My 110V suddenly went to 240V!
My home is from the 40's, remodeled several times, both good and questionable wiring encountered. Most of the ground is through EMT, some newer NMB (Romex). Experienced two or three short power surges where lights went super bright (i.e. 240). I know what that looks like. By the fourth serge the power stayed at high. Luckily we lost only the blender, could have fried everything 110. The refer and freezer were saved by a faulty loose hot lead in the receptical, which burned up before the appliances.

After calling PG&E (who weren't to blame) we narrowed it down to two or three kitchen circuits that have shorted or crossed white wire. Both the black and the white are hot, not just leak current but full 110. Actually PG&E pumps 120 to 125V into our neighborhood so the recps and lights were actually showing 235 to 250V.

Unprofessionally, the kitchen lights are on the same circuit as several recps. This never causes a problem other than the expected momentary dip in light voltage when some appliance goes on like the espresso machine. Naturally the whites are daisy chained together. This is creating a terribly complicated looping of this extra power and I've been trying to track it down for over a week. I haven't been able to isolate it to one breaker, which indicates to me that the daisy chained white wire is crossed (affecting more than one breaker). Two electrician friends have given advise but no solutions. Installed a new temporary ground to panel, not a ground fault. Cleaned up and checked every connection in the panel, no problems found, not change.

I've been systematically disconnecting every receptacle, both black and white, to try to isolate what I assume is a white wire shorted to a black, maybe by a mouse. Find no burnt recps or connections, some loose wires but once fixed no change. I have about 1/3 of the wires to still disconnect and then I'll start checking continuity to trace each wire. The plan is to abandon the faulty wire set if I can narrow it down to one set. Any ideas on how to find this will be greatly appreciated. I've been wiring stuff for 55 years and just completed a 440 3 phase job at our winery so am very familiar with the details. One thing I like about electricity is that it is logical. This one is testing me.

I've searched many forums on this issue and didn't find anything I didn't already try or know, not that I profess to be an expert or a licensed electrician.

 

Welcome to the forums.

I don't know about that but you need to approach repairing it logically.

You don't have breakers tripping.... therefore you don't have a white to black short. It sounds like you have a multiwire branch circuit with an open or missing neutral. Open your panel.... the MWB circuits are usually on a red and black wire and the breakers are directly above each other.

 

No, they provide 240 ±10% and the 120 ±10% is derived from one leg of the 240. Power isn't pumped it is drawn by whatever is connected.That would trip a breaker or burn out a wire if the breaker failed to trip.Do you have any multiwire circuits?

 

Thanks Ray and PJ.
I have two breaker sets (2-20A singles) that are wired one red, one black. How do I find the disconnected neutral? I'll go back and trace where the separate red and black MWBs go to, maybe locate the missing neutral there. I did identify as the likely culprits these two breaker sets. I assume the culprit white goes to one of these four circuits.

My apologies to PG&E, drawn in, no pumped. And 110 x 110% is 121, which is what my circuits measure.

 

What I don't get is why the white wires read 120 to ground. If one is loose or disconnected how do the others whites pick up the voltage?

 

The power ....110 volts.....goes along the black wire to the light......goes through the light into the white wire....down the white wire going back to the panel box......but...........it comes to an open joint and can not get to the panel..........loose wire connection....could be in a wirenut ...could be loose under a screw.......could be loose pushed into the back of a device.


Now is a good time to tighten all the screws in the panel box...........be careful






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That would be 120 volts in the United States.

 

Thanks John.
I'm about to check all the connections. Already checked the screws in the box and found none loose.

110 vs 120. I've never seen 110 here in northern California, always 120, at least at the wire ends if they aren't too long.

 

120 volts is good.............most have 120

 

Almost fixed. I think the cause was the failure of the recp running freezer and refrig. I had missed connecting one old fabric rapped neutral because it looked like a black. It showed voltage because of the light bridge so I left it disconnected until I got the rest working. It turns out it was the break in the neutral daisy chain back to the box.

Everything works but the main lights, which are on one of the same circuits as some of the recps. I've rechecked those few boxes where multiple connections exist to see if I missed connecting a wire to the lighting, haven't found anything yet, getting too dark to continue. All the help given here has been amazing. The advise made all the difference. Tomorrow I'll check the wiring from the lights back to find the disconnect. I think that is all it can be. It is not the switches as they are low voltage.

 

Probably obvious, but this post intrigues me. I thought I'd chime in.

The two multi wire circuits. Ensure the neutrals at each outlet box are tied together with wire nut and use a single neutral pigtail to each individual outlet.

I'm not sure what this means. What you don't want is to use the outlet terminals to continue neutral downstream. It's OK for the Hot wires, but not the neutral.

Like I said, you probably know this but I've talked to many people that don't.

 

all but one of the recps were wired through the recp. I changed them all to pigtails, both blacks and whites. Thanks for chiming in

 

HANDYONE...........i agree with you about the pigtails on any device, over the years I have learned to make all my connections with wirenuts and pigtail the smallest number of wires to the device. This way,if you never use a device it never overheats and or goes bad.

Ensure the neutrals at each outlet box are tied together with wire nut and use a single neutral pigtail to each individual outlet.

 

If this was where the multiwire branch circuit was split to two circuits and it sounds as if it was, the neutrals are required to be pigtailed with a wire nut. To terminate the neutrals here on the device would be a code violation. Further downstream it is acceptabe to terminate the neutrals on the device.