I have a single cable that supplied a hot water heater. The black leg is 110 volts and the white leg is 110 volts the third wire is a copper ground. In my main breaker box I have 2 25 amp breakers that are supplying this single cable. What I want to do is install a 110 volt outlet where this single cable is and I change the breakers to supply that outlet. How can I accomplish this?
At the panel, trace this cable to its breaker. Ensure the breaker is in the off position. Take the white conductor out of this breaker and connect it into the neutral buss bar. This bar will have all the whites going to it. Then also remove the black wire from this same breaker. Remove that two pole breaker from the panel. In its place install a single pole breaker of the proper size. Now install that black wire into this new one pole breaker. When this new breaker is turned on, you will have 110-volt power in this cable. Leave the bare ground wire as it is. Plug the open hole with the proper panel blank. At the receptacle end, I would recommend down sizing the wire to match the breaker amperage and the terminals of the receptacle as necessary.
The existing breakers will need to be switched out, from the 2-pole 25 Amp breakers to a single-pole 15 Amp breaker. You will be left with an empty space in the panel. Cover it. Nothing should be able to get in there (eg.; children's fingers). Re-connect the old Black wire to your new 15 Amp breaker and connect the old White wire to the Neutral bus bar in the panel, preferably somewhere close to the new breaker. Leave the bare copper wire where it is in the panel. These existing old wires in the wall (or in conduit) can be kept in place and used to power your new plug outlet. Connect the Black and White wires to the new receptacle as normal. Connect the bare copper Bond wire to the Green screw on the receptacle.