EPA 608 Type 2 Study Guide: High-Pressure Systems

EPA 608 Type 2 certification authorizes you to service high-pressure refrigeration and air conditioning systems, covering the vast majority of residential and commercial HVAC equipment. This guide provides complete coverage of Type 2 exam topics including system classifications, recovery requirements for various refrigerants, leak repair thresholds, evacuation procedures, charging methods, and industry best practices for high-pressure system service.

What Are Type 2 High-Pressure Systems?

Type 2 encompasses appliances using high-pressure refrigerants (boiling point below 50°F at atmospheric pressure) except for small appliances under 5 pounds and motor vehicle air conditioning. High-pressure refrigerants operate above atmospheric pressure in both the evaporator and condenser at normal operating temperatures.

Common Type 2 equipment:

• Residential Air Conditioning: Split systems, package units, heat pumps for single-family homes
• Light Commercial AC: Rooftop units (RTUs), split systems for small businesses and offices
• Commercial Refrigeration: Walk-in coolers and freezers, reach-in refrigerators, display cases
• Ice Machines: Commercial ice makers (over 5 lbs refrigerant charge)
• Heat Pumps: Air-source heat pumps, mini-splits, ductless systems
• Process Cooling: Industrial process chillers using high-pressure refrigerants
• Condensing Units: Remote condensers for refrigeration applications

What Type 2 Does NOT Cover

Understanding Type 2 boundaries prevents certification confusion:

• Small Appliances: Equipment with 5 lbs or less refrigerant (requires Type 1)
• Low-Pressure Chillers: Centrifugal chillers using R-123 or similar (requires Type 3)
• Motor Vehicle AC: Cars, trucks, buses (requires separate MVAC-like certification)
• Specialty Applications: Marine refrigeration, aircraft AC, railway car AC (industry-specific certifications)

Type 2 Recovery Requirements

Recovery Levels by Refrigerant Type

EPA mandates specific vacuum levels based on refrigerant classification and recovery equipment capability. Type 2 recovery requirements are more stringent than Type 1 due to larger refrigerant charges and environmental impact.

Refrigerant Class	Examples	Required Vacuum
HCFC-22 Systems	R-22 residential and commercial AC	10 inches Hg vacuum
Other HCFCs/CFCs	R-12, R-502 (legacy systems)	10 inches Hg vacuum
HFC Systems	R-134a, R-404A, R-407C	0 psig
Very High-Pressure	R-410A (residential AC)	0 psig
HFO Blends	R-454B, R-32 (newer systems)	0 psig

Recovery Procedures

Vapor Recovery (Push-Pull Method): Most common for Type 2 systems. Connect recovery machine to both high and low sides, operate in push-pull mode pulling vapor from low side while pushing recovered liquid back through high side. Fastest method for systems with significant refrigerant charges.

Liquid Recovery: For systems with liquid line service valves, recover liquid refrigerant first (much faster than vapor recovery), then switch to vapor recovery to clear remaining refrigerant. Always recover liquid into recovery cylinder vapor port to prevent overfilling.

Passive Recovery: After active recovery reaches required vacuum, close manifold valves and monitor system pressure. If pressure rises (indicating remaining liquid refrigerant), continue recovery. Wait 5-10 minutes between recovery cycles on large systems.

Special Recovery Considerations

Heat Pumps: Some heat pumps have reversing valve positions affecting recovery efficiency. Position reversing valve to cooling mode during recovery for best results. Check service manual for manufacturer recommendations.

Refrigerant Blends: R-410A, R-404A, R-407C are zeotropic or near-azeotropic blends. Never top off blends with vapor — always charge as liquid to prevent composition shift. Recover blends as liquid when possible to maintain proper composition for recycling.

Contaminated Refrigerant: If you suspect refrigerant contamination (wrong refrigerant added, air, moisture), recover into separate cylinder marked "contaminated" and send for reclamation. Don't mix contaminated refrigerant with clean refrigerant.

Common Type 2 Refrigerants

Current Refrigerants in Use

R-22 (HCFC-22): Legacy refrigerant being phased out. Production banned January 1, 2020, but existing equipment can use reclaimed or recycled R-22 indefinitely. Most common refrigerant in older residential AC and commercial refrigeration. Being replaced by R-410A (residential) and R-404A/R-407C (commercial).

