HVAC School - For Techs, By Techs Introduction to Walk-in Refrigeration
In this podcast episode, refrigeration tech Eric Mele talks us through some common characteristics of walk-in freezers and refrigerators. Eric recently discussed reach-in refrigerators on the podcast, and you can listen to him talk about those HERE.
Common walk-in applications include coolers, freezers, and wine rooms. You may even see some package units. Condensers typically go on top of the box or the roof, and evaporators are inside the refrigerators. Many of these refrigerators also have pump down solenoids on their equipment. Thermostats mostly control the opening or closing of the solenoid valve. To cycle the unit, you shut off the liquid line and let the system pump all the refrigerant into the condenser.
Evaporators tend to come in the side-discharge or pancake-style varieties. Wine rooms may also have ducted evaporators. Some older evaporators may not have fans; we call these gravity evaporators.
Heaters are components that you'll see quite often on walk-in equipment. Drain pan and drain line heaters are critical for walk-in coolers, especially freezers. You can test them by touch or by using a thermal imaging camera. Freezers also have door heaters. Walk-ins also have low-ambient controls. Fan cycling is a low-ambient strategy, but commercial walk-in refrigerators may also have a headmaster.
When you first start working on walk-ins, you may feel overwhelmed if you don't have all the parts on you. However, if a unit has multiple fans and only one is not working, you can typically still run the equipment if you cover the faulty fan and seal up the opening in the shroud. The goal is to get (or keep) the equipment running to save consumable products.
Eric and Bryan also discuss:
- Pressure switches
- Defrost controls
- Troubleshooting equipment (sight glasses, etc.)
- Adjusting charge
- Superheat values
- Patching coils