Hi guys heard a lot of talk by some people on another site regarding fridge covers. Are they necessary? Our vents are within our awning so not exposed to the elements....and what is their purpose...
All fridges need to have airflow through their rear radiators. The better the airflow, the more efficiently the fridge can cool - because cooling depends on dumping the waste heat extracted from the food inside (or beer, of course).
In domestic fridges there are spacers at the rear to ensure a decent air gap - blocking the airflow is a major reason why fridges sometimes don't get cold enough.
In MH and caravan fridges, there is usually an external vent, or usually two. The lower vent allows cool air in and up over the radiator, and the upper vent lets the hot air out.
If you have an absorption fridge - most are these days as they can run 12V/240V or gas - these rely on heating to evaporate chemicals that circulate around pipes, and take heat out the fridge. In cold environments, the heating part of the cycle is impaired and the fridge doesn't work too well. This is why fridges have covers for the external vents, usually used below 10C. Of course, since the vents also dump heat from the radiator, the vents kind of limit efficiency - so it's a bit of a balance, and needs judgement as to whether you need to put the vent covers on or not. Be warned though, that when running on gas, the fridge need to dump the CO and CO2 from burning the gas, and a poorly installed fridge, with the external vents blocked, could be harmful.
Conversely when it's very hot outside - as it often is where I am - the vents cannot really cool the radiator down very well (not enough flow of air to get rid of heat - and often the air is 30-40C!). For this reason I built my own thermostatically controlled dual fan extractor for the top vent on our rig. This gives us 2-3C in the fridge and -12 - -13 in the freezer in hot weather, which is about right, and is several degrees cooler than it was without the fans (they are completely silent inside the van and use negligible 12V power, by the way).
I have covers for our fridge and only use one on the bottom when it's below about +5/10------the top ones I will only use when colder (there is a pair for the top)---I will probably never use the top one to allow gas from the burner to escape------maybe on EHU in COLD weather I would fit it.