1 receptacle on 2 circuits ?

While updating some electrical in my home, it was discovered that some of the outlets were 12/2 wiring with 15 amp outlets. I decided to install the proper 20 amp outlets to those receptacles.

Of course I turned off the breaker to the outlet, then tested with one of those plug in testers..no lights. However, once I removed the plate and pulled out the outlet, I tested again with a voltage tester. There are 2 black wires, 2 white wires and the grounds. The white wires were still hot. I found the other circuit and turned it off. I'm just questioning why and/or if this is ok to wire back as is.

For the record, it is apparent someone previously, in an effort to appear updated, went around and replaced a majority of the switches and outlets and even added green ground wires in some receptacles. Obviously not aware of wire gauge or the function of the wiring.

 

Since you are in the U.S. not Canada the receptacles were probably correct. Code permits 15 amp receptacles so long as there are at least two places to plug in so as long as there is more then one half receptacle on the breaker it is okay. If the wiring method is non metallic cable and there is no ground wire adding a ground wire serves no purpose and any receptacles with ground should be replaced by receptacles with no ground hole or a GFCI receptacle. If metal conduit was used or metallic cable with a bonding strip then the green wire is appropriate. If old style BX cable with no bond strip was used it must be treated as ungrounded.

Note when two circuits terminate in the same box neutrals must be kept separate but all ground regardless of circuit must be connected together.

 

Good to know on the 15 amp receptacles and cable types.

As for the two circuit outlet, it's ok to wire it back as it was then? Each white wire on its own terminal, same for the black, and the grounds together? The connection tab on the outlet does not need to be broken?

 

If it is two separate circuits as I wrote:Therefore both the silver tab and brass tab must be removed.

 

I think you may arrived in the middle of a multiwire branch circuit where two circuits share the same neutrals. Once you opened the neutral the second live circuit lost its neutral and the neutral wire would become hot due to a connected load.

The way to determine if this is a MWBC is to look at the panel.... if the two breakers are one over the other then it's very likely. You could further verify by opening the panel cover to see if one breaker has a red wire on it and the other has a black wire on it.


It is possible that two circuits were connected to that receptacle and if that is the case the bridge clips would be broken off the sides.



The reason I don't think this is your case since you said the circuits in the box were dead when you turned off the first breaker.

 

PJmax, the two breakers are not above one another and there are no red wires. Actually, the first circuit that powers the outlet is a 20 amp. The 2nd circuit is 15 amp. All the wires in this outlet are 12 gauge. I don't understand how this 2nd circuit fits in. More importantly, is it safe to wire it back the way it was?

 

What kind of tester was used to determine the wires were hot after you turned off the first breaker?

 

I'd be careful with this until you get all the facts. I think PJ would agree, it is rare to see a receptacle being fed by 2 circuits.

When you say there are no red wires, do you mean inside the main panel? It doesn't matter that there are no red wires in the receptacle box, you need to check the breaker wires.
Also, MWBC breakers might not be adjacent, especially in an older home. If installed properly the breakers will be on opposite legs in panel, but not necessarily adjacent.

 

pcboss, one of those pen type voltage testers that light up and beep when in contact with a hot wire.

 

Handyone, There are no red wires in the panel at all. The breakers are on opposite sides (23 & 8). I had the panel upgraded last spring by a licensed electrician. They did add some new wiring, primarily in the basement that is being renovated, but any other wiring that existed in the panel was simply wired back in.

I do know that one of the cables going into this outlet runs into a junction box that joins 2 other outlets and feed from the panel (circuit 23). The other cable goes to an outlet about 4 feet away but it's on the exterior of the house. Also, the other circuit (8) happens to feed the lights and outlets on the opposite side of the same room as the outlet in question.

 

Then you have NOT really tested for voltage yet and everything we have written so far is based on possibly false information. Non contact (pen) tester are a guess at best and often give false positives due to capacitive charges or induced voltages that have no real power. You need to test with an analog (not digital) multimeter (or test light or solenoid tester). An $8-$15 analog multimeter will do fine for testing. Till you have tested for voltage we are only guessing.

 

The breakers may be on opposite sides of the panel, but they are both fed from the same leg. As long as each circuit has it's own dedicated neutral this is Ok, but the breakers need to be adjacent and have a handle tie installed OR the breakers need to be replaced with a 2-pole breaker since both circuits terminate on the same yoke. Since these are 20 amp circuits and both are terminating on a split wired duplex receptacle, the duplex receptacles needs to be rated for 20 amps.

This is basic stuff, your electrician should have known this.