I apologize for bump an old topic from the dead, just have a few interesting observations from personal experience, maybe someone will need this information in the future
There are some folks out there who have used digital thermostats to control chest freezers, making them operate as a fridge.
You could do the same with your fridge, operating it as a chiller.
Essentially: you need a digi thermostat and a relay. You can set the thermostat to the desired temp and it'll kick off the relay, thus turning the fridge off. When it warms up, it'll close the relay and the fridge will start chilling again.
Should be pretty inexpensive to do. Depending on the thermostat, you could program it to operate differently at night vs. during the day, though I'm not sure why you would want to do that.
I have two old R12 fridges in an unheated garage and there is a noticeable difference in their operation, summer and winter. But it’s nothing I’m concerned about because they are full of beer; but the temperature fluctuations I can tolerate for a bottle of beer may not be suitable for food.
So, you pays your money and you takes your choice.
There’s nothing to stop you putting your fridge in an igloo, if you want to, but it may not work as well as it would in a nice heated kitchen where it was intended to go..
But here are two plausible reasons why a minimum temperature limit is suggested by manufacturers and may affect the operation.
The first will be familiar to split air conditioning engineers as over condensing.
If the condenser is too cold there is a possibility of the refrigerant gaining too much sub-cooling, reduced condenser pressure and reduced flow through the capillary tubes feeding the evaporator. In other words, there will be a reduction in the machine’s capability to do its work. This may result in damage, long term.
Hydrocarbons (R-600 and the like) obey the same laws of thermodynamics as everything else. Their transport properties are selected to be close to the conventional CFC and HFC refrigerants
The second reason will be familiar to people from the old school of refrigeration who worked on butcher’s cold rooms that were often outside the backs of shops in all weathers. It can affect some types of thermostats (not all, just some) where the temperature inside the fridge is warmer than the temperature outside in the winter. If parts of the stat, say its bellows, are mounted on the outside facia, the gas charge inside the stat can condense in the bellows section at low temperatures and cause it to give very erratic control. This is quite rare, but it can happen, even with a domestic fridge. Good luck!