Originally Posted by RamblerGuy
Where did you get the information that the gas burner has more BTU'S than the electric heater? I haven't seen it.
I Googled a tech spec sheet showing a Dometic RM1282 inputs 2080 BTUH of propane. Assuming it's about 70% efficient at converting the energy input into cooling capacity, that would give about 1400 Btuh of cooling on gas.
Same sheet shows electric heater is a 210W heater. This converts to (210W x 3.4 Btuh/W) 714 Btuh. The electric heating element is probably close to 90% efficient, so about 643 Btuh of energy goes towards refrigeration.
So the gas provides about 2.5x as much cooling effort.
However, both the gas burner and the electric cycle on/off as controlled by the thermostat.
If the heat entering the food section (for this refrigerator) was less than about 643 Btuh, both can keep up, but the electric heating would be on for 2.5x as long as the gas burner would.
If the heat entering the food section was more that 643 Btuh, the electric element could not maintain temperature. The gas could maintain temperature as long as the heat entering the food section was less than about 1400 Btuh. Above the 1400 floor neither source can maintain box temperature.
All the other reefer specs I saw had about the same ratio between the gas input and heater watts.
Here's my take-away. If I start with a warm frig (or load it up with warm product), and I want it rapidly brought to set temperature - I should run the frig on gas. Once I have the box and food cooled, the electric should be able to hold it.
I'm going to take a look at my (RM135) manual and see if the "AUTO" control will monitor box temp and if it sees the electric is not holding temp, will it cut on the gas.