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Introduction
Adaptive defrost control for top mount, no-frost (TMNF) models was introduced in GE manufactured
refrigerators in 2005. With the push for more energy efficient appliances, this type of defrost control is
becoming more widespread on TMNF model refrigerators. The conventional defrost timer has been replaced
by an electronic control defrost board. These refrigerators use less electricity by more precisely controlling
the defrost cycle. The adaptive defrost interval will vary from 12 to 60 hours depending on the compressor
run time and door openings. These models still incorporate a conventional cold control for compressor
operation.
Adaptive defrost means defrosting based on the compressor run time, along with door open times instead of
defrosting after a set time (which is what mechanical timer models do). This provides energy benefits.
In normal operating condition, the board simply provides power to the cold control. The cold control turns
the compressor on/off based off of the temperature set point and corresponding cabinet temperature.
The board knows when the compressor is on via the CR input. The CR input is tied to the compressor (cold
control), so when the compressor turns on, the CR input has feedback voltage.
Adaptive Defrost
