFACTURE DATE

17. Type III Charge-Size Trap

For the normal low-pressure Table 1 row:

< 200 lb
→ 25 mm Hg absolute

≥ 200 lb
→ 25 mm Hg absolute

The 200-lb boundary changes some Type II evacuation rows, but it does not change the normal Type III low-pressure endpoint.

18. Understand the Unit: mm Hg Absolute

The current Type III requirement is:

25 mm Hg ABSOLUTE

not:

25 in. Hg VACUUM

Absolute-Pressure Reminder

0 mm Hg absolute
→ perfect vacuum

25 mm Hg absolute
→ current Type III normal Table 1 endpoint

~760 mm Hg absolute
→ standard atmosphere

Do not replace the regulatory value with a different unit unless a conversion is clearly identified as approximate.

19. Pressure-Rebound Check

After reaching the required recovery vacuum:

REACH ENDPOINT
↓
STOP / ISOLATE AS DIRECTED
↓
WAIT A FEW MINUTES
↓
OBSERVE PRESSURE

If Pressure Rises

Primary Type III refrigerant clues:

REMAINING LIQUID REFRIGERANT

or:

REFRIGERANT LEAVING OIL

During broader post-service vacuum diagnosis, also consider:

• Moisture.
• Outgassing.
• Appliance leakage.
• Hose / service-setup leakage.

Exam Trap

PRESSURE RISE
≠
automatic proof of an external leak

and:

ONE MOMENTARY READING
AT 25 mm Hg absolute
≠
automatic proof recovery is complete

20. Major Repair

Current major maintenance, service, or repair includes removal of:

• Compressor.
• Condenser.
• Evaporator.
• Auxiliary heat-exchange coil.

It also includes work that:

UNCOVERS AN OPENING
> 4 in² OF FLOW AREA
FOR > 15 min

Memory Rule

MAJOR REPAIR
→ named major component removal
OR
→ >4 in² opening exposed >15 min

For a normal non-leaking low-pressure appliance undergoing major repair:

TABLE 1
→ 25 mm Hg absolute

unless another specific regulatory exception applies.

21. Qualifying Non-Major Opening

A limited current exception applies only when the regulatory conditions are satisfied.

For a qualifying low-pressure non-major opening:

PRESSURIZE
TO NO HIGHER THAN 0 psig
BEFORE OPENING

Important

NON-MAJOR
≠
automatically 0 psig

The complete § 82.156 conditions must be satisfied.

The permitted pressurization method also depends on refrigerant boiling-point conditions.

Do not interpret nitrogen as universally permitted for every qualifying non-major opening.

22. Leaking Appliance: Lowest Attainable Level

If a leak prevents the normal Table 1 level from being reached, or if deeper evacuation would substantially contaminate recovered refrigerant:

ISOLATE LEAKING
FROM NON-LEAKING COMPONENTS
WHEREVER POSSIBLE

Then:

NON-LEAKING PORTION
→ 25 mm Hg absolute

and:

LEAKING PORTION
→ LOWEST ATTAINABLE
without substantially contaminating recovered refrigerant
→ NOT ABOVE 0 psig

Important

LEAK EXISTS
≠
recovery no longer required

A good-faith recovery effort still applies.

23. Type III Pressure / Temperature / Safety Numbers

Keep every number tied to its procedure.

Highest-Risk Number Confusion

10 psig
→ leak-test maximum
OR
→ recovery-unit cutout
depending on context

15 psig
→ recovery-vessel rupture disc
NOT universal chiller relief rating

5 psig
→ oil-change provision
NOT Type III final evacuation

0 psig
→ qualifying non-major / leaking-component exception boundary
NOT normal Type III Table 1 endpoint

25 mm Hg absolute
→ normal Type III Table 1 endpoint

24. Rupture Disc and Pressure-Relief Safety

Rupture Disc

RUPTURE DISC
→ EMERGENCY OVERPRESSURE PROTECTION
→ NON-RECLOSING

After rupture:

DISC MUST BE REPLACED
according to approved procedure

Do not:

• Use a rupture disc as a normal pressure regulator.
• Block or cap a required relief path.
• Substitute an arbitrary rating.
• Intentionally operate the device during a leak test.

Pressure-Relief Valve

PRESSURE-RELIEF VALVE
→ opens to relieve abnormal pressure

Many designs can reclose after pressure falls.

Required relief protection must remain effective.

