Everything you need to know about absorption fridges and why adding fans improves performance dramatically and saves fuel

Put in the simplest way adding a fan to your fridge has the same effect as fanning a cup of hot tea – it cools much more quickly, read on for more detail about how it happens.

Fridges cool their contents by absorbing heat from the inside of the fridge and then passing that heat to the air outside the fridge. To get rid of the heat to the air is where the fan comes into play, like the cup of hot tea example, the fan blows the heat away, so it improves the performance of the fridge greatly.

A more detailed explanation about why fans improve the performance of fridges

3-way fridges fitted in motorhomes can be powered by gas, 12 volts or 240 volts, they work in a completely different way to domestic fridges and freezers that we have in our houses. Domestic fridge and freezers use a compressor to compress a gas, that makes the gas hot, the hot gas goes through a long pipe on the back of the appliance where is cools before passing into the ice box part of the fridge where the gas expands and takes heat from the inside of the fridge. The gas goes around a sealed system so it is not lost or used up.

The process is efficient and works very well.

Absorption fridges have a more complex working method, but the effect is the same. The fridge is powered not by a compressor, but by heat in the form of a gas flame or an electrical heater. The refrigerant gas is first heated, then the hot refrigerant is cooled by air before passing into the inside of the fridge where it absorbs heat from the inside of the fridge and so cools the contents. There is a good video describing 3-way fridges and how they work here . . . the description of the working starts at 2 minutes 50 seconds . . .

The important part of the cycle is the cooling of the hot refrigerant gas, that’s where a fan makes a big difference.

Why add a fan to a motorhome fridge

Motorhome fridges work perfectly well without an additional fan, they are designed to be able to work when the ambient temperature is 42°C. However, an additional fan helps to remove the heat that needs to be dissipated and that makes the fridge much colder very quickly. Commercial kits are available containing one or two small fans and a temperature sensitive switch to turn them on and off.

Being a retired chemical engineer I decided that something a little more serious was called for and purchased two computer cooling fans that operate very quietly, the fans are operated by manual variable speed controllers. I have also installed temperature sensors at various places on the fridge so that I can add a microcontroller to fully automate the fans.

These additional fans really come in useful is when we go shopping and return with a lot of food that needs to go into the fridge or freezer, then the effect is really noticeable.

Photos of how much we pack into our fridge

Click to enlarge : captions on each photo give more explanation

Add a fan inside your motorhome fridge

We pack far too much into our fridge – the result is that the air inside the fridge can’t circulate well to cool the contents at the bottom. Usually that means the bottles of white wine, so cooling suddenly becomes really important.

What’s needed is a small fan, plus a long tube that extends downwards at the rear of the fridge. The fan should draw the air from the bottom of the fridge upwards because that’s the natural direction of travel for warmer air whilst cooler air will fall. However, there are practical difficulties putting a tube up the back of the inside of the fridge – the shelves and the sliding bottom drawer. I am working on ideas to solve this and will update the page if the idea comes to fruition.