There’s not a lot to storing a fridge, the main thing is preventing it going mouldy in storage. The easiest way to prevent a fridge going mouldy is by removing the water from the fridge.
An unplugged, turned off fridge is the perfect breeding ground for mould. While the fridge has been running, water has managed to work its way into every nook and cranny inside the fridge. This water isn’t an issue as long as you keep the fridge powered up – its generally too cold for any mould to grow. But once the fridge is off, if you close the door, and leave it dirty on the inside, the mould will come. Faster in hot weather, slower ion cold weather but it will come. Cleaning the crumbs out will reduce the mould, but the most important thing is to get the water out.
There’s two ways we can get the water out. The first is pretty simple – leave the doors open. You don’t need them open a lot, you can just jam a rag in between the freezer and fridge door and leave it cracked a little. Over the course of a few weeks, the fridge will dry out completely, and you can close the doors if you want. The only downside is you have no way of really telling if all the water is out. The longer you leave it, the less chance you will have mould. You can leave the doors open for the whole time the fridge is in storage, however we find that if the fridge has magnetised door seals, these will demagnetise and your fridge won’t seal as well when you close the doors again. Additionally a rag stuffed in to stop the door closing can – over time – deform the seals. Generally leaving the fridge open for a week in hot dry weather will be enough, or a couple weeks in colder weather. I wouldn’t recommend leaving the doors open longer than a month.
If you need to store the fridge longer than a month, a great solution is a chemical dehumidifier generally containing calcium chloride you can buy at you local hardware store or supermarket for less than $10. Silica gel sachets might also work, but depending on how much water remains in your fridge, they are unlikely to be up to the task, and a more expensive option. You can also close the doors early even on a wet fridge if you go down this path provided the dehumidifer is big enough. Buy one for the fridge section and one for the freezer section, and be careful not to knock them over once they’re in place.