25. Relief-Valve Arrangement Trap

Do not simply install two ordinary independent pressure-relief valves in series:

VESSEL
→ RELIEF VALVE 1
→ RELIEF VALVE 2
→ DISCHARGE

The downstream valve can restrict or interfere with the upstream relief path.

Do Not Overgeneralize

Approved engineered arrangements can include:

• Dual/changeover relief valves.
• Rupture-disc / pressure-relief-valve combinations.

Therefore:

TWO ORDINARY RELIEF VALVES
IN SIMPLE SERIES
→ NOT PROPER REDUNDANCY

but:

APPROVED ENGINEERED RELIEF COMBINATION
→ follow code / listing / manufacturer design

26. Machinery-Room Refrigerant Detection and Ventilation

Refrigerant Monitor

REFRIGERANT MONITOR
→ measures refrigerant in room air

It is not:

CHILLER PRESSURE SENSOR

Oxygen Monitor

OXYGEN MONITOR
→ measures oxygen concentration

The two instruments answer different questions.

Alarm / Ventilation Relationship

REFRIGERANT DETECTED
→ ALARM / VENTILATION RESPONSE
→ PERSONNEL FOLLOW EMERGENCY PROCEDURE

Important Caution

VENTILATION FAN ON
≠
AUTOMATICALLY SAFE TO ENTER

Atmospheric conditions must be evaluated according to the applicable procedure.

27. Toxicity, Oxygen Deficiency, and Confined Spaces

High-priority OSHA value:

O₂ < 19.5% BY VOLUME
→ OXYGEN-DEFICIENT ATMOSPHERE

Do Not Confuse

LOW-PRESSURE REFRIGERANT
≠
LOW-TOXICITY REFRIGERANT

Machinery Room

MACHINERY ROOM
≠
automatically an OSHA confined space

Evaluate the actual space against the confined-space criteria.

Possible Type III service locations that may require evaluation include:

• Pits.
• Vaults.
• Vessels.
• Certain water boxes.
• Below-grade enclosures.

A hazardous atmosphere can exist even where the space does not meet the confined-space definition.

28. Water-Side Safety

Stored Pressure

PUMP OFF
≠
ZERO WATER PRESSURE

Possible pressure sources include:

• Static head.
• Trapped pressure.
• Expansion tanks.
• Building pressure.
• Pump discharge.
• Thermal expansion.

Water-Box Service Sequence

ISOLATE
↓
CONTROL APPLICABLE HAZARDOUS ENERGY
↓
RELIEVE STORED PRESSURE
↓
DRAIN / VENT AS REQUIRED
↓
VERIFY SAFE CONDITION
↓
OPEN

Do not loosen water-box cover bolts to use the cover as a pressure-relief device.

Heavy Covers

Large water-box covers can require:

• Rated hoist.
• Lifting fixture.
• Rigging.
• Mechanical support.
• Manufacturer lifting points.

Plan the lift before the final bolts are removed.

29. Current Machinery-Room Code Review

For exam preparation, know the Type III machinery-room safety concepts.

For actual design or service compliance, check:

CURRENT PUBLISHED SAFETY STANDARD
+
LOCALLY ADOPTED CODE
+
AUTHORITY HAVING JURISDICTION (AHJ)
+
EQUIPMENT LISTING
+
MANUFACTURER INSTRUCTIONS
+
EMPLOYER SAFETY PROCEDURE

The module’s current-code review identifies:

ANSI/ASHRAE Standard 15-2024

and:

ANSI/ASHRAE Standard 34-2024

as the current published ASHRAE editions.

Important

CURRENT PUBLISHED EDITION
≠
automatically the legally adopted edition everywhere

Local adoption and amendments control enforceability.

30. Highest-Priority Type III Distinctions

31. Type III Rapid Service Decision Sequence

Use this as an exam-reasoning sequence.

Step 1 — Confirm Type III Scope

LOW-PRESSURE APPLIANCE?
→ <45 psia saturation pressure at 104°F

Step 2 — Identify the Service Condition

Is the task primarily:

• Leak detection?
• Recovery?
• Tube-leak work?
• Oil service?
• Recharging?
• Evacuation?
• Safety / machinery-room response?