R-410A (Puron): Industry standard for new residential and light commercial AC since 2010. Near-azeotropic blend of R-32 and R-125. Operates at 60% higher pressure than R-22, requiring specific equipment design. Cannot be used as R-22 drop-in replacement.

R-404A: Common in commercial refrigeration (walk-in coolers, ice machines, display cases). Blend of R-125, R-143a, and R-134a. High GWP (3,922) driving phase-down under AIM Act. Being replaced by R-448A, R-449A in new equipment.

R-407C: R-22 replacement for some commercial applications. Zeotropic blend exhibiting temperature glide during phase change. Must be charged as liquid to prevent composition shift. Moderate GWP compared to R-404A.

R-134a: Used in commercial refrigeration, chillers, and some automotive applications. Single-component HFC with lower GWP than blends. Common in ice machines and medium-temperature refrigeration.

New Lower-GWP Refrigerants

EPA regulations under the AIM Act are phasing down high-GWP refrigerants. Newer systems use lower-GWP alternatives:

• R-32: Single-component HFC replacing R-410A in residential AC. 68% lower GWP than R-410A. Mildly flammable (A2L classification) requiring updated installation practices.
• R-454B: R-410A replacement blend. 78% lower GWP. A2L flammable, increasingly common in 2024+ residential equipment.
• R-448A: R-404A replacement for commercial refrigeration. 65% lower GWP. Non-flammable, drop-in compatible with many R-404A systems.
• R-449A: Another R-404A alternative. 66% lower GWP. Better energy efficiency than R-404A in many applications.

Leak Repair Requirements

Federal Leak Repair Thresholds

EPA requires leak repairs when annual leak rates exceed specific thresholds. Leak rate is calculated as percentage of full charge lost over 12 months:

Commercial refrigeration:

• 35% annual leak rate threshold for systems with 50+ lbs refrigerant
• 20% for systems with comfort cooling applications
• Calculated annually: (refrigerant added - refrigerant recovered during service) / full charge

Industrial process refrigeration:

• 35% annual leak rate for systems with 50+ lbs refrigerant
• Some exemptions for process-critical equipment with documented repair plans

Repair timelines:

• Commercial equipment: 30 days from discovering leak exceeding threshold
• Industrial process: 30 days, with possible extension to 120 days if repairs require process shutdown
• Residential equipment: No federal leak repair requirements (follow state/local codes)

Leak Detection Methods

Electronic Leak Detectors: Standard tool for Type 2 systems. Heated-diode and infrared detectors locate leaks down to 0.1 oz/year. Test detector calibration weekly. Different refrigerants require different detector settings — verify your detector is set correctly before testing.

Ultrasonic Leak Detectors: Detect high-frequency sound of refrigerant escaping under pressure. Effective in noisy mechanical rooms where electronic detectors struggle. More expensive but useful for commercial applications.

Fluorescent Dye: Add UV-reactive dye to system, operate for 1-2 weeks, inspect with UV light. Excellent for finding intermittent leaks or leaks in inaccessible locations. Some refrigerants and compressor oils react poorly to dyes — check compatibility first.

Nitrogen Pressure Testing: After refrigerant recovery, pressurize system with dry nitrogen to operating pressure (not exceeding nameplate test pressure). Use soap bubbles or electronic detection to locate leaks. Most reliable method for finding small leaks before charging new refrigerant.

Bubble Testing: Mix dish soap with water, spray on suspected leak points, watch for bubbles. Simple, inexpensive, reliable for pressurized systems. Ineffective for very small leaks or vacuum-side leaks.

Evacuation and Dehydration

Why Evacuation Matters

Proper evacuation removes air, moisture, and non-condensables from refrigerant systems. Moisture causes acid formation damaging compressors, freeze-ups at expansion devices, and reduced system efficiency. Air increases head pressure, reduces capacity, and accelerates oil breakdown.

