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BLD-HVAC07-07 · Lesson 8 · 16 clock hours · lab

Refrigerant Recovery, Recycling, and Recharge Procedures

Objective. Students will perform a complete refrigerant recovery from a training system to the required level, evacuate the system to the trade-accepted vacuum level, and recharge by weight using a refrigerant scale, in full compliance with EPA Section 608.

Why These Procedures Matter

Refrigerants are regulated under Section 608 of the Clean Air Act. It is illegal to knowingly vent refrigerants into the atmosphere during service, maintenance, or disposal of refrigeration equipment. As a certified technician, you are personally responsible for compliance every time you open a refrigerant circuit. Violations carry serious civil penalties. EPA 608 Universal certification is your legal authorization to purchase and handle refrigerants — and this lab puts those rules into direct practice.

Safety First

Before touching any fitting, put on your PPE: safety glasses and chemical-resistant gloves are the minimum for refrigerant work. Refrigerants and refrigerant oil mist can cause frostbite on skin and serious eye injury on contact. Never work on a pressurized system with loose fittings. Verify that the recovery cylinder is rated for the refrigerant you are recovering, is not overfilled (recovery cylinders must never exceed 80% of capacity by liquid weight), and shows no visible damage or corrosion. If you smell refrigerant in an enclosed space, ventilate immediately — some refrigerants displace oxygen and can cause asphyxiation, and certain decomposition products are acutely toxic. Apply lockout/tagout (LOTO) to the equipment's electrical disconnect before any work that takes you inside the cabinet.

Step 1 — Refrigerant Recovery

Recovery means removing refrigerant from a system and storing it in an approved recovery cylinder without releasing it to the atmosphere. EPA regulations set required recovery levels based on equipment type and system capacity. Your training rig falls into the commercial refrigeration category; know the required recovery level for that equipment class before you begin.

Setup sequence:

1. Attach manifold gauges to the high- and low-side service ports.

2. Connect the manifold center hose to the inlet of the certified recovery machine.

3. Connect the recovery machine outlet hose to the recovery cylinder inlet valve.

4. Purge hoses of air according to the manufacturer's procedure.

5. Open service valves in the correct sequence — low-side first for vapor recovery, then high-side — to prevent liquid slugging in the compressor.

6. Weigh the recovery cylinder on the digital scale and record the starting weight (tare weight plus any existing refrigerant).

7. Start the recovery machine and monitor suction pressure; continue until the required recovery level is reached.

8. Close service valves, close cylinder valve, stop the machine, and weigh the cylinder again. The weight gain equals the mass of refrigerant recovered.

Always use color-coded, properly labeled cylinders. Gray cylinder with yellow top is the standard color scheme for mixed/unknown refrigerants. Single-refrigerant cylinders have specific colors — know your refrigerant's assigned color.

Step 2 — Triple Evacuation (Dehydration)

After recovery, moisture and non-condensables remain in the system. A two-stage vacuum pump removes them. The triple evacuation method is a reliable field procedure:

1. Connect the two-stage vacuum pump and micron gauge to the manifold.

2. Pull the first vacuum to the trade-accepted level (typically 500 microns or below, confirmed on the micron gauge — check your equipment specifications).

3. Break the vacuum with dry nitrogen to approximately atmospheric pressure. Dry nitrogen absorbs residual moisture.

4. Pull the second vacuum to the same target level.

5. Break vacuum with dry nitrogen again.

6. Pull the third (final) vacuum. Confirm the system holds at the target level for a minimum standing time (often 10 minutes with pump isolated) — a rising micron reading indicates a leak or remaining moisture.

Record micron gauge readings at the end of each evacuation stage on your service record. A micron gauge is required — manifold gauges are not accurate enough to confirm deep vacuum. Change vacuum pump oil when it appears dark or milky; contaminated oil dramatically reduces pump performance.

Step 3 — Refrigerant Recharge by Weight

Charging by weight is the most accurate method for a sealed system and is required when the nameplate specifies a charge weight. Never charge by "feel" or pressure alone.

