A diagnostic catalog of the causes & cures of of dimming light fixtures or flickering lights & power losses.

How to diagnose the causes of flickering or dimming lights at or in buildings.

This article gives simple diagnostic steps that a homeowner can do to determine the type of electrical system problem that is causing flickering or dimming lights or intermittent loss of electrical power. We list the common causes of these problems and suggest what to do about them.

Watch out:  flickering or dimming lights often indicates a dangerous condition. Switch off the bad acting appliance or circuit and ask for help from a licensed electrician.

Flickering lights traced to bad utility company neutral wire

Watch out: flickering or dimming lights at a building may indicate a dangerous condition, risking fire, shock, injury or worse. The safest approach is to turn off electrical circuits or components that are causing flickering or dimming or acting strangely in any way.

(Nov 10, 2015) Phil said:

I've been searching and can't find the answer to my problem. All of a sudden (last couple of months) my lights go dim whenever an appliance cycles on. All of them. Even when the coffee maker cycles on and off you can see it happen.

The lights even flicker to the cadence of the washing machine during the wash cycle. The dryer is the worst as the lights go waaay dim, but only for a second or two.

I have no electric heat, a 100 amp service with nothing special in the house requiring anything more than 100 amps. I have a well pump, septic pump and a freezer and all the normal things a house would have requiring intermittent electrical draw.

Nothing special, but why are my lights flickering upon appliance demand all of a sudden? I do have some electrical experience and would like to know some simple troubleshooting I could do before calling in the experts, and the power company etc. Thanks.

Reply: Look for what changed in the electrical system, look for aluminum wiring

Phil,

As you are describing what is a new problem, not one that has been present since original construction, I infer that something has changed. Most likely there is a loose connection or a failing appliance.

The fact that it's "any appliance" is puzzling as I don't expect all appliances to be on the same individual electrical circuit.

Check this for me: take a look at the circuit layout in your electrical panel.

If the flickering only occurs when appliances run, let me know how those appliance circuit breakers are located in your panel. For example if they are all on just one side of the panel that would be diagnostic (and would point to a problem in the panel itself).

While you're there see if you can see any aluminum wiring, and let me know the brand and model of the electrical panel.

Reader follow-up: flickering appliances or lights on more than one electrical circuit

(Nov 11, 2015) Phil said:
None of the appliances are on the same circuit. The washing machine and septic alarm are on one circuit/one breaker, the refer. is on one circuit/one breaker, as is the dishwasher, septic pump, water pump, dryer, and range. I did observe that the range has alum.

wiring which has been treated with a type of grease at the breaker connection. The coffee pot is on my "kitchen receptacle" circuit, but shouldn't be an issue in my opinion. I've checked and re-checked every connection in the panel and all are tight and in good condition.

Washing machine, septic pump and water pump are on the left side of the panel, while the refer, dishwasher, dryer and range are on the right. The panel is Westinghouse and all the breakers are too. The freezer is on the basement receptacle circuit. Hopefully, this doesn't confuse you.

Reply: check the incoming service entry wires

As you're seeing flickering across multiple circuits I suspect the problem is

1. in the panel, a bad connection at the incoming service wire, neutral or hot, or bad connections of breakers to bus - since I don't know of defective breaker/bus issues specific to Westinghouse (and haven't seen many of those) I'd look with care (watch out you can be killed touching anything in the panel) at the connection of the mains and neutral to the main lugs in the panel - a job for an electrician.

An example of that problem is at
inspectapedia.com/electric/Electrical_Neutral_Lost.php

The SEC wires coming into the panel are secured in (in some brands) an aluminum lug with a steel screw or set-screw. The screw can feel tight because it's binding in the lug but it might not actually be tight on the wire.

If all of the bad-actors happen to be fed from breakers that pick up one of the two 120V sides of the panel that'd point to the culprit.

