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I've read numerous "flickering lights posts" and the answers range from bad bulbs to bad wiring to a bad neutral. Here's what I've determined:

  • They (the tenants) report it only happens when either the 3D printer or the clothes washer is running, but not the electric stove.
  • It's all the lights throughout the house, and not just the LEDs.
  • Moving the printer to a different circuit didn't fix anything.
  • Even an incandescent bulb on a circuit less than 10' from the breaker panel flickers.
  • The voltage at the panel when not flickering (measured just after the master breaker, hot to neutral): One leg 116.7v. The other leg 124.4
  • The voltage at the panel when they are flickering (hot to neutral): One leg 118.8v. The other leg 126.4
  • The voltage at the outlet of a flickering bulb: 118.8v.
  • Previously we had a problem with the lights brightening when a load kicks in. We had an electrician out who found some iffy neutrals and other unrelated issues. He reseated the neutrals and the problem went away. But that's about when the flickering started.
  • The house was built in 1964 and is located in the U.S.

So my question is: Who do I call next, the power company or an electrician?

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  • Is it an active flicker or more of a dimming situation? Does it happen the entire time the printer or washer is running or just at start-up?
    – MonkeyZeus
    Dec 12, 2022 at 16:27
  • Does it happen during windy or rain/snow situations? It could indicate a failing weatherhead.
    – MonkeyZeus
    Dec 12, 2022 at 16:30
  • It's not affected by the weather.
    – Duston
    Dec 12, 2022 at 16:40
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    @manassehkatz-Moving2Codidact I agree, 5% difference seems pretty high for something coming off a transformer.
    – Duston
    Dec 12, 2022 at 17:06
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    @manassehkatz-Moving2Codidact That's a good idea. She has moved the printer to a different outlet, but I can't say it was on a different leg.
    – Duston
    Dec 12, 2022 at 20:15

1 Answer 1

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I think you had a lost neutral all along

Each house/dwelling has a local Grounding Electrode System aka "ground rods" and the wires running out to them. Each main panel has a Neutral-Ground Equipotental Bond (N-G bond) whose job is to keep neutral near earth potential. This works with the ground rods to keep this from happening (UK homes don't have ground rods).

So thanks to the N-G Bond, there's a party happening in your main panel where house neutrals, utility neutral, house grounds and ground rods all come together. Got it?

enter image description here

So what happens in a Lost Neutral? This, except the neutral connection actually has an alternate path (a bit byzantine but it does work). Your neutral -> your N-G bond -> ground rods -> the dirt -> neighbor's ground rods -> neighbor's N-G bond -> neighbor's neutral.

This path has some resistance, being dirt and all, but still, it will somewhat limit how far neutral will wander away from the center. This reduces the symptoms of a Lost Neutral.

What changed is your electrician "Tuned Up" your Grounding Electrode System to get it performing better. (it was probably broken; given the liability that creates I would have your guy make the rounds to all your properties and check it there).

Thus, all the electrician did is reduce the severity of the symptoms and that seemed like a victory - but the underlying Lost Neutral condition remains.

The power company should fix that for free in most cases.

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  • Upvoted - have to agree, maybe the neutral isn't totally lost but it at least has problems. That's a big difference between the two legs.
    – KMJ
    Dec 12, 2022 at 21:59

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