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The best way to go about this would be to verify connections before you hook them up. In general, the House wiring is Black is Positive (+), White is Negative (-), at least on the 3 RV's I've had. With the Genny, Red should be (+) and Black should be (-).
You can double-check the wires by looking for a short to the chassis. At least one of the (-) wires should be grounded to the chassis. The Genny (-) wire is almost always connected to the chassis of the genny (starter motor case is negative).
Also, you can try running the converter and looking for DC voltage polarity on the house wiring, but be careful and turn off all DC operated appiances like the fridge, some of these can be damaged by running old style converters without batteries.
Stewart, Brenda and kids
2008 Newmar Canyon Star 3410