Deep vacuum requirements:

• 500 microns or lower for residential AC and heat pumps
• 500 microns for commercial refrigeration (250 microns preferred)
• Use electronic vacuum gauge (micron gauge), not compound gauge
• Hold vacuum for 15+ minutes — pressure should not rise more than 50 microns

Evacuation Procedure

1. Initial Pulldown: Connect vacuum pump to system high and low sides via manifold. Open both valves, start pump, evacuate to 500 microns or lower. Large systems may take 30-60+ minutes.
2. Vacuum Hold Test: Close manifold valves, shut off vacuum pump, monitor micron gauge for 15 minutes. Vacuum should remain stable below 500 microns.
3. If Vacuum Rises: Pressure rise indicates moisture or leak. If rise exceeds 100 microns in 15 minutes, continue evacuation or locate leak. Moisture removal requires extended evacuation or triple evacuation method.
4. Triple Evacuation: For severely contaminated systems, evacuate to 500 microns, break vacuum with dry nitrogen to 5 psig, evacuate again. Repeat 2-3 times. Most effective moisture removal method.
5. Final Check: Achieve and hold 500 microns for 15 minutes, then charge refrigerant per manufacturer specifications.

Charging Methods and Procedures

Vapor vs. Liquid Charging

Vapor Charging: Introduce refrigerant through low-side (suction) service port with system running. Use for single-component refrigerants (R-22, R-134a, R-32) and final topping after liquid charge. Cylinder remains upright, vapor port open. Slower than liquid charging but prevents compressor damage from liquid slugging.

Liquid Charging: Required for blends (R-410A, R-404A, R-407C) to prevent composition shift. Charge through high-side (liquid line) service port with system OFF, or through low side with metering device restricting flow. Invert cylinder or use liquid port. Never liquid charge into compressor suction while running — causes compressor damage.

Charging by Weight

Most accurate method. Place refrigerant cylinder on electronic scale, note starting weight, charge system until scale shows proper amount removed. Manufacturer nameplate or service manual specifies refrigerant charge weight.

Typical charges by system type:

• Residential split system 2-ton: 6-8 lbs R-410A
• Residential split system 3-ton: 9-12 lbs R-410A
• Commercial walk-in cooler: 15-40 lbs R-404A (varies by size)
• Commercial ice machine: 8-20 lbs R-404A or R-134a

Charging by Subcooling

Used when nameplate charge is unknown or system is field-charged (lineset length varies). Measure liquid line temperature and pressure, calculate subcooling (saturation temperature - actual temperature). Target subcooling typically 10-15°F for TXV systems.

Subcooling procedure:

1. System running in cooling mode, outdoor temp above 65°F
2. Measure liquid line pressure, convert to saturation temperature using PT chart
3. Measure liquid line temperature at service valve
4. Calculate: Subcooling = Saturation Temp - Actual Temp
5. Add refrigerant if subcooling low, recover refrigerant if subcooling high

Charging by Superheat

Used for fixed-orifice systems (piston, capillary tube). Measure suction line temperature and pressure, calculate superheat (actual temperature - saturation temperature). Target superheat varies by system design, typically 10-20°F.

Superheat procedure:

1. System running in cooling mode, load conditions stabilized
2. Measure suction pressure at service valve, convert to saturation temp
3. Measure suction line temperature 6-8 inches from compressor
4. Calculate: Superheat = Actual Temp - Saturation Temp
5. Add refrigerant if superheat high, recover refrigerant if superheat low

Type 2 System Components

Compressor Types

Reciprocating: Most common in residential AC and small commercial refrigeration. Piston-driven compression. Typical capacities 1-20 tons. Relatively inexpensive, serviceable, good efficiency.

Scroll: Industry standard for residential AC 2+ tons and commercial systems to 25 tons. Orbiting scroll compresses refrigerant in spiral chambers. Higher efficiency than reciprocating, quieter operation, fewer moving parts. Not field-serviceable — complete replacement when failed.

Rotary: Used in mini-splits, window AC units, small commercial applications. Single rotating vane or dual-vane design. Very quiet, compact, efficient at partial loads. Common in Japanese and European equipment.

Screw: Large commercial and industrial refrigeration (50-500+ tons). Twin helical screws compress refrigerant. Excellent efficiency, continuous compression, good part-load performance. High initial cost, complex controls.

Metering Devices

Thermostatic Expansion Valve (TXV): Automatically adjusts refrigerant flow based on superheat at evaporator outlet. Best efficiency across varying load conditions. Requires accurate charging (by subcooling). Common in commercial refrigeration and higher-efficiency AC.

