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Just bought a house, doing some remodel work in the kitchen. The home was built in 1969, so I'm pigtailing a lot of aluminum wiring terminations with alumiconn connectors. Pulled out a receptacle and discovered the wire configuration shown in the attached diagram. I tested the voltage with my multimeter, and am not sure what to make of the readings (also included in the attached diagram).

The wires do feed other receptacles downstream, but I disconnected all the receptacles and wirenutted all the wires. The multimeter readings in the diagram are with no load on the circuit.enter image description here

Any idea what's going on, or advice about how to proceed?

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    Super common question, we get it every week. That's phantom voltage from your modern digital voltmeter being so sensitive it's acting like a radio receiver and picking up induced voltage from nearby wires. If you connected any load between that wire and neutral, even a night light, the mystery voltage will go away. A clunky old jeweled-movement voltmeter will have the same effect. – Harper May 5 '17 at 17:13
  • Thanks for the fast response, @Harper. Is the neutral-ground voltage also a phantom reading from the digital multimeter, or indicative of a different issue? – tealjos May 5 '17 at 17:30
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    It sounds like neutral is disconnected. If it was tied back at the panel it shoudldn't float like that. – Harper May 5 '17 at 18:07
  • We have a house built 1970 with aluminum wiring (#12 for 15-A and #10 for 20-A 125 V circuits) except the 40-A circuit to the a/c condensing unit and the bare copper wire for the plumbing grounding. Is your panel a split bus? What manufacturer? – Jim Stewart May 6 '17 at 0:41
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Harper is right about trace voltages on disconnected wires it could be anything causing inductance in the wires, but there are few things that concern me.

Aluminum wiring: One of the big problems with aluminum branch wiring is that is has a tendency to loosen up on connections and burn back from the connection point. Then you will be getting weird voltage readings like 57.7 volts. But I don't think this is the case where you have a red and a black reading the same voltage more than likely they have no power connected to them and should be reconnected to the other red and black with 128.4 volts.

You didn't mention if everything was working before you started your pigtail. When you start taking things apart you can start finding things like you have mentioned and we get caught up in chasing ghosts.

Instead of trying to determine each problem as you go along, I would complete the pigtailing first. Then go through and turn everything on and check to see if there are any problems. Look for strange things like a 1 or 2 volt drop between two receptacles that are only say 12' apart. That would indicate a loose connection somewhere. Lights dimming when you turn something on and the circuits are not related. That would indicate a loose or broken neutral. You television only comes on when the dryer is running (true story). Also broken neutral.

Then if you find something acting up you can identify the physical problem and location. Then if you post that problem we can be proactive and not so speculative.

  • Thanks for the advice! I finished all the alumiconn pigtails this weekend, and sure enough, I found neutral on this circuit that someone (for reasons unknown) had just capped with a wire nut. Spliced it into the other neutrals on the circuit, and everything is kosher now. – tealjos May 8 '17 at 15:25
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Also check the neutral bar in the panel. Our tract house was built in 1970 and when we moved into it in 1978 I found that some of the neutrals (#12 AL) were loose on the neutral block in the panel (GE). One had the insulation burned.

The connections of the hots to the breakers were all tight.

I hastily concluded that the neutral bar could not be trusted to keep the neutral contacts reliable and so I pigtailed each neutral with #12 copper. I don't think this was necessary and some inspectors might flag it, but I do not think it is a code violation. We have not had any trouble in the in 35+ years since. Every time I have had occasion to remove the dead front I inspect those pigtails and there is no sign of deterioration. I used No-Al-Ox and either yellow B-caps or red ScotchLoks. Since then I switched to Penetrox A and red or grey ScotchLoks. Now I am changing over to AlumiConn set screw blocks even though I have never had a joint fail.

  • Thanks Jim! It didn't end up being the panel's neutral bus, but there were a few neutral and ground bus connections that I was able to tighten for good measure. I appreciate the advice! – tealjos May 8 '17 at 15:31

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