Step 3 — Control Water-Side Condition

NORMAL RECOVERY
→ circulate or remove water as approved

SUSPECTED TUBE LEAK
→ drain water sides before recovery

Step 4 — Recover

LIQUID FIRST
→ VAPOR SECOND

Step 5 — Manage Oil Refrigerant

HEAT OIL AS REQUIRED
→ 130°F exam value
→ recover released refrigerant

Step 6 — Reach the Applicable Evacuation Condition

Normal low-pressure Table 1:

25 mm Hg absolute

Qualifying exceptions must be identified separately.

Step 7 — Wait and Observe

WAIT A FEW MINUTES
→ PRESSURE REBOUND?

If yes, determine whether:

• Refrigerant remains.
• Refrigerant is leaving oil.
• Moisture/outgassing is present.
• A leak exists.

Step 8 — Recharge

EVAPORATOR CHARGING VALVE
→ VAPOR FIRST
→ LIQUID LATER when approved

Step 9 — Restore Safety Systems

Confirm the applicable:

• Relief protection.
• Refrigerant monitoring.
• Ventilation.
• Water-side condition.
• Manufacturer controls.

32. Twenty Type III Facts to Know Before the Practice Tests

1. Type III applies to low-pressure appliances.
2. Current low-pressure classification is below 45 psia saturation pressure at 104°F.
3. Below atmospheric pressure, a leak can draw air and moisture in.
4. Air in the chiller becomes noncondensables.
5. The purge unit’s primary purpose is to remove noncondensables while minimizing refrigerant loss.
6. Frequent purging can indicate an air leak.
7. Excessive purge moisture can indicate a tube leak.
8. Type III leak checking uses approved heat first, then regulated nitrogen where permitted.
9. The Type III low-pressure chiller leak-test maximum used in this course is 10 psig.
10. Recover liquid first, then recover vapor.
11. A large chiller can still contain substantial refrigerant vapor after all visible liquid is gone.
12. During normal recovery, water must be circulated or removed to prevent freezing.
13. If tube leakage is suspected, the Type III exam procedure calls for draining evaporator and condenser water sides before recovery.
14. Oil should be heated to 130°F before removal for the current Type III exam topic.
15. The oil-change opening / receiver pressure condition is no higher than 5 psig.
16. Recharge through the evaporator charging valve.
17. In deep vacuum, charge vapor before liquid.
18. The current normal Type III evacuation requirement is 25 mm Hg absolute.
19. After reaching the required recovery vacuum, wait a few minutes and watch for pressure rise.
20. A machinery-room refrigerant monitor detects refrigerant in room air, while an oxygen monitor measures oxygen.

33. Essential Module 9 Figures

Use the existing Module 9 figures for rapid visual review:

1. Figure 9.1.1 - Low-Pressure Centrifugal Chiller
   Review Type III centrifugal-chiller layout and inward/outward leak-direction concept.

2. Figure 9.2.1 - Low-Pressure Chiller Components
   Review evaporator, condenser, compressor, water boxes, purge unit, relief protection, charging valve, oil system, and room monitor.

3. Figure 9.3.1 - Low-Pressure Purge Unit Process
   Review air/moisture infiltration, noncondensable collection, purge separation, and diagnostic clues.

4. Figure 9.4.1 - Low-Pressure Leak Test Setup
   Review controlled pressurization and Type III leak-test relationships.

5. Figure 9.5.1 - Type III Recovery Sequence
   Review liquid-first recovery, vapor recovery, recovery-machine condenser, water management, and recovery-equipment protection values.

6. Figure 9.9.1 is planned in Section 9.9 as the visual review of the current 25 mm Hg absolute evacuation requirement and principal Type III exceptions.

No New Quick-Reference Figure

No Figure 9.11.x is added because the governing Module 9 outline does not specify a quick-reference figure.

