I wrote this a few years ago but most of it still applies. In my sig is the link to my frigidor build if you want to check that out.
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The Wine Cooler:
People say that any old wine cooler or refrigerator will work but in my experience that isn’t true. Size is very important as I found that humidity fluctuates very rapidly in a small fridge when opened and also when the compressor comes on which is obviously not good for the cigars. I have a 16 bottle right now and regretted it almost the day I bought it. So I suggest at least a 28 bottle to anyone considering building one of these.
The next thing is the compressor. Compressors are noisy but most importantly draw humidity out of the air. I couldn’t keep the humidity above 37%. The condenser plate also collects water and could damage your cigars. Even if you have a drip collector you may end up introducing humidity faster than it can evaporate out of the drip tray. To remedy this I suggest either using a thermoelectric cooler. These have fans inside that blow air across a heatsink attached to a cold plate, which in turn cools the interior. These are less noisy and don’t draw humidity out of the air. Wine connoisseurs like them because they don’t vibrate the sediments in the wine while it’s aging.
You can build your own thermoelectric element like I did for the new fridgidor I’m building but I have to say I might as well have saved the extra money for a ready-made cooler. I probably all told spent over $100 on the improvised unit and will have to cut a hole in the fridge to install it. So in hindsight it wasn’t really worth it. I will most likely buy a thermoelectric fridge and use the unit I made for my pipe tobacco in my old (still current) fridgidor.
Next the lining:
This is not necessary but helps to discourage beetles and also helps to regulate humidity. If you plan on storing boxes, that cedar should be enough. I’m just doing it for aesthetics. However, remember that it must be Spanish cedar or Honduran mahogany. Anything else may impart a bad taste into your cigars. Whether you line it or not though, you should put some form of spacers on the bottom as mold could grow on the bottom of boxes as moisture could gather there.
The shelves:
The stock shelves that most wine coolers come with will not work for cigars and take up far too much room. Wire closet shelves cut to length can easily replace these shelves. Some hardware stores will even do this for you. Other things can be used but they should allow for air circulation.
Wiring for electronics:
If you install any electronics such as fans (important in bigger coolers) or an active humidifier you’re going to have to route the wires. You could just drill a hole but that would leak humidity if not properly sealed. A hole in one with insulation or sealant sticking out also wouldn’t be very attractive.
So one solution is to use a preexisting hole. In thermoelectric coolers the unit is usually somewhere on the back mounted into a hole. What others have done is remove the cooling unit and run their wires through that opening and then reinstall the unit. You’d most likely have to cut a small notch for the wires but that would be hidden. Another solution is to use a power jack and plug. Wire the jack into the power source and the plug onto the electronics’ wiring. Then just mount the jack into a hole drilled into the fridge. You’d have to be precise in the drilling so as to not create a mess and a potential leak. Soldering would most likely be required so unless you’re mechanically inclined I wouldn’t recommend this.
Temperature Control:
The thermoelectric unit will do the actual cooling but only within a certain range as the internal thermostats are programmed for wine storage, not cigars. The high end of this range on many fridges is too cold for cigars so you have to get the unit to come on at a higher than normal temperature.
You can do this by using an external thermostat. These are available from the brewery industry. People use these in refrigerators to ferment beer at consistent temperatures, as beer also requires a higher temperature to ferment than most refrigerators are capable of. They work with a sensor probe, thermostat, and plug. You simply plug the refrigerator into the thermostat, plug that into a power source, place the probe inside the fridgidor, and dial in the desired temperature. These work by only supplying power to the refrigerator when it needs to come on, which is determined by the probe. This way, you bypass the inadequate stock thermostat.
This pretty much is all you need to know to build your own fridgidor.
If you have any questions on sources or anything else, feel free to PM me.