10.7 - Type III Memorization Sheet

Module: Universal Review and Mock Examinations
Purpose: One-page-target rapid review of the highest-priority Type III facts before Universal mock examinations
Covers: Type III material consolidated from Sections 9.1–9.10
Regulatory and safety verification basis: Current Module 9 material verified August 13, 2026
Use: Memorize the low-pressure fundamentals, purge-unit logic, leak-test limits, recovery sequence, freeze prevention, oil-service values, vapor-first charging, evacuation requirement, and safety distinctions below; return to Module 9 when a condition or exception is unclear

1. Type III = Low-Pressure Appliances

Type III certification applies to covered:

LOW-PRESSURE APPLIANCES

Current Section 608 classification:

LIQUID-PHASE SATURATION PRESSURE
<45 psia at 104°F
→ LOW PRESSURE
→ TYPE III

Common Type III Examples

Low-pressure centrifugal chillers.
Low-pressure absorption chillers.
Other appliances that satisfy the current low-pressure refrigerant classification.

Exam Traps

LARGE CHILLER
≠
AUTOMATICALLY TYPE III

LOW SIDE
≠
LOW-PRESSURE APPLIANCE

CHILLER
≠
AUTOMATICALLY TYPE III

Pressure classification controls.

2. Why Type III Is Different

Many low-pressure chillers operate with refrigerant-side pressure:

BELOW ATMOSPHERIC PRESSURE

Therefore:

AIR + MOISTURE
→ CAN LEAK INTO THE APPLIANCE

instead of refrigerant always leaking outward.

Consequences of Air and Moisture Infiltration

Noncondensables accumulate.
Head pressure can increase.
Purge-unit operation can increase.
Moisture can contaminate refrigerant and lubricant.
Corrosion and acid formation can become concerns.
Water entering the refrigerant side creates major freeze-risk problems during deep recovery.

Important Distinction

LOW-PRESSURE APPLIANCE
≠
EVERY POINT ALWAYS UNDER VACUUM

Some conditions, shutdown states, or service procedures can place parts of the appliance at positive gauge pressure.

3. Major Type III Components

Know the function of:

Evaporator.
Condenser.
Centrifugal compressor.
Purge unit.
Rupture disc / pressure-relief protection.
Water boxes.
Evaporator charging valve.
Oil system, when the chiller uses one.
Refrigerant monitor.

Fast Component Logic

EVAPORATOR
→ chilled-water heat exchanger
→ low refrigerant-side region
→ charging connection used in Type III exam procedure

CONDENSER
→ rejects heat
→ condenses refrigerant vapor

PURGE UNIT
→ removes noncondensables
→ minimizes refrigerant loss

RUPTURE DISC
→ non-reclosing emergency pressure relief

4. Purge Units

Because air can enter a low-pressure chiller:

NONCONDENSABLES
→ COLLECT
→ MUST BE REMOVED

Purge-Unit Purpose

PURGE UNIT
→ REMOVE AIR / NONCONDENSABLES
→ MINIMIZE REFRIGERANT LOSS

A purge unit is not the recovery machine used to recover the entire chiller charge.

Frequent Purging

FREQUENT PURGE OPERATION
→ POSSIBLE AIR INFILTRATION / LEAK

It is a diagnostic clue, not proof of the exact leak location.

Purge and Head Pressure

Noncondensables can:

RAISE CONDENSER / HEAD PRESSURE

and reduce system efficiency.

Moisture Clue

Excess moisture collected or indicated by the purge system can suggest:

POSSIBLE WATER-SIDE / TUBE LEAKAGE

Further diagnosis is required.

Exam Trap

PURGE UNIT
≠
LICENSE TO VENT REFRIGERANT

Refrigerant in purge discharge must be controlled according to the applicable system design and refrigerant-management requirements.

5. Low-Pressure Leak Detection and Pressurization

Preferred General Concept

Because the appliance may normally be under vacuum:

RAISE PRESSURE CAREFULLY
→ THEN LEAK CHECK

Controlled methods taught in Module 9 include:

Warm water.
Heater blankets or other controlled warming where permitted.
Dry nitrogen where the approved procedure permits it.

Type III Exam-Preparation Maximum

10 psig
→ LOW-PRESSURE CHILLER LEAK-TEST MAXIMUM

Treat this as the Type III examination-preparation maximum used in this course.

It is not a target pressure that must always be reached.