Piston (Fixed Orifice): Fixed-size orifice restricts refrigerant flow. Simple, inexpensive, no moving parts. Less efficient at partial loads. Charge by superheat. Common in budget residential AC and older systems.

Electronic Expansion Valve (EEV): Computer-controlled valve optimizes refrigerant flow. Best efficiency and part-load performance. Expensive, requires sophisticated controls. Increasingly common in inverter-driven systems and commercial equipment.

Capillary Tube: Fixed-length tube provides refrigerant restriction. Critical charge — system must have exact refrigerant amount. Common in window AC units and small refrigeration. Not field-adjustable.

Safety Practices for Type 2 Work

High-Pressure System Hazards

Type 2 systems operate at significantly higher pressures than Type 1 equipment. R-410A systems reach 400+ psig high-side pressure in normal operation, creating serious injury risks from refrigerant release or system rupture.

Pressure safety:

• Never apply torch heat to pressurized systems — refrigerant decomposes at high temperature forming toxic gases
• Don't overpressurize during leak testing — follow nameplate test pressure (typically 300-600 psig depending on refrigerant)
• Use pressure-relief manifold gauges rated for refrigerant type (800 psig minimum for R-410A)
• Never cap off pressure relief valves or safety devices

Electrical Safety

Type 2 systems use 120V, 208V, 240V, or 480V power. Follow NFPA 70E electrical safety standards:

• Lockout/Tagout: De-energize equipment at disconnect, lock out power source, verify de-energized with voltmeter before touching electrical components
• Capacitor Discharge: Run capacitors can hold lethal charge for hours after power disconnection. Discharge with insulated tool before touching terminals
• Arc Flash: Use appropriate PPE when working on energized equipment. Maintain proper approach distances from exposed conductors

Refrigerant Handling Safety

• Ventilation: Work in well-ventilated areas. Refrigerant displaces oxygen causing asphyxiation in confined spaces
• Skin Contact: Liquid refrigerant causes instant frostbite. Wear safety glasses, gloves when connecting/disconnecting refrigerant lines
• Cylinder Safety: Secure cylinders upright, never exceed 80% fill, store away from heat sources, transport properly secured
• A2L Refrigerants: Eliminate ignition sources when working with R-32, R-454B. No smoking, no hot work, use spark-free tools

Type 2 Exam Study Tips

High-Frequency Exam Topics

Type 2 exams heavily test recovery requirements (know the vacuum levels for each refrigerant class), leak repair thresholds (35% for commercial refrigeration, 20% for comfort cooling), and proper charging methods (vapor vs. liquid charging, when to use each).

Memorize Recovery Levels

Create flashcards: R-22 = 10" Hg, R-410A = 0 psig, R-404A = 0 psig. Know why these differ (CFCs/HCFCs have higher ODP requiring deeper vacuum). Understand "0 psig" means gauge pressure, equivalent to 0 psig above atmospheric.

Understand Refrigerant Transitions

Questions about R-22 phaseout are common. Know production stopped 2020, existing systems can use reclaimed R-22, common replacements include R-410A (residential) and R-407C (commercial). HFC phasedown drives adoption of R-32, R-454B, R-448A.

Practice Calculations

Some exams include superheat/subcooling calculations. Practice: Given liquid line pressure 260 psig (R-410A), liquid line temp 100°F, what is subcooling? (Answer: Convert 260 psig to ~115°F saturation temp using PT chart, subcooling = 115 - 100 = 15°F)

Advancing Your Certification

Type 2 is the most versatile individual certification, covering the majority of residential and commercial HVAC work. However, Universal certification maximizes employment opportunities and eliminates equipment restrictions.

Next steps:

• Add Type 3: Study Type 3 Guide for low-pressure chiller certification (completes Universal)
• Universal Certification: Review Universal Guide for strategic approach to all exam sections
• Strengthen Core Knowledge: Revisit Core Guide for foundational regulations and science

Many HVAC employers prefer or require Universal certification. If you already have Type 2, adding Type 3 requires learning only low-pressure chiller material (centrifugal compressors, purge units, low-pressure refrigerants). Most Type 2 knowledge transfers directly to Type 3 work.