Two neutrals on separate circuits connected to one outlet

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  #1  
Old 11-30-13, 04:05 PM
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Two neutrals on separate circuits connected to one outlet

I am replacing the wall outlet that my refrigerator uses, and I noticed something odd. I recently purchased my house, which is 35 years old. The outlet has a built-in surge protector, so it has dedicated line and load terminals.

This outlet appeared to have a dedicated circuit. When I switch off breaker #3 in the breaker panel, the refrigerator turns off, but all other outlets in the house remain on. A circuit tester also shows the outlet is off. However, I still received a shock when I touched one of the neutral (white) wires. When I shut off breaker #10, then the wire is dead. Breaker #10 also shuts off some other outlets in the kitchen.

There are two sets of wires in that outlet box. One set (set #1) is a white and a black wire. The other set (set #2) is a white, black, and red wire. The two black wires are capped together. The two white wires are connected to the outlet, and so is the red wire.

I believe that set #2 is the line, and set #1 is the load (connected to the other outlets in the kitchen). The white and black wires of set #2 are attached to breaker #10, and the red wire is attached to breaker #3.

I suspect that this outlet is miswired. I think the idea was to ensure that the fridge is on a dedicated circuit (#3), but is it really dedicated if it's "borrowing" the neutral from another circuit?

I have capped-off the red wire and kept breaker #3 off, and wired the black wires to the outlet instead. Is this acceptable? I think these are all 15A circuits, so I don't know if that's enough for the fridge.
 

Last edited by tabicat; 11-30-13 at 04:27 PM.
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  #2  
Old 11-30-13, 05:19 PM
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It is permissible for two circuits (each with hot and neutral) to be connected to the same duplex receptacle, one circuit to the top, the other circuit to the bottom. Here you need to bend and break off the tabs between the screws on both sides, hot (gold) and neutral (silver).

While the above might not describe the receptacle you have open, it is possible that the above does describe another outlet box somewhere else on one of the branch circuits in question and whoever made up that box did not break off the tabs as needed.

Or maybe two wires in another outlet box are touching where they should not, due to careless putting of the receptacle or switch into the box.
 
  #3  
Old 11-30-13, 05:22 PM
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But the red (hot) wire does not have its own neutral wire. It uses the neutral wire from a different circuit. In order for the circuit to close, I would need to break the tab on the hot side, but leave it intact on the neutral side.
 
  #4  
Old 11-30-13, 05:26 PM
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You may have a "multiwire branch circuit" serving the refrigerator (red and shared white) and other things downstream (black and shared white). This is correct provided you measure 240 volts between red and black (and 120 volts between red and white and 120 volts between black and white.) It's considered "the same circuit" from the point of view of sharing the neutral.

But if this is the case there are still some errors although they may be grandfathered. (1) For the MWBC if the feed and continuing hot wires are tied together directly then the feed and continuing neutrals must also be tied together directly with a wire nut (with a short length aka pigtail going to the receptacle with unbroken neutral tab). (2) The breakers, preferably a side by side pair as a double wide unit, in the panel must have handles tied together which means slots #3 and #10 don't cut it.

The above two rules help prevent getting shocked in the manner you described, from a MWBC.

Getting shocked from an unhooked neutral typically means that the neutral in question is a load neutral (continues downstream) where somehow the hot wire for that circuit or subcircuit continuing downstream has not been de-energized and there is something downstream that is still plugged in and switched on.

Oh, by the way, actually borrowing the neutral from a different cable, even from the same branch circuit, is not correct.
 

Last edited by AllanJ; 11-30-13 at 06:07 PM.
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