Now we can start. Put your thermometer inside the refrigerator, close the door, and wait about 15 minutes for the thermometer to reach the inside temperature. Open the door (and, working as quickly as you can) read the inside temperature. It will probably be about 40^oF.

Then, unplug the refrigerator’s power cord from the wall outlet. Make sure that no one opens the door for exactly 15 minutes. Finally, open the door and take a temperature reading. You will find that the temperature hardly changed.

Plug the refrigerator back in (its motor will probably come on) and wait another 15 minutes (the thermometer should be back inside).

Now, unplug the refrigerator again, and repeat the experiment. .. but with one difference. Every five minutes open the door for about 30 seconds. When you check the thermometer after 15 minutes, what do you think you will see? That’s right! The temperature has risen by several degrees.

Can you explain why? Right again! Opening the door two or three times let in warm air. Usually, of course, your refrigerator automatically switches on when this happens. But we have unplugged it to prevent the machinery from working.

Plug the refrigerator back in as before, and wait about 30 minutes before you continue. In the meantime, fill your bowl or pot with hot water from your kitchen faucet.

When you are ready, unplug the refrigerator, and place the bowl of water inside (it will start “steaming” immediately). Close the door. Come back in 15 minutes and take a temperature reading.

The temperature will have risen several degrees; can you explain why? I am sure that you can!

Do you have any conclusions? Yep. . . it makes sense not to put hot things inside a refrigerator, and not to open the door often.

One more point: The coils on the back of your refrigerator are designed to transfer heat from the coolant liquid inside to the outside air. To do their job, they must be clean: soot, grease, dust, dirt,and lint all act as insulators, and prevent heat transfer. Consequently, your refrigerator motor works harder — and consumes more energy — to cool the inside contents.

Inspect the coils of your refrigerator (they are called condenser coils) and vacuum out any dust or dirt you find. Make it a habit to repeat the cleaning every three months or SO.