Introduction to Walk-In Freezers : Operation of Walk-in Freezers

 1. Overview of the Refrigeration Cycle:

• The evaporator is inside the cooling zone and absorbs heat as refrigerant vaporizes.
• The condenser is outside the cooling zone and rejects heat as refrigerant condenses.
• The system has a high-pressure side (condenser) and a low-pressure side (evaporator).

2. Installation Guidelines for Piping:

• Check manufacturer guidelines for specific installation instructions.
• Primary concerns:
  • Minimize pressure drop.
  • Prevent oil from lying in the suction line and ensure it returns to the compressor.
  • Avoid suction line picking up ambient heat or causing water damage due to sweating.

3. Piping Sizing:

• Use a piping chart for sizing suction and liquid lines based on refrigerant type, BTU/hour capacity, and temperature application.
• Determine equivalent length of pipe:
  • Length of pipe plus 3 feet per fitting or
  • Length of pipe multiplied by 1.5 (more precise method).
• Suction lines should slope downward toward refrigerant flow at 1/8 inch per foot.

4. Traps and Risers:

• Place traps in the suction line at the evaporator.
• Trap the suction line every 20 feet of vertical riser when the compressor is above the evaporator.
• Install an inverted P trap at the top of a vertical suction riser for proper refrigerant circulation.

5. Insulation and Placement:

• Insulate low-temperature suction lines with 1-inch pipe insulation.
• Ensure enough space between evaporator and walls; avoid placing above doors or in storage/retrieval interference areas.

6. Condensing Unit Installation:

• Ensure adequate ventilation if installed indoors.
• If outdoors, include means to keep high-side pressure above minimum value during cold weather (e.g., fan cycling control or head pressure control valve).
• Use pump down method and crankcase heater to prevent refrigerant migration during the off cycle.
• Cover outdoor units for environmental protection.

7. Drain Piping Guidelines:

• Slope drain line 1/4 inch per foot to remove condensate during defrost cycles.
• Use copper piping, not PVC.
• Insulate drain line and install self-regulating heat tape inside the walk-in space.
• Install a P trap outside the box to prevent warm air from entering.