WELL, I am assuming your talking about filling a motor home....if so, the re-filler is supposed to close the valve on the tank during filling. In that case, your Refer should be off, so you don't throw a "code".
as Ken has stated the valve has to be closed before refilling the tank. I shut all appliances off when refilling the propane as well as when filling up the gas tank. It is just a safety factor.
In my case, the refer is almost directly above the propane fill. When on the road (or pulling into a propane refilling station) the refer is operating on gas. When operating on gas, it has an open flame. Open flame plus propane fumes = bad things happening. It is not going to warm up that much while the attendant refills my tank. . . not near as much as catching on fire would warm things up :laugh: