Sorry, but there is No Relationship between external temps and interior refer temps. THAT SAID. If you park a RV in 100 degree heat and have NO AC cooling the inside and have the refer ON, odds are it will not cool to spec. Same thing with a residential refer. Put that residential in a hot barn or garage and expect the residential to keep things cold will be hard to do. My residential in my old house in the garage in 90 plus heat had a hard time keeping things below 45 degrees. When I moved and was able to put the same refer in a utility room that had AC, it would get below 35 consistently and still does after 34 years. But, there is NO Temp Differential measurement like a AC temp Diff measurement for a RV refer. Using your logic, the only way the RV refer would get below 40 degrees was if the outside was 70 degrees or colder. In Texas 100 degree heat, I get RV refers to 32 to 34 degrees all the time in Customer testing. I ALWAYS have the AC ON to keep the interior below 80 degrees. Doug