Pressure-Control Rule

CONTROLLED PRESSURIZATION
→ DO NOT EXCEED SAFE / SPECIFIED LIMIT

Open-Drive Shaft Seal

For an open-drive low-pressure machine:

SHAFT SEAL
→ IMPORTANT LEAK-CHECK LOCATION

Tube-Leak Concern

A tube leak can allow:

WATER
→ ENTER REFRIGERANT CIRCUIT

This becomes especially dangerous during recovery because decreasing refrigerant pressure lowers saturation temperature and can freeze water.

6. Recovery Sequence

High-priority Type III recovery sequence:

REMOVE ACCESSIBLE BULK LIQUID FIRST
→ RECOVER REMAINING VAPOR
→ CONTINUE TO REQUIRED ENDPOINT
→ ISOLATE / WAIT / CHECK PRESSURE REBOUND

Why Liquid First?

LIQUID
→ contains much more refrigerant mass per unit volume
→ faster bulk refrigerant removal

Vapor Still Matters

After liquid removal:

A LARGE VAPOR MASS MAY REMAIN

Therefore:

NO VISIBLE LIQUID
≠
RECOVERY COMPLETE

Recovery-Machine Condenser

During vapor recovery:

RECOVERY-MACHINE CONDENSER
→ rejects heat
→ helps condense recovered refrigerant

Adequate cooling is essential.

Traditional Recovery-Equipment Values

10 psig
→ LOW-PRESSURE RECOVERY-UNIT
HIGH-PRESSURE CUTOUT

15 psig
→ LOW-PRESSURE RECOVERY-VESSEL
RUPTURE-DISC EXAM VALUE

These values refer to different components.

Exam Trap

15 psig recovery-vessel rupture disc
≠
universal chiller relief-device rating

7. Freeze Prevention During Recovery

As chiller pressure falls:

REFRIGERANT SATURATION TEMPERATURE FALLS

If water remains in the heat-exchanger tubes:

DEEP RECOVERY
→ LOW REFRIGERANT TEMPERATURE
→ WATER CAN FREEZE
→ TUBE DAMAGE POSSIBLE

Normal Water Management

During normal recovery when the system is configured for circulation:

CHILLED-WATER CIRCULATION
+
CONDENSER-WATER CIRCULATION / MANAGEMENT
→ REDUCE FREEZE RISK

The traditional Type III recovery relationship taught in Module 9 is:

CHILLER WATER PUMPS
+
RECOVERY COMPRESSOR
+
RECOVERY-CONDENSER COOLING WATER
→ OPERATE AS REQUIRED

Suspected Tube Leak

If tube leakage is suspected under the Type III exam procedure:

DRAIN EVAPORATOR WATER SIDE
+
DRAIN CONDENSER WATER SIDE
BEFORE RECOVERY

This reduces the chance that water will be pulled into the low-pressure refrigerant circuit and freeze.

Charging Freeze Trap

LIQUID REFRIGERANT
+
DEEP VACUUM
→ RAPID FLASHING
→ STRONG COOLING
→ WATER-FREEZING RISK

Therefore:

DO NOT BEGIN DEEP-VACUUM RECHARGE
WITH BULK LIQUID

8. Refrigerant in Oil

Traditional oil-lubricated low-pressure chillers can retain refrigerant dissolved in compressor oil.

As pressure falls:

REFRIGERANT
→ COMES OUT OF SOLUTION
→ ADDITIONAL VAPOR LOAD

Therefore:

APPARENT RECOVERY ENDPOINT
→ PRESSURE MAY REBOUND

Oil-Heating Exam Value

130°F
→ TYPE III OIL-HEATING EXAM VALUE
BEFORE OIL REMOVAL

The purpose is to help drive dissolved refrigerant out of the oil before removal.

Current Oil-Change Pressure Provision

NO HIGHER THAN 5 psig
→ CURRENT SPECIAL OIL-CHANGE OPENING PROVISION

Do Not Confuse

130°F
→ OIL TEMPERATURE

5 psig
→ OIL-CHANGE PRESSURE LIMIT

25 mm Hg absolute
→ NORMAL TYPE III FINAL RECOVERY ENDPOINT

They are three different concepts.

Modern Equipment Reminder

Not every modern centrifugal chiller uses a conventional oil system.

The traditional oil-service procedure remains important because it is part of Type III examination preparation.

9. Recharging Low-Pressure Systems

Charging Connection

Type III exam emphasis:

EVAPORATOR CHARGING VALVE
→ MANUFACTURER-DESIGNATED LOW REFRIGERANT-SIDE
CHARGING CONNECTION

The phrase lowest access point does not mean:

ANY FITTING PHYSICALLY CLOSEST TO THE FLOOR

Use the designated refrigerant charging connection.

