Temperature Controls-Why are they so wacky?

On cold mornings, my wife Jen, gets into the car, and immediately cranks the heater temperature up to 112 degrees or whatever the highest setting is. She wants the car to get toasty as quickly as possible. I don’t utter a word (because I know when to shut up, most of the time). But the fact is that if she set the heater temperature for her “comfort setting”, about 70 degrees, she would be toasty just as quickly. BTW, she does the same thing with the AC. How come? What the heck does this have to do with refrigerators, heaters, and other appliances with temperature controls?

Most heating or cooling appliances work in the same way, and the way they do what they do, is misunderstood. Does it matter? Well, ya, it does. It does if you want to save energy, have your house or your refrigerator, or your oven, operate at a desirable temperature, if you just like to know how things work, or if you want to not stress about such things. It might even prevent you from calling for service, when things are just operating normally.
Warning: This is kind of a geeky post, so feel free to jump ship here if that ain’t your thing (or if you are simply ‘whatever’).

Let’s start with your oven and your furnace. . . heating appliances. When you set the temperature that you desire, the oven or furnace burner fires up, full on. When your “set temperature” is reached, the burner turns off. I have to say that again, because it’s the key element that a lot of people don’t understand. When the “set temperature” is reached, the burner turns completely off. OFF. It is commonly misunderstood that the burner, whether on a furnace or in an oven, just lowers the heat level or flame to maintain the “set temperature”. A fair number of people will set the temperature way higher (like my wife in the car) with the goal of things heating up faster, then turn the temperature down to the needed temperature when they think it’s time. It’s a reasonable thought. It just happens to be wrong. If you set your house heating thermostat at 68 or at 80, the same thing happens in the furnace. The burner comes on full bore, and stays that way until the thermostat says “OK, you reached the temperature you set”, and the burner turns off. If the room temperature you wanted was 68, then just set it for 68 and let it do it’s thing, OK?

The same thing holds true for refrigerators or air conditioning. Here’s the caution with refrigerators and grocery shopping day. When you have a heavy duty shopping trip (which happens often before a big event), and you load all that ‘not cold’ food into the refrigerator, you might be tempted to crank the setting as cold as possible. It won’t help, so leave it be. The fact is that it can take a few hours to get large amounts of food cold, just after putting it into the refrigerator. In fact, any major change (like large amounts of food) could take all day to get to “normal cold”. Don’t fret and don’t panic. Just know and plan.

I hope this information helps a bit. There are some exceptions to this, especially with recent innovations: Higher end furnaces and AC may have multiple stages, or “Variable Speed” motors and compressors, which actually operate at lower speeds or burner levels, depending on what they determine is needed, through various sensors. Some higher end refrigerators also use “Variable Speed” compressors, so that they may alter their speed as needed, instead of turning full-on when cold is needed, and turning off when the sensor says the “set temperature” is met.

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Rich Johnson June 2017
Photo by: Talgat Baizrahmanov