34. Final Type III Memory Sheet

TYPE III
→ LOW-PRESSURE APPLIANCES

LOW PRESSURE
→ <45 psia saturation pressure at 104°F

Pinside < Patmosphere
→ AIR + MOISTURE IN

PURGE UNIT
→ REMOVE NONCONDENSABLES
→ MINIMIZE REFRIGERANT LOSS

FREQUENT PURGING
→ POSSIBLE AIR LEAK

EXCESSIVE PURGE MOISTURE
→ POSSIBLE TUBE LEAK

LEAK TEST
→ APPROVED HEAT FIRST
→ NITROGEN SECOND where permitted
→ MAX 10 psig

RECOVERY
→ LIQUID FIRST
→ VAPOR SECOND

NORMAL RECOVERY
→ CIRCULATE OR REMOVE WATER
→ PREVENT FREEZING

SUSPECTED TUBE LEAK
→ DRAIN EVAPORATOR + CONDENSER WATER SIDES

RECOVERY-UNIT CUTOUT
→ 10 psig

RECOVERY-VESSEL RUPTURE DISC
→ 15 psig

OIL
→ HEAT TO 130°F BEFORE REMOVAL

OIL CHANGE
→ NO HIGHER THAN 5 psig

CHARGING CONNECTION
→ EVAPORATOR CHARGING VALVE

DEEPLY EVACUATED CHILLER
→ VAPOR FIRST
→ LIQUID LATER

TYPE III TABLE 1
→ 25 mm Hg ABSOLUTE

BEFORE / AFTER NOV. 15, 1993 RECOVERY EQUIPMENT
→ SAME 25 mm Hg ABSOLUTE

<200 lb / ≥200 lb
→ SAME 25 mm Hg ABSOLUTE

QUALIFYING NON-MAJOR
→ NO HIGHER THAN 0 psig BEFORE OPENING

LEAKING PORTION
→ LOWEST ATTAINABLE
→ ≤0 psig

ENDPOINT REACHED
→ WAIT A FEW MINUTES
→ WATCH FOR PRESSURE REBOUND

RUPTURE DISC
→ EMERGENCY PROTECTION
→ NON-RECLOSING

TWO ORDINARY RELIEF VALVES
→ DO NOT SIMPLY INSTALL IN SERIES

REFRIGERANT MONITOR
→ REFRIGERANT IN ROOM AIR

OXYGEN MONITOR
→ OXYGEN CONCENTRATION

O₂ <19.5%
→ OXYGEN-DEFICIENT ATMOSPHERE

MACHINERY ROOM
≠ AUTOMATICALLY A CONFINED SPACE

PUMP OFF
≠ ZERO WATER PRESSURE

References

Current Regulatory and EPA Sources

1. Electronic Code of Federal Regulations, 40 CFR § 82.152 - Definitions, current low-pressure appliance definition and major-maintenance/service/repair definition. Verified August 13, 2026.

2. Electronic Code of Federal Regulations, 40 CFR § 82.156 - Proper Evacuation of Refrigerant From Appliances, current low-pressure Table 1 requirement, non-major opening provision, leaking-appliance exception, oil-change provision, and service-practice requirements. Verified August 13, 2026.

3. Electronic Code of Federal Regulations, 40 CFR § 82.161 - Technician Certification, current Type III certification scope. Verified August 13, 2026.

4. U.S. Environmental Protection Agency, Section 608 Test Topics, current Type III examination-topic framework for purge units, leak detection, recovery, freeze prevention, oil heating, recharging, evacuation, and machinery-room safety. Verified August 13, 2026.

5. U.S. Environmental Protection Agency, Stationary Refrigeration Service Practice Requirements, current service-practice summary. Verified August 13, 2026.

6. U.S. Environmental Protection Agency, Required Level of Evacuation of Appliances, current low-pressure evacuation table. Verified August 13, 2026.

Current Safety Sources

7. Occupational Safety and Health Administration, 29 CFR 1910.146 - Permit-Required Confined Spaces, confined-space definitions and oxygen-deficient-atmosphere threshold. Verified August 13, 2026.

8. Occupational Safety and Health Administration, 29 CFR 1910.147 - The Control of Hazardous Energy, hazardous-energy control requirements for applicable servicing. Verified August 13, 2026.

9. ASHRAE, current published ANSI/ASHRAE Standard 15-2024 and ANSI/ASHRAE Standard 34-2024 information used for the machinery-room current-code review in Section 9.10. Verified August 13, 2026.

Module 9 Cross-References

10. Section 9.1 - Low-Pressure Appliance Fundamentals.

11. Section 9.2 - Low-Pressure Chiller Components.

12. Section 9.3 - Air Moisture and Purge Units.

13. Section 9.4 - Low-Pressure Leak Detection and Pressurization.

14. Section 9.5 - Type III Recovery Sequence.

15. Section 9.6 - Freeze Prevention During Recovery.

16. Section 9.7 - Refrigerant in Oil.

17. Section 9.8 - Recharging Low-Pressure Systems.

18. Section 9.9 - Type III Evacuation Requirements.

19. Section 9.10 - Type III Safety and Machinery Rooms.

20. Section 9.12 - Practice Questions Set 1.