Vapor First

When a low-pressure chiller is deeply evacuated:

INTRODUCE VAPOR FIRST

Why?

VAPOR ADDED
→ PRESSURE RISES
→ SATURATION TEMPERATURE RISES
→ FREEZE RISK DECREASES

Then:

WHEN SAFE UNDER THE APPROVED PROCEDURE
→ TRANSITION TO LIQUID CHARGING

Critical Memory Rule

DEEP VACUUM
→ VAPOR FIRST
→ LIQUID LATER

Blend Distinction

If a refrigerant blend must leave its source container as liquid to prevent fractionation, that does not cancel the Type III vapor-first requirement.

The technician can:

REMOVE BLEND FROM SOURCE AS LIQUID
→ CONTROL / VAPORIZE IT AS REQUIRED
→ INTRODUCE VAPOR FIRST INTO DEEPLY EVACUATED CHILLER

Exam Trap

BLEND CHARGED FROM SOURCE AS LIQUID
≠
BULK LIQUID DIRECTLY INTO DEEP VACUUM

10. Type III Evacuation Requirement

Current Table 1 requirement for a low-pressure appliance:

25 mm Hg absolute

Important Features

The Type III value is:

The same for recovery equipment manufactured before November 15, 1993.
The same for recovery equipment manufactured on or after November 15, 1993.
Not changed by a 200-lb charge boundary.

Unit Trap

25 mm Hg absolute
≠
25 in. Hg vacuum

For absolute-pressure scales:

SMALLER NUMBER
→ DEEPER VACUUM

Pressure-Rebound Check

After reaching the required recovery vacuum:

ISOLATE
→ WAIT A FEW MINUTES
→ OBSERVE PRESSURE

A pressure rise can indicate:

Residual liquid refrigerant evaporating.
Refrigerant coming out of oil.
Moisture / outgassing during post-service vacuum evaluation.
Leakage.

For Type III recovery exam questions, residual refrigerant and refrigerant in oil are especially important clues.

Qualifying Non-Major Opening

When all current conditions are satisfied:

LOW-PRESSURE APPLIANCE
→ MAY BE PRESSURIZED TO
NO HIGHER THAN 0 psig
BEFORE OPENING

Leak Prevents Normal Endpoint

If a leak prevents reaching the prescribed evacuation level without substantial contamination:

ISOLATE WHERE POSSIBLE

Then:

NON-LEAKING PORTION
→ NORMAL REQUIRED LEVEL

LEAKING PORTION TO BE OPENED
→ LOWEST ATTAINABLE LEVEL
→ NOT ABOVE 0 psig

11. Type III Safety and Machinery Rooms

Rupture Disc

RUPTURE DISC
→ EMERGENCY PRESSURE RELIEF
→ NON-RECLOSING

After rupture, it must be replaced appropriately.

Relief-Valve Arrangement

For Type III exam preparation:

DO NOT SIMPLY INSTALL
TWO ORDINARY INDEPENDENT RELIEF VALVES IN SERIES
AS A SUBSTITUTE FOR A PROPER RELIEF SYSTEM

Approved engineered arrangements can differ; follow equipment design, applicable code, and manufacturer requirements.

Refrigerant Monitor Versus Oxygen Monitor

REFRIGERANT MONITOR
→ measures refrigerant concentration

OXYGEN MONITOR
→ measures oxygen concentration

One does not automatically replace the other.

Oxygen Deficiency

OSHA general-industry terminology:

OXYGEN <19.5%
→ OXYGEN-DEFICIENT ATMOSPHERE

Machinery Room Versus Confined Space

MACHINERY ROOM
≠
AUTOMATICALLY OSHA CONFINED SPACE

Individual spaces such as:

Pits.
Vessels.
Water boxes.
Other enclosures.

must be evaluated by their actual configuration and hazards.

Water-Side Hazards

Before opening water-side equipment:

STOP / ISOLATE HAZARDOUS ENERGY
→ VERIFY PRESSURE IS RELIEVED
→ CONTROL UNEXPECTED PUMP STARTUP

A stopped pump does not prove:

WATER-SIDE PRESSURE = 0

Static head or trapped pressure may remain.

