There are two side-by-side emergency shut-off switches on the main floor of our house. One goes to the oil-fired hot air furnace, and the other went to a stand-alone oil-fired hot water heater. The latter has since been replaced with an electric hot water heater; and the circuit breaker to the oil hot water heater has been shut off since the change over to electric hot water earlier this year. The oil-fired furnace also has a electric shut-off switch for servicing the furnace; as did the old hot water heater. In the basement where both were located, there are double sets of 12-2 coming into a 4x4 octagon box with a red cover and fuse imbedded in the center of it. In the case of the furnace, the wiring then goes down the side of the furnace to a service shut-off switch and into the furnace for its needs. What I don't understand is why the double set of wires to the box? Another double set goes into another box above where the hot water heater was located, but the wires have been disconnected and the red cover with fuse is no longer connected. Any help would might end the confusion.