Icemaker Ice maker -Inst Manual- Fis problems

The operation of the icemaker can be broken down into three cycles; the freeze cycle, the harvest cycle and the fill cycle.

FREEZE CYCLE

The freeze cycle begins after the mold has filled with water. It ends when the water is completely frozen into cubes and the harvest cycle begins. The amount of time spent in the freeze cycle is controlled by a number of factors depending on the individual design, but it is best explained by knowing how the harvest cycle is triggered.

HARVEST CYCLE

The harvest cycle occurs when the ice is ejected from the ice mold. (Figure A-2) The harvest cycle is triggered in one of two ways, depending on whether the icemaker has a flexible ice mold, (flex-tray) or a rigid metal ice mold. (hard-tray)

FLEX-TRAY HARVEST CYCLE

Most flex-tray icemakers harvest ice solely on the basis of accumulated time, or "run" time. Timing is accomplished by a low-rpm icemaker drive motor acting through reduction gears. Every two hours or so of "run" time, depending on the design, the icemaker harvests. However, it should be noted that the accumulation of "run" time is, in one way or another, thermostatically controlled. For example, Admiral-type flex-tray machines have a thermostat in line with the icemaker timing and drive motor that opens at 19 degrees, and doesn't close again till the freezer temperature drops to 15 degrees. Therefore, time only accumulates if the temperature drops below 15 degrees. Whirlpool flex-tray icemakers accumulate time only while the compressor is running, which is determined by the cold control, which is the thermostat that controls the refrigerator and freezer temperatures.

HARD TRAY HARVEST CYCLE

In hard-tray icemakers, harvest is triggered thermostatically. A thermostat pressed against the ice mold senses that it is cold enough to ensure that the ice is frozen. (For example, the thermostat on the late model modular crescent-cube machine closes at 17 degrees F.) When the thermostat closes, the drive motor activates, and the harvest begins.

When the harvest cycle begins in hard-tray icemakers, a heater begins slowly heating the ice mold. When the harvest mechanism contacts the ice, it stalls until the ice melts enough to release it from the mold. Though the surface of the cube does liquefy slightly, it refreezes quickly. Cubes in the bin might occasionally stick together a little bit because of this liquefication, but they should be easy to separate. 

In a hard-tray icemaker, the thermostat starts the harvest cycle, but it does not end the cycle. The mold heater would open the thermostat and end the cycle way too early; long before the mold was refilled. When the thermostat begins the harvest cycle, a cam attached to the drive motor closes a "holding" switch. This switch keeps the drive motor turning until the ice is harvested and the mold refills with water. When the ejection mechanism is reset, the mold is refilled and the cam reaches the proper position, the cam allows the holding switch to open. This ends the fill cycle and begins the freeze cycle.

FILL CYCLE AND FILL VALVE

Towards the end of the harvest cycle, a cam on the drive mechanism closes the fill switch. This switch opens a fill solenoid valve, usually located on the back of the fridge, at the bottom. (Figure A-3) In refrigerators with water dispensers in the door, a dual water solenoid valve is used. One controls water to the door dispenser and the other controls water to the icemaker.

The amount of water that enters the ice mold is controlled by a couple of things. The shape of the cam that closes the fill switch controls the length of time the valve stays open. A flow control washer within the valve adjusts the flow for variations in house water pressure, so that the same amount of water flows through the valve regardless of water pressure. However, if the water pressure is below about 20 psi at the solenoid valve inlet, problems can occur; see sections 8-2(a) and 8-3.