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Tuesday, March 24, 2015

Kelly's Korner - More Mysteries of the Refrigerator

Hey, All,

A couple of weeks ago, I gave you a very simplified explanation of how a refrigerator works, with a promise of more to come.  Well, here it is.

If any of you out there remember spending hours melting, chipping and cleaning ice out of your freezer, you are probably thanking the deities for the development of the frost free systems in our refrigerator/freezers because with the help of technology, we don't have to do that anymore.

As learned in our last session, the coolant (which is very cold now) flows through the evaporator and absorbs the warm air in the freezer.  Because the metal of the evaporator is very cold and the air in the freezer is damp, frost starts to develop on the evaporator coils.  If left unchecked, this ice buildup can cause all kinds of damage.  So a defrost system was developed to periodically turn on and melt this ice.

Mechanical Defrost Timer
The defrost control is the brains of this show.  Every so often,
Adaptive Defrost Control
depending on the manufacturer's setting, this gizmo kicks into gear.  It shuts off the compressor and turns on the defrost heater that begins to melt the ice on the evaporator.  Newer refrigerators may have an adaptive defrost control or a motherboard that does the same thing.

Now the defrost heater starts heating up and melting that ice.  If you stand by your refrigerator when this cycle is in process, you can hear the ice melting and dripping into the drain trough where it goes to an evaporator pan under the refrigerator to evaporate on its own.
Defrost Heater
Now, once the defrost thermostat senses that temperatures have reached a certain limit, it turns the heaters off.  The defrost timer continues on its cycle until the set time has been reached.  Then it kicks the compressor back on and the cooling cycle begins again.
Defrost Thermostat
As you can see, there are a variety of things that may be in play if your refrigerator is not cooling like it's supposed to.  While I am a pretty handy person, I highly suggest you call a service tech to come take a look at your refrigerator.  This is something that I would not attempt to do.  Due to the government's mandate that appliances need to be water and energy efficient, manufacturer's have needed to find newer and better ways to accomplish this, hence the advent of more electronic boards and the education needed to decipher exactly why it is not doing what it's supposed to.  Call your favorite technician if you have problems.

Hopefully, this little tutorial has given you a better understanding on how your refrigerator works.

Have a great week!

1 comment:

  1. Don't forget that the newer refrigerators use thermistors to initiate and terminate defrost. The bi metal works like a safety and opens if the thermistor becomes out of value. The defrost bi metal (limit) usually opens around 140 degrees for these newer systems.

    Great blog post!


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