The venting of an RV gas/electric refrigerator should be designed to not only provide a place for the warm air from the cooling unit to escape, but designed to actually create a draft that will remove expelled heat as efficiently as possible. Poor venting can cause the cooling unit to overheat and damage the cooling unit.
When the cooling unit gives off heat, it causes air around it to warm. Warm air rises causing cooler air from the lower vent to enter the area and to extract more heat from the cooling unit and also rise. The greater the difference in temperature between the warmer air and the cooler air, the faster the air will rise. Narrowing the path of the air flow forces the cooler air through the cooling unit coils as it rises.
When installing a refrigerator, it's also a good idea to isolate the sides and the top of the refrigerator from the rear, preventing heat from accumulating around the box and hampering the effect of the refrigerator wall insulation.
The roof vent, which caps off the venting, keeps the rain out but allows for good air flow. The roof vent is centered over the cooling unit and is as at least as long as the cooling unit is wide.
In the venting side views below, the roof vent appears to be fairly small. But, in the front view above, you can see that it covers the entire width of the cooling unit.
Below are three examples of good venting under different situations.
It's best if the upper roof vent is top mounted. Sometimes circumstances prevent the use of a top mounted vent, and an upper side vent is the only solution. An upper side vent will work if done properly and only with the smaller refrigerators (5 cubic feet or less). Below are the right way and the wrong way to do this.
RV Mobile Inc. 11715 HWY 99, Everett, WA 98204
The owner of RV Mobile Inc. apparently suffered a heart attack and the original website was shut down.
It has been reposted here to preserve this wealth of information RV refridgerator information.