Ventilation is one of the most important issues to be aware of when installing a low voltage fridge. The more air flow the better.
Compressor Fridges:Most compressor fridges on the market these days have a fan cooled condenser. Like a car radiator, they need air flow to cool the water down, then circulate the cooled water through the system to keep the engine temperature down. Some DC fridges run a static condenser, like the old style fridges with a black wire rack covering the rear of the fridge. Either way, they are designed to remove the heat from the system as it cools down your
Most DC compressor fridges have a circuit for a cooling fan, even if they are operating with a static condenser. In most cases you can run at least two 120mm 12 volt cooling fans from the same circuit. Normally one is fixed up against the condenser drawing air through the fins. The other can be retrofitted to bring fresh air in or remove the hot air from the rear of the fridge compartment. A normal 120mm 12 volt cooling fan will only add about 0.2 to 0.3 amps the system while it is running so it is not a big deal to add an extra fan. The extra cooling will, in most cases reduce the run time it takes the fridge to achieve the set temperature. This will save power overall.
NOTE: It is also very important to maintain a clean condenser as the built up of dust and lint will block the condenser causing a reduction in airflow. Boats and RVs with carpet and or pets, need the condenser inspected and cleaned more often.
Be carful what fan you buy as some are extremely noisy. DC Fridge sells them for about $50. Best to try the fan out first as a noisy fan will almost certainly disrupt your nights sleep. You can also switch the secondary fan so it can be turned on or off at will. At $50 I recommend all savvy travellers carry a spare fan as it is one part that is prone to failure and can spell disaster if you need to try and find one in a hurry as they are not available in every corner store.
Three way or absorption fridges. Unlike the compressor fridge, an absorption fridge does not normally need a cooling fan but in high temperatures or tropical areas, where they suffer most. The addition of a small cooling fan can reduce the fridge temp in some cases by 2 or 3 degrees. That will make the difference between a nice cold beer or a “just cold” one. A small 80mm or 90mm 12 volt fan can be fitted up around the top section of the fridge, blowing across the cooling fins. Dometic also sell a vent with built in fans that will fit straight into your existing frame. Power can be taken from the 12 volt supply to the fridge and once again, they use very little power. The addition of a switch can be fitted if power or noise is a concern.
The best place for any vent is around the compressor area and at the top of the fridge where the heat builds up. When fitting the lower vent always choose a large size one. This will serve two purposes. One, it will allow plenty of air into the compressor area. Two, it makes for easy servicing or repairs should anything go wrong with your most precious appliance. Having to remove the fridge to work on it can make the job twice as big and sometimes very messy. If dust is a problem then make sure the fitting frame is well sealed. A pressure vent will also reduce road dust entering the vehicle.
These rules apply to all electric, gas and portable refrigeration. Also Boat and caravan refrigeration.