EPA 608 Technician Certification Refrigeration Cycle, Gauges, and the Three Rs Summary

Part A is the compressor. Following the arrows, the hot high-pressure vapor goes next to part B, the condenser, where it gives off heat and becomes a liquid. Then comes the metering device (C) and the evaporator (D).

Wrong choices

• Accumulator: An accumulator would be in the suction line before the compressor, and it is not shown.
• Metering device: The metering device is the small part where pressure drops (part C).
• Evaporator: The evaporator is where low-pressure refrigerant absorbs heat; it comes after the metering device (part D).

In the evaporator, low-pressure liquid refrigerant boils into vapor and absorbs heat from the air or water around it. That heat is later given off in the condenser.

Wrong choices

• Receiver: The receiver stores liquid refrigerant.
• Condenser: The condenser gives off heat to the outside.
• Compressor: The compressor raises the pressure of the vapor; it does not cool the space.

To recover is to remove refrigerant in any condition from an appliance and store it in an external container, without necessarily testing or processing it.

Wrong choices

• Clean it with filter-driers for reuse by the same owner: Cleaning for reuse is recycling.
• Release it slowly to the air: Releasing refrigerant is venting, which is illegal.
• Clean it to meet the new-refrigerant purity standard: Meeting the purity standard is reclaiming.

The condenser removes heat and turns the high-pressure vapor into a high-pressure liquid. That liquid flows through the liquid line to the metering device, which is Point 2.

Wrong choices

• Point 3: Point 3 is after the metering device, where the refrigerant is a low-pressure mix of liquid and vapor.
• Point 4: Point 4 is the suction line from the evaporator, where the refrigerant is a low-pressure vapor.
• Point 1: Point 1 is between the compressor and condenser, where the refrigerant is a high-pressure vapor.

To recycle is to remove refrigerant and clean it for reuse in equipment of the same owner, usually with oil separation and filter-driers that reduce moisture, acid, and particles. It does not meet all reclamation requirements.

Wrong choices

• Send it to be destroyed: Destruction is a separate process.
• Reprocess it to AHRI 700 specifications and verify it by testing: Reprocessing to full specifications with lab testing is reclaiming.
• Remove it and store it without any processing: Removing and storing is recovering.

To reclaim is to reprocess refrigerant to all the purity specifications in Appendix A (based on AHRI Standard 700) and verify them with the required analysis. Only certified reclaimers may do this.

Wrong choices

• Clean it with a filter-drier in the field: Field cleaning is recycling.
• Remove it from the system into a recovery cylinder: Removing it into a cylinder is recovering.
• Return it to the same system after a repair: Returning it to the same system does not require reclaiming.

On a standard manifold, the blue hose and compound gauge connect to the low side, the red hose and gauge connect to the high side, and the yellow center hose goes to the recovery machine, vacuum pump, or refrigerant cylinder.

Wrong choices

• Hose C (red): The red hose goes with the high-side gauge and connects to the system's high side.
• Hose A (blue): The blue hose goes with the low-side gauge and connects to the system's low side.
• None of them; the center port stays capped: The center port is not left capped; it is the connection used for recovery, evacuation, and charging.

The compressor draws in low-pressure vapor and compresses it into a high-pressure, high-temperature vapor, which then goes to the condenser.

Wrong choices

• Removes moisture from the refrigerant: A filter-drier removes moisture.
• Lowers the pressure of the liquid before the evaporator: The metering device lowers the pressure.
• Turns liquid into vapor to absorb heat: Boiling liquid into vapor happens in the evaporator.

By common practice, the low-side (compound) gauge and hose are blue, the high-side gauge and hose are red, and the center hose is yellow.

Wrong choices

• Red: Red is for the high side.
• Green: Green is not the standard low-side color.
• Yellow: Yellow is for the center (utility) hose.

Mixed refrigerants usually cannot be separated or reclaimed, so they may have to be destroyed at high cost. Use a separate, labeled recovery cylinder for each refrigerant.

Wrong choices

• Mixing makes the cylinder lighter and harder to weigh: Mixing does not make the cylinder lighter in any useful way.
• Mixed refrigerant can be sold as a new blend: Mixed refrigerant cannot legally be sold as a new blend.
• Mixing is fine as long as both are HFCs: Mixing two HFCs still creates a contaminated mixture.