If the bad actors are on both sides of the panel the problem can also be outside: e.g. a buried (UF) service entry cable that's damaged or other damage to the utility company's SEC wires or overhead wires or even a pole transformer

Reader follow-up: hiring an electrician to check the panel for cause of flickering lights

Nov 12, 2015) Phil said:
Ok, I'm gonna hire an electrician to troubleshoot the panel, although it appears to be ok it my estimation. I have to start digging somewhere. I will let you know the outcome.

(Nov 16, 2015) Phil said:
My estimation was right. The panel is sound, very clean in the electrician's opinion. Took off every breaker and inspected them, all ok, very tight connections to the bus bars. Measured the power coming in and it was 120v on both legs. I'm miffed.

Reply: check the service neutral

Phil:

If the panel seems OK I'd expect the electrician to start working outwards from the main lugs that connect the service entry wiring to the panel and onwards;

I've found, for example, that the service neutral was disconnected and the panel was "working" through its local ground path - a dangerous condition.

Reader follow-up:

(Nov 19, 2015) Phil said:
Everything in the panel is satisfactory. There are no problems with the service neutral. Panel is 100% good.

As I sit here around 5:00 AM the only things running are my pellet stove (about a 200 watt draw), and 2 lights, and they continue to flicker with each cycling of the coffee pot going on and off. Oh, the refer. is going on and off too causing much flickering.

Reply: check the panel again or look outside the panel

Phil

As flickering lights are occurring on two different circuits I'd want to trace back those circuits to their origin, either in a shared junction box or in the panel.

I would look for a loose connection, aluminum wiring, or a problem in the panel that was not at first so obvious such as a poor connection of the panel neutral to the bus.

It would help to know the panel and breaker brands, and also to know if any aluminum wiring is present.

OR the problem is outside the electrical panel as suggested earlier.

Reader follow-up:

(Nov 20, 2015) Phil said:
I'll attempt to trace back the circuits. Could take a while.....No aluminum, other than the SEC. The panel is Westinghouse and all the breakers are too.

Reply: check the SEC (service entry conductors) wiring

(Nov 21, 2015) (mod) said:
Phil the SEC could be the problem: particularly if the binding-head screws in the panel lugs are not really making sound contact with the SEC wires.

In some electrical panel, tightening the screw binds in the lug and you think it's tight on the wire when in fact the wire is loose. An electrician, who knows how to do this without being killed, might pull the meter, then remove and re-make the SEC connections.

Reader follow-up: flickering light problem found: bad neutral wire from the utility company

Had the local power company here yesterday. They installed a device in the meter socket that simulates a 1500 watt draw, and then measured the voltage on both legs. One side was 135v and the other 108v. That prompted him to check the transformer at the pole.

Transformer was fine, but found that the aluminum ground wire on the cable assembly from the pole to the house was 99.9% severed, with only one strand of aluminum left holding on.

They replaced the cable and VOILA, no more issues. My question now is
: What would have happened if it was 100% severed?

Reply: effects of a lost neutral at the SEC

Thanks for this important feedback, Phil. I've come across this issue before and have described it at InspectApedia.com in an

article LOST NEUTRAL Shocks Homeowner - found at inspectapedia.com/electric/Electrical_Neutral_Lost.php

What happens is this: if you lose the electric utility's neutral AND if your panel is properly installed, you still have a local connection to earth - to ground - at your building. IN the panel where neutral and local ground are tied together, all of the neutral wires in all of your circuits continue to work but all of their return current is flowing out on the local ground.

Watch out: a lost neutral or bad electrical grounding are both very dangerous. Once the neutral has been lost the ground system will be doing work it's not designed to perform.

If there is anything marginal about the local ground - which is common - you can have flickering lights or even overheating and burn-ups on individual ground wires or circuits in the home.
Ultimately the result is very dangerous as loss of safe grounding can result in someone being electrocuted.

...

Continue reading  at LOST NEUTRAL SHOCKS HOMEOWNER for details of this problem, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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FLICKERING LIGHTS, LOST NEUTRAL at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to ELECTRICAL INSPECTION & TESTING

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