As any owner of a Liebherr wine fridge should know, you are recommended to replace the air filter cartridge every year. But they are are not cheap: a couple of months ago I bought 4 for £87.64 including delivery from Coolectic Ltd, and you can currently buy one from Wineware for £26.50 plus £5.45 delivery. When you are paying the price of a decent bottle of wine per fridge on filter cartridges every year, it makes you wonder exactly what the purpose of them is, and if you can do without them. Strangely I cannot find anywhere in the handbook, or on the web, that directly explains what their purpose is. There are just vague comments about the filter ensuring that the air remains at optimum quality.
Let me help Liebherr out. I understand that it is important to keep air circulating through the fridge to prevent the build up of mould. And given that the air has to be sucked into the fridge somewhere I would imagine that if the air were not filtered you would get a black mark on the bottles adjacent to the air intake. I can also see that if the filters are not replaced regularly they will eventually clog up and reduce the air circulation. But the filter cartridges also contain activated carbon. The only purpose for activated carbon in an air filter as far as I can make out is to remove odours from the outside air, so I really struggle to understand why that is so important for a wine fridge. If you would be happy storing your bottles outside the fridge from an odour point of view, why would you want to remove odours as the air is sucked in?
So my view so far is that filters may be useful, but I would question the need for activated carbon. My cynical mind suspects that the activated carbon is mainly there to help justify the high price of the filter cartridges. The other reason for paying the high price is that the value of the contents of a wine fridge will typically run to over a thousand pounds, and you would not want to ruin all that for the price of a filter, now would you?
Motivated by an enquiring mind and not a little stinginess, I decided to investigate what I was getting for the twenty-odd quid I was spending on a filter cartridge by sawing open an old one. Here is the result:
At each end is a circle of filter paper that looks and feels for all the world like the filter paper you use in cooker hoods. And the gap in between is filled with 3mm diameter pellets of activated carbon. According to the wikipedia article the technical term is apparently extruded activated carbon. So how much would it cost me retail to get the bits I really need to replace – the paper and the activated carbon?
The filter paper is the easy bit. I could buy 2 sheets of cooker hood filter paper for £2.81 including shipping from Amazon. That would be enough for over 150 cartridges. Activated carbon is more tricky, not least because it is sold by weight, and the carbon in the filter is so light I do not have the equipment to weigh it. However, according to this table the bulk density of activated carbon is 0.26g/cc and I calculate that I would need 31.4cc per cartridge, which would be 8.478g. So in a kilo there should be easily enough for 100 cartridges, and I can buy a kilo of 3mm pellets for £9.85 plus £5.25 shipping, £15.10. I think you can probably see the direction this is heading. I could buy the contents of a Liebherr filter cartridge for around 20p retail, even including the activated carbon that I am not convinced is necessary.
So most of the £20-£25 obviously covers the cost of the plastic and manufacturing. Oh, and profit of course.
All I need to do now is work out how best to reassemble an old cartridge with new contents. I think the easiest thing is not to saw at the flange as shown above, but rather to remove and discard the other end. Then I could insert a disk of cooker hood filter paper, add the activated carbon, and seal the end with more filter paper, holding it in place with tape around the circumference of the cylindrical bit of the cartridge. Or I could simply forget about the activated carbon, and sellotape filter paper over the hole in the fridge, or hold it in place with a bit of an old cartridge.