1. Place the refrigerant supply cylinder on the digital scale and tare (zero) the scale with the cylinder in place, hoses connected, and valves closed.

2. Record the nameplate-specified charge weight from the unit data plate.

3. With the system still under vacuum, open the liquid-line service valve and the cylinder valve; allow liquid refrigerant to enter the high side.

4. Monitor the scale reading. When the target weight has been dispensed, close the cylinder valve immediately.

5. Start the system and allow pressures and temperatures to stabilize (allow several minutes of runtime).

6. Measure suction-line superheat and liquid-line subcooling with your manifold gauges and temperature clamps. Compare readings to manufacturer specifications. Minor adjustment may be needed.

7. Record pre-charge and post-charge pressures, final charge weight, superheat, and subcooling on the EPA-style service record. The service record must be retained as required by regulation.

Completing the Service Record

EPA Section 608 requires that technicians maintain records of refrigerant added and removed from equipment above the regulatory threshold. Your service record must include: date of service, technician name and certification number, refrigerant type, amount recovered, amount added, and equipment identification. Incomplete records are a compliance failure — in this lab, an incomplete form means the lab is not passed.

Key terms8

RecoveryRemoving refrigerant from a system and storing it in an approved cylinder without releasing it to the atmosphere; required by EPA Section 608 before opening a refrigerant circuit.
RecyclingCleaning recovered refrigerant by oil separation and single or multiple passes through filter-driers for reuse on-site; differs from reclamation, which restores refrigerant to ARI-700 purity standards at a certified facility.
Recovery cylinderA DOT-approved pressure vessel specifically designed and labeled for storing recovered refrigerant; must not be filled beyond 80% of capacity by liquid weight.
Micron gauge (electronic vacuum gauge)An instrument that measures vacuum in microns of mercury (µmHg); required for confirming that a system has reached the deep vacuum necessary for proper dehydration before recharging.
Triple evacuationA dehydration method in which the system is evacuated, broken with dry nitrogen, and re-evacuated three times to progressively remove moisture and non-condensables.
SuperheatThe number of degrees that refrigerant vapor temperature exceeds the saturation (boiling) temperature at the same pressure; measured at the suction line to verify proper evaporator performance and protect the compressor.
SubcoolingThe number of degrees that liquid refrigerant temperature is below the saturation (condensing) temperature at the same pressure; measured at the liquid line to confirm a solid column of liquid entering the metering device.
Charge by weightIntroducing a precisely measured mass of refrigerant — read on a calibrated digital scale — equal to the nameplate-specified charge; the most accurate recharge method for sealed systems.

