Welcome Larry to irv2.
If it was something added by someone other than mfg of coach it could be wired to your load center, doubled up with another circuit , off transfer switch, some other outlet supplying your water heater.
You may have to crawl into a compartment to trace or follow under chassis.
There are
some links here that may give you a clue.
Some
more 120 info.
Here is a
thread that has some info.