The Two Zone Evaporators

Owners used to other wine coolers often picture one cold source with a flap sharing it between the two zones. A Sub-Zero is built differently. In an island bar or family room off the heated part of the house that difference shows: the two zones rarely fail together, and the design tells us which side of the cabinet to open first.

One coil per zone

Sub-Zero’s product pages give each storage zone an evaporator of its own, dual evaporators in all, and credit them with keeping humidity steady and moderate. When one side warms and the other holds, the fault usually belongs to that side: its own coil, the air moving across it, or its sensor.

Frost on a single coil

A coil that has iced over is the evaporator problem we meet most, and the coil is rarely to blame. Water in the cabinet air collects on the coldest surface it can find. A door held slightly off its seal, or one opened again and again on a humid night, delivers more water than the coil can deal with; the frost thickens, air stops passing through the fins, and the zone warms while the unit runs hard. The note on frost in a wine unit covers what you can see and safely do. Never chip at it: a punctured coil turns a door problem into a sealed-system one.

Cold coil, warm zone

A clean, cold coil still needs air driven across it. A fan that has stopped is high on the list whenever one zone runs warm, and a stalled evaporator fan leaves its zone with frigid fins and warm bottles. A zone that is warm while its coil is cold and clear points us that way.

When the coil itself has failed

An evaporator that has lost refrigerant is the rare case. Sub-Zero’s warranty lists it with the compressor, condenser, drier and connecting tubing as the sealed system. A coil that stays warm, or frosts in one corner only, while the compressor runs is what sends us to the gauges, under EPA Section 608 certification. That work is booked as a wine storage repair and priced after the diagnosis.