Converting a Fridge into a Curing Chamber - Part 3 - The Electrics

Having assessed the problems in Converting a Fridge into a Curing Chamber - Part 2 - Controlling Humidity, and acquired the necessary thermostat, hygrostat(s) and relays, there now comes the dreaded time when it all has to be wired together!

My own control box has a thermostat and two hygrostats. There are double plugs controlled by each of these, plus one for normal usage:

Original Wiring for curing fridge / chamber

Whilst I am happy to supply details of the wiring, it's like an explosion in a spaghetti factory, so it's maybe best to look at each element separately!

Obviously, these diagrams are specific to the products I've used. Details of these are in Part 1 and 2 of this tutorial. However, they give a good idea of what's involved and may assist in working out the detail for your own choice of controller. Often the instructions and wiring diagrams supplied by the manufacturer are confusing, and sometimes, not even in English!

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Converting a Fridge into a Curing Chamber - Part 2 - Controlling Humidity

At the end of Converting a Fridge into a Curing Chamber - Part 1 - Controlling Temperature we'd just acquired a hygrometer to check the humidity in our fridge now that we've got it running a 12°C...

...The chances are that the humidity's not at the level we want, but before we start to do something about it, let's just look at what relative humidity is.

When we refer to humidity in percentage terms, what we are referring to is the percentage of moisture in the air, relative to the maximum that the air can hold, at that temperature. Warm air can hold a lot more water than cold air before it becomes saturated, so air at 20°C with 100% relative humidity (RH) will have a lot more moisture in it than air at 12°C with the same 100% relative humidity. Let's make that 'doubly clear': if we cool air, the relative humidity will increase, even though the amount of water in it won't change. This means that the relative humidity of any air we introduce into the fridge will increase as it cools.

Hourly weather statisticsPlaces with different ambient humidity will require different solutions to the problem; the dry of the desert is very different to the wet of the rain-forest.

Don't think that things will be easy because the UK has a temperate climate. Take yesterday as an example: at 7am the relative humidity was 100%, but by 6pm it was only 38% (click the image on the right to see further details). For this reason, control of humidity by the introduction of fresh air using a fan, is unlikely to work here, even though it does in climates with constant low humidity.

So what do we do to control the relative humidity? Well, I suggest that you do absolutely nothing! Instead, go and make some chorizo, or any other salami type product that's fairly thin. Don't spend a lot of money doing it though; it may become a sacrificial sausage later! "Why?", I hear you ask. Well, experience has taught me that drying chambers with salami in them behave very differently than empty ones. Using your fridge to make some salami will give a truer indication of how the humidity will behave.

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