Code Review

NEWEST PUBLISHED STANDARD
≠
AUTOMATICALLY ENFORCEABLE IN EVERY JURISDICTION

Follow:

Locally adopted code.
Authority having jurisdiction (AHJ).
Manufacturer instructions.
Employer safety procedures.

12. Type III Numbers to Know Cold

Number / Value	Type III Meaning
<45 psia at 104°F	Current low-pressure appliance classification
10 psig	Type III leak-test maximum used in exam preparation
10 psig	Traditional low-pressure recovery-unit high-pressure cutout
15 psig	Traditional low-pressure recovery-vessel rupture-disc exam value
130°F	Type III oil-heating exam value
5 psig	Current special oil-change opening pressure limit
25 mm Hg absolute	Current normal Type III Table 1 evacuation endpoint
0 psig	Current qualifying non-major opening / leaking-section ceiling when applicable
19.5% oxygen	OSHA oxygen-deficient threshold used in the Module 9 safety discussion

The Type III Number Separation

10 psig
→ LEAK-TEST EXAM MAXIMUM

10 psig
→ RECOVERY-UNIT CUTOUT

15 psig
→ RECOVERY-VESSEL RUPTURE DISC

130°F
→ OIL HEATING

5 psig
→ OIL-CHANGE OPENING

25 mm Hg ABSOLUTE
→ FINAL NORMAL RECOVERY ENDPOINT

13. Highest-Priority Type III Exam Traps

Trap 1

Low pressure
→ refrigerant always leaks outward

Wrong. Air and moisture can leak inward when the appliance is below atmospheric pressure.

Trap 2

Purge unit
→ recovery machine for entire chiller

Wrong.

Trap 3

Frequent purging
→ normal proof that no leak exists

Wrong. Frequent purging can indicate air infiltration.

Trap 4

Remove vapor first

Wrong when accessible bulk liquid is available.

Type III recovery:

LIQUID FIRST
→ VAPOR SECOND

Trap 5

No liquid visible
→ recovery complete

Wrong. A substantial vapor mass and refrigerant in oil may remain.

Trap 6

Stop all water flow during deep recovery

Wrong for the normal recovery arrangement. Water must be circulated or otherwise managed to prevent freezing.

Trap 7

Suspected tube leak
→ continue normal water circulation without evaluation

Wrong. Under the Type III exam procedure, drain the evaporator and condenser water sides before recovery.

Trap 8

Deep vacuum
→ add bulk liquid first

Wrong.

VAPOR FIRST
→ LIQUID LATER

Trap 9

25 mm Hg absolute
→ 25 in. Hg vacuum

Wrong.

Trap 10

15 psig
→ universal chiller rupture-disc rating

Wrong. The 15-psig exam value belongs to the low-pressure recovery vessel.

Trap 11

Refrigerant monitor
→ oxygen monitor

Wrong. They measure different quantities.

Trap 12

Machinery room
→ automatically confined space

Wrong.

Trap 13

Water pump stopped
→ water pressure is zero

Wrong.

14. Type III Final Memory Map

TYPE III
→ LOW PRESSURE
→ <45 psia @ 104°F

BELOW ATMOSPHERE
→ AIR + MOISTURE IN

PURGE UNIT
→ REMOVE NONCONDENSABLES
→ FREQUENT PURGING MAY SIGNAL INFILTRATION

LEAK TEST
→ CONTROLLED PRESSURIZATION
→ 10 psig EXAM MAXIMUM

RECOVERY
→ LIQUID FIRST
→ VAPOR SECOND
→ CONDENSER COOLING
→ WATER MANAGEMENT

RECOVERY UNIT CUTOUT
→ 10 psig

RECOVERY-VESSEL RUPTURE DISC
→ 15 psig

FREEZE PREVENTION
→ CIRCULATE / REMOVE WATER AS REQUIRED

SUSPECTED TUBE LEAK
→ DRAIN EVAPORATOR + CONDENSER WATER SIDES

OIL
→ REFRIGERANT CAN REMAIN DISSOLVED
→ 130°F EXAM VALUE
→ OIL CHANGE ≤5 psig

RECHARGE FROM DEEP VACUUM
→ EVAPORATOR CHARGING VALVE
→ VAPOR FIRST
→ LIQUID LATER

NORMAL TYPE III ENDPOINT
→ 25 mm Hg ABSOLUTE

QUALIFYING NON-MAJOR OPENING
→ ≤0 psig

SAFETY
→ PRESSURE RELIEF
→ REFRIGERANT MONITORING
→ VENTILATION
→ WATER-SIDE ENERGY CONTROL

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