Light Commercial Refrigeration: Walk-ins, Reach-ins and Ice Machines
Walk-ins, reach-ins and ice machines
This domain applies refrigeration fundamentals to equipment you can touch: walk-in coolers and freezers, reach-in cases, prep tables and ice machines. Know the differences. A walk-in freezer needs electric or hot-gas defrost with defrost termination and fan delay; a cooler may use off-cycle defrost; reach-ins often have a condensate evaporator pan; ice machines run a freeze cycle then a harvest cycle initiated by a pressure or thermistor control, using hot gas to release the slab.
Know the service points: unit cooler fan motors and blade clearance, door gaskets and frame heaters, drain lines with traps, defrost timers and their fail-safe position, temperature versus pressure controls, and condenser cleanliness. On ice machines, water quality, inlet screens, curtain/bin switches and head pressure controls matter more than charge.
Traps: overcharging a critically charged reach-in, replacing a thermostat when the defrost timer is stuck in defrost, ignoring a plugged drain trap that floods the box, and diagnosing an ice machine as failed when it is simply in harvest.
Worked example: a walk-in cooler sitting at 40°F with a heavily iced evaporator and timer pins pushed in likely has a defrost termination or timer failure, not a refrigerant shortage. Defrost the coil, confirm termination at roughly 50-60°F coil temperature, and verify the timer advances out of defrost.