3 wire sets in outlet, still hot w/ breaker off

[reno3204]

Trying to replace an outlet in an old house. Outlet has metal box, and three ( 3 wire, black, white, green) wire sets entering the box. The way it was wired, one black and white going to one set of screws at bottom of outlet, other two sets going to the other set of screws ( yes 2 wires on each screw). I turned off breaker and confirmed the outlet was not working. Rewired new outlet same way, accept used side screws and back stab slots instead of 2 wires on screws. I added a ground screw to the box ( didn’t have one) and picktailed grounds to the outlet. Put it back together and it didn’t work. Pulled it back apart and got shocked. One black wire is still hot with breaker off. Not sure where the other set of wires go, one set probably goes to a nearby light switch. The switch has one set of wires. Black, white, green if that helps. So questions, why is there still a hot black when outlet is off? Why did I not get shocked when unhooking and re-hooking the wires the first time? How do I wire this back correctly?

 

[reno3204]

Ok found that there is another breaker that controls the second set of wires. So I have 2 line wire sets and one load wire set in the box.

 

[Sponsor]

 

[Reach4]

A multiwire branch circuit (MWBC) is a branch circuit with a shared neutral. You can feed the two hots with a 2-pole breaker. If you use two single pole breakers, the levers should be tied together in some way. I suggest you add MWBC to some searches.

 

[Afjes]

Normally a MWBC will have a 2 pole breaker with a x/3 with ground. In this case the person who installed this just ran two separate circuits to the receptacle, however the tabs on both sides of the receptacle should be taken off so that the circuits remain separated. Wiring a receptacle this way gives you two separate circuits - one circuit for one plug and another for another plug on the duplex receptacle

Also, a proximity pen detector would have come in handy in this case and should be used to test the wires in the box to see if anything is still hot before you stick your fingers in it. I always (especially working on someone elses electric) will shut of the breaker and then stick my detector in the box to be sure there is no power remaining before I go working on the receptacle or switch. This is usually the only time I use one of those pen detectors - only to see if there is still power present in a box.

 

[WorthFlorida]

If the two breakers are next to one another, across both hot leads will be 240v. The second, in your situation the breakers are not next to one another, both are on the same leg, L1 or L2.
On the original outlet, is the side tab for the hot leads broken off? Very common where 1/2 the outlet is control by a wall switch. Generally, both outlets would be on the same circuit.