Lights dimming even when nothing is kicking on


Old 03-17-11, 08:11 AM
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Join Date: Mar 2011
Location: USA
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Lights dimming even when nothing is kicking on

I bought my 50s ranch house in 2009. It had a new breaker box and and the only area that had newer wiring was to the room addition. When running the washer or when the fridge kicked on it would dim lights all over the house. The dimming would only last less than a second. I put those on dedicated circuits and that problem has gone away. Then i noticed power tools in the garage would not run well, so added a dedicated circuit up there and all fine.

So it seemed like the trouble was having heavy duty items on the old wiring, but i still have something going on that i can't figure out. I have APC units in the room addition (new wiring) and one in the office/bedroom (old wiring) for the computer equipment. You can hear them clicking on and off because of voltage drops. This can last anywhere from 1 to 30 seconds. I can be in the house with furnace off, not running any appliances, the fridge not running and it will still happen. If im running a box fan in my bedroom or the room addition it will also drop in speed when this is happening. Since the transformer on the pole in the back yard is feeding 4 homes, i thought maybe something is happening there. The power company has been back there once so far working on it when I lost power last year, but they didn't replace it. They sent me a letter telling me they had to work on it and they would be monitoring the issue...

The voltage drops could be unrelated to having to add dedicated circuits. I don't understand what would cause it to drop for several seconds even when nothing is on. I checked for loose connections in the breaker box and found nothing. Not sure if there is still something I can check or if its time to call the power company.

New breaker box was put in 2005.
100 amp service
Old wiring is copper but no ground.
Stove, elec dryer, washer, a/c, furnace fan, fridge, garage outlets (power tools) all on dedicated circuits.
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Old 03-17-11, 08:48 AM
ray2047's Avatar
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The power company has been back there once so far working on it when I lost power last year, but they didn't replace it. They sent me a letter telling me they had to work on it and they would be monitoring the issue...
I would try to get more info out of the electric company about the transformer. if the neighbors are having a similar problem. You might also check with the PUC (state Public Utility Commission) for help.

Do not know if it is relevant to your problem but a friend had a similar problem, even had her service redone. The problem continued even after that and the electric company said there was no problem.

She came home from work one day to find workers in hazmat suits digging up the dead grass around her PoCO pole. Short version very old transformer leaking PCBs The electric company had known the transformer was bad but stalled on putting in a new one because of the EPA requirements and associated cost. The new transformer cured the friend's problems.

Not saying that is happening in your case but if the neighbors are having problems and there is dead grass around the pole you might want to talk to the PUC or your states equivalent.
Old 03-17-11, 08:55 AM
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I think you could give the power company a call to report the power quality issue. It doesn't sound like an emergency situation, but could be a loose connection problem developing.

Four houses on a pole pig transformer does not sound unusual. Your voltage drops could be happening because of a large load at a neighbor's house like electric heat or instant water heater.

You also may need to just adjust the UPS units to medium or low sensitivity if that level of voltage fluxuation is normal for your area. The power company may be able to install a data logging meter to capture 24 hours of what's actually happening, because the UPS tripping isn't accurate enough to get a detailed view of what's happening.
Old 03-17-11, 10:27 AM
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Join Date: Mar 2011
Location: USA
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Thanks. I wondered if my neighbors could be pulling on the transformer causing the drops... No dead grass by the pole. The transformer looks really old compared to some of the others in the neighborhood.

I'll check my settings on the APC. I know one of them I already tried lowering it. If i leave my computer running it will record how many times the voltage dropped.
Old 03-17-11, 10:54 AM
Join Date: Dec 2010
Location: usa
Posts: 243
Is it possible that a shorting circuit could be causing this? I ran into a scary situation about 2 months ago where the daughter in law called me one night complaining about the lights flickering and occasional buzzing from her panel. I went up there and her old Midwest a/c pullout box was shorting out due to someone installing the wire with a cut in it(took a couple of years to act up) and moisture finally got into it. Had to fix it in cold weather as they have a combo Goodman outside furnace and a/c. Might not be that, most likley a voltage drop, but maybe keep eyes and ears open for additional noises etc.??
Old 03-17-11, 06:37 PM
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Join Date: Mar 2011
Location: USA
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No sounds from the panel. Tonight i plugged in a 1000w space heater and the voltage went from 124v to 116v. Checked several outlets in different parts of the house, same 116v. I switch it off and ran the electric dryer which is on a new dedicated circuit I ran and the voltage stays at 124v. Hardly even dips when i turn the dryer off and back on again. Weird how a space heater can wreak havoc. The space heater has never caused the APC to start tripping.

I managed to take care of the issues the home inspector pointed out. Splicing all over the unfinished basement floor joists is now gone, they spliced into a line under the sink to wire the dishwasher and left the twisted wire exposed..., live circuits leading to no where, just cut on one end waiting for someone to touch it. All has been fixed. Only thing left is the attic fan. Its a really bad splice since a wall switch is involved.

I messed up in my earlier post, I think the pole transformer in my back yard feeds 10 or 12 houses. But, im the closest house to it.
Old 03-17-11, 07:27 PM
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Location: Cressona, Pa, USA
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It could be a bad splice in the wall. You never know what was tapped into illegally, and then covered up.
Old 03-18-11, 09:45 PM
wgc is offline
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Location: New England
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You could try looking at the connections and the wiring -- when I was younger I got stuck in an apartment where turning on the AC would drop the voltage into the 90's. I moved out before I figured it out, but I got as far as noticing badly corroded wiring connected to the receptacle (yeah, now I know not to be so patient with the landlord and not to try looking at it myself in a rental).
Old 03-19-11, 02:29 AM
Join Date: Jan 2011
Location: USA
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You say they changed out the old panel, which was most likly an old 60 amp. fuse box, but did they also have the power company upgrade the incoming service line?

Most of our work is on 100 plus year old houses and we get to see all kinds of funky stuff behind walls. Mouse eaten wires, old splices with no juntion boxes, splices in the middle of a wire run where someone just stripped off the insulation and wrapped the new wire around it.
Since you have a new panel box it's time someone ran the new wiring and get rid of those old wires.
Old 03-23-11, 02:47 PM
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Join Date: Mar 2011
Location: USA
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They put in a deck and moved the panel about 30 ft down the basement wall. The power company put in an outside breaker box after the meter, then it runs down a big conduit pipe under the deck and through the foundation wall where the new panel is.

I replaced all the switches and receptacles when i moved in. Didn't notice any corrosion. I may end up rewiring the rest of the house.
Old 03-30-11, 06:51 PM
Join Date: Jan 2008
Location: Mountain View, CA
Posts: 69
I had a similar situation with dimming lights and clicking backup power supplies on the computers. Mostly it happened when other appliances came on, but sometimes when nothing else seemed to be running. When I noticed that some appliances made the lights get brighter, I realized there was a loose neutral. The power company came out and replaced some of the connections to the pole, and the problems all went away. The tech said the flickers when nothing else seemed to be on may have been due to wind moving the lines and irritating the poor connections.

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