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Old 04-04-2010, 10:25 PM   #1
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Lights Dimming

I own an older rental duplex, built in 50's or late 40's. Short occurred in electric stove recently. Since then the lights are dimming occasionally. Tenants called me and I removed neutral wire, and both main feed wires. Installed new main breaker, cleaned main terminal bars in breaker box before installing the new breaker. This made no difference.
I then took out the 120 volt breakers and they looked clean as did the terminal bars they connect to. But after re-installing them the situation changed.Lights were dimming every 5 to 7 minutes and go back to normal after a couple of seconds. Now the dimming only occurs two or three times a day.
All lights in house dim at the same time, leaving me to believe that the problem is neutral related, so I don't see how removing the 120 volt breakers could have made a difference. Local electric company was called by tenant (before they called me). Elec. co. says problem is not on their side of meter.
I tested the incoming voltage on both lines in the breaker box, and both are okay and remain stable when lights dim. (127 volts)
This house had a former tenant who tried to heat it with space heaters. For some reason, there was some damage done to the box as well as the main breaker. I replaced the main breaker at that time (three years ago) and it had shown no further signs of problems
City has no electrical code, and I have done my own wiring for years. But this one has me stumped!


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Old 04-05-2010, 06:54 AM   #2
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Sounds like a loose neutral, possibly at the meter. Could be either the line side or the load side. Could also be at the main panel. Check for use of anti-oxidation compound at those connections if it's done in aluminum wiring. Be careful and always turn the power off when possibly!!



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Old 04-05-2010, 07:30 AM   #3
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Where are you located ?
Did the bus bars or anything else show any signs of damage...arcing ?
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Old 04-05-2010, 07:53 AM   #4
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Are there specific events that cause the dimming, such as starting up of a furnace or clothes dryer?

Sometimes a neighbor's use of electricity can cause the dimming.

Some voltmeters don't react fast enough to measure the voltage change when lights dim for just a second. You would want to include measurements at the big lugs at the main breaker in the panel but this requires an experienced electrician since a slip of your hand can cause a big short circuit and spark. Voltage fluctuations there mean the problem is upstream of that point, possibly where only the power company can get at, (or in the lugs themselves).

Neutral problems are often accompanied by some lights brightening. Brightening and dimming are more noticeable with incandescent lights (traditional light bulbs) as opposed to compact fluorescents.
The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.

Last edited by AllanJ; 04-05-2010 at 07:58 AM.
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Old 04-05-2010, 10:24 AM   #5
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Loose neutral typically has two symptoms. Some of the lights will dim but other will go bright. This does not sound like loose neutral.
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