The truth about your refrigerator and freezer

Have you heard any of these snippets of advice about refrigerators and freezers?

  • A refrigerators is more cost efficient when it’s full.

  • Your refrigerator is much warmer at the top and colder at the bottom.

  • When the seal on your refrigerator begins to decay you should replace the appliance.

Which of these are true and how should you use your appliance to get the best, safest and most cost-effective performance? Let’s take a look.

A refrigerator is more cost effective when it is full

This commonly held view comes from one of two ideas. The first is that the air inside your appliance needs to be cooled by the compressor to attain the correct temperature. The more air, the more the compressor needs to work.

Alternatively, that, solid objects, once cooled to the correct temperature take longer to warm up than air. They therefore less prone to temperature fluctuations when, for instance, they are moved or the door to the appliance is opened.

However, neither of these ideas, while sounding perfectly plausible are true in any meaningful sense. They are both misleading for the same reason.

The same solid objects that take longer to warm up also take longer and more energy to cool in the first place.

For those tech heads out there, this is a function of the first rule of thermodynamics and a phrase you might not have heard since your school days; “specific heat capacity”.

If you want to know more, this page has a good explanation of the topic;

In short, a full refrigerator or freezer is not necessarily cheaper to run.

The energy used will depend on the compressor efficiency, the state of the door seals, how often the door is opened, the ambient temperature outside the appliance and the insulation in the walls of the appliance.

All these factors will have a far greater impact than the contents of the appliance.

Your refrigerator is much warmer at the top and colder at the bottom

The answer to this is; Yes, it probably is.

There are several factors to take into account. Back to physics again.

Cold air is denser. So, if you were to put a refrigerator or freezer thermometer at the top of your appliance and another at the bottom you would almost certainly see temperature variation.

Depending on other factors such as the position of the compressors cooling element, any warm air venting at the top of the appliance and the layout of the shelves.

Cold air travels better where there are no physical obstructions so solid shelves might prevent the cold air from falling.

In general, though the coolest air will be at the bottom. Also in any storage space inside the door, the places where milk and bottles are typically stored.

This is harder to measure than you might think, because the most dramatic way to equalize the temperature is to open the refrigerator door. This causes a small vacuum as well as some eddying of the air currents in the refrigerator, mixing and stirring the air.

So, by the time you check your refrigerator thermometer after opening the door, the temperature variations have begun to equalise as a result of you opening the door.

A bit like trying to “catch the refrigerator out” by seeing if you can open the door without turning the light on.

When the seal on your refrigerator begins to decay you should replace the appliance

This is rarely required.

The door seal is a vital part of the refrigerator and a compromised seal will indeed cause your appliance to either use much more energy or fail to keep the desired temperature.

In most cases refrigerators and freezer seals can be repaired or replaced.  So how do you check for a failure?

The Paper Test

Using five dollar bill or paper of similar weight. Hold the paper against the seal refrigerator side where you suspect it might be compromised then shut the door on the paper leaving yourself enough outside the appliance to grip comfortably.

Then pull the paper.

If you feel some resistance to you sliding it out, the seal is likely fine. If the paper falls out or pulls out too easily, the seal may be compromised.

How do you know for sure if a seal might be broken? Simple.

The Thermometer Test

When using a Comark refrigerator or freezer thermometer, if the temperatures you are reading are consistently higher than normal and this cannot be attributed to changes in ambient temperature outside the appliance, then there is a chance that either the compressor is failing, or the seals are beginning to decay.

This guide will show you how to replace a seal in under an hour.

A quick note on refrigerator and freezer thermostats.

Remember. The temperature you set on the appliances thermostat is not always the temperature it attains in use. The only way to be sure is to use a thermometer.

To ensure your refrigerator or freezer is keeping the correct temperature to keep your food safe, invest in a Comark refrigerator or freezer thermometer.