Worked examples4

1. The recovery cylinder weighed 12.40 lb before recovery and 17.65 lb after recovery. The training rig nameplate states the original charge is 5.20 lb. Did recovery meet the ±0.2 lb check?
  1. Calculate mass recovered: 17.65 lb − 12.40 lb = 5.25 lb recovered.
  2. Calculate the difference from the nameplate charge: 5.25 lb − 5.20 lb = +0.05 lb difference.
  3. Compare to the allowed tolerance: 0.05 lb is less than 0.2 lb, so the result is within tolerance.
Answer: 5.25 lb was recovered, which is 0.05 lb above the nameplate charge — within the ±0.2 lb tolerance. The recovery check passes.
2. The nameplate specifies a charge of 3.50 lb (56.0 oz). After recharge, the scale shows 3.47 lb (55.5 oz) was added. Is this within the ±0.5 oz lab acceptance criterion?
  1. Convert nameplate charge to ounces: 3.50 lb × 16 oz/lb = 56.0 oz.
  2. Convert actual charge to ounces: 3.47 lb × 16 oz/lb = 55.52 oz.
  3. Calculate difference: 56.0 oz − 55.52 oz = 0.48 oz short.
  4. Compare to tolerance: 0.48 oz is less than 0.5 oz, so the charge is within specification.
Answer: The actual charge of 55.52 oz is 0.48 oz below the target of 56.0 oz — within the ±0.5 oz criterion. The recharge check passes.
3. The suction-line temperature is measured at 28 °F and the saturation temperature at suction pressure is 14 °F. What is the superheat, and does it fall within a typical target range of 8–12 °F for this training rig?
  1. Calculate superheat: 28 °F − 14 °F = 14 °F of superheat.
  2. Compare to specification range: 14 °F is above the 8–12 °F target range.
Answer: Superheat is 14 °F, which is above the specified 8–12 °F range. The system may be slightly undercharged or have another issue; investigate before accepting the recharge.
4. During final evacuation, the micron gauge reads 480 microns with the pump running. The pump is isolated (valves closed) and after 10 minutes the gauge reads 510 microns. What does this indicate, and should recharge proceed?
  1. Note the standing vacuum test result: the system rose from 480 to 510 microns over 10 minutes — a 30-micron rise.
  2. Evaluate the rise: a slow, small rise can indicate residual moisture outgassing and may be acceptable if it stabilizes; a continuous rapid rise above 1,000 microns strongly indicates a leak.
  3. In this case 510 microns is still below a common 500-micron hold target ceiling — however, technicians should confirm the reading stabilizes and does not continue climbing before proceeding.
  4. If readings continue to rise past the target, do not recharge; find and repair the leak or continue evacuation.
Answer: A rise to 510 microns requires monitoring. If the reading stabilizes at or below the target level, recharge may proceed. If it continues to climb, a leak or significant moisture is present and must be addressed first.
In class: Pre-recovery setup: students connect recovery machine per manufacturer instructions, don appropriate PPE (safety glasses, chemical-resistant gloves), open service valves in correct sequence, and recover refrigerant from a training rig to a recovery cylinder; they weigh the cylinder before and after to confirm the amount recovered. · Triple evacuation and deep vacuum: students connect a two-stage vacuum pump and micron gauge, evacuate the system, break vacuum with dry nitrogen, re-evacuate twice more, and record micron readings at each stage until the system holds at the trade-accepted level. · Refrigerant recharge by weight: using a digital refrigerant scale, students charge the system with the nameplate-specified charge weight, record pre- and post-charge pressures, verify superheat and subcooling against specifications, and complete an EPA-style service record.
Materials: Training refrigeration rigs, certified refrigerant recovery machine, recovery cylinders (color-coded, labeled), two-stage vacuum pump, micron gauge, digital refrigerant scale, manifold gauge sets, safety glasses, chemical-resistant gloves, EPA Section 608 service record forms, NCCER HVAC Trainee Guide Level 3
Check: Instructor checks: recovery cylinder weight gain matches expected charge (±0.2 lb), vacuum held at trade-accepted level before recharge, final charge weight within ±0.5 oz of nameplate, service record fully completed. All four criteria must be met to pass. Aligns with EPA 608 Universal exam content area.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

EPA 608 — Environmental Regulations and Recovery Requirements
1. Under EPA Section 608, what is the primary reason refrigerant must be recovered before opening a refrigerant circuit?
EPA 608 — Safe Handling of Refrigerants and Recovery Cylinders
2. A recovery cylinder must never be filled beyond what percentage of its capacity by liquid weight?
NATE — System Service and Diagnostics
3. Why is a micron gauge required when verifying deep vacuum, rather than relying on manifold gauges alone?
NCCER HVAC — System Evacuation and Dehydration
4. During a triple evacuation, what is the purpose of breaking vacuum with dry nitrogen between each evacuation stage?
NATE — System Diagnostics and Charging
5. A technician charges a system by weight and the scale shows the correct amount has been added, but the suction-line superheat reading is significantly higher than the manufacturer's specification. What is the most likely next action?
EPA 608 — Technician Safety
6. Which PPE items are the minimum required when connecting hoses to recover refrigerant from a pressurized system?
EPA 608 — Recordkeeping and Regulatory Compliance
7. What information is required on an EPA-compliant refrigerant service record?
HVAC Excellence — System Evacuation and Quality Verification
8. A system is isolated from the vacuum pump at 420 microns and the micron gauge reading climbs steadily to 2,400 microns over five minutes. What does this most likely indicate?
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