What is the typical sequence of steps in a gas defrost cycle?

The typical sequence of steps in a gas defrost cycle is designed to effectively remove ice build-up from evaporator coils while minimizing disruption to the refrigeration system. The correct choice outlines this sequence clearly, starting with the system in refrigeration mode, which maintains temperatures within the desired range before initiating the defrost process.

After transitioning into the pump-down phase, the refrigerant is cleared from the evaporator to eliminate liquid refrigerant and enhance heat transfer during the defrost. This step is crucial as it helps prepare the system for effective defrosting by ensuring that the coils are not overly congested with refrigerant. Next, the system undergoes a soft start to gradually increase the flow of hot gas used for defrosting, as abrupt changes can put strain on the equipment.

Once proper conditions are established, the gas defrost occurs, where hot refrigerant is circulated through the coils to melt the accumulated frost. Following this, the system enters a soft stop phase, allowing for a smooth transition back to normal operation. Finally, the re-freeze phase restores normal refrigeration operation, allowing the coils to return to the appropriate cooling temperature.

This sequence is not only efficient in removing frost but also prevents damage to the system components by managing pressure changes and fluid dynamics