Big Voltage Dips and Surges - Why? How to fix?


Old 09-30-04, 09:18 PM
Thread Starter
Join Date: Sep 2004
Location: New York
Posts: 24
Question Big Voltage Dips and Surges - Why? How to fix?

The Scenerio: 1500 sq. ft., 40 yr. old house in flood prone suburb with underground service. 120 amp original service panel with all piggyback breakers, 18 separate circuits with dedicated circuits for the big consumers (microwave, frig, etc.) Outdoor air conditioner compressor unit that has been under water once. Basement with furnace and wiring that has been underwater twice, but appears fine (last time was 6 years ago). A neighbor 5 houses away lost their underground service a few years ago and had to replace the underground line (at their expense).

The Symptoms:
Been in the house 25 years. From day 1, when the sump pump (12Amp) runs, the lights on the first floor dim. In recent years, when the garbage disposal gets turned on, the television turns its self off (so now I have a UPS to prevent that). When the furnace kicks on, the bathroom lights burn brighter momentarily. When the toaster oven is on, the lights in the kitchen get dimmer. When the compressor in the garage goes on, the computer in the adjacent room turns off (yet another UPS purchased).

The Data:
When checking the voltage of each leg coming into the circuit panel, leg 1 measures 114.5 V; leg 2 measures 127.7 V. When I run my 15 amp air compressor from the outlet next to the panel (and connected to leg 1 with 114.5V) the V drops initially to 94.2 V (and levels off at 103.5 V) while at the same time the V in leg 2 at the panel jumps up to 135.3 V and stays there until the compressor turns off (ie. a max. voltage difference of 41.1 V or steady difference of 31.8 V betweeen the two legs under load.) Immediately after, V in leg 1 was 116V and in leg 2 was 125.7V. This check was done while there were just a few lights on in the house and a TV on.

Additional info:
The transformer for our end of the street is two houses away. I checked the voltage of the next door neighbor's electrical panel and each leg was an identical 118.7V. There is an electric company above ground connection pod between my house and the neighbors. This has been under water on serveral occasions over the years. I have checked EVERY receptacle with a standard testing device (H-N-G) and all check out fine. Connections at the breakers are tight, similarly at the neutral bars. There is a good ground with the main water supply coming into the house in the basement. Circuit panel is in the garage and has never been underwater.

The Big Question:
What is the most likely cause of this progressively worsening problem? How can you get 135 volts in the other leg when the one under load is dropping to 103.5V??? Underground cable deterioration? Poor connection at the pod? Short circuit? A poor 40 year old main circuit breaker feeding 14 of the 18 circuits? Do I need a new circuit panel of larger capacity and get rid of piggyback breakers? Combination of all of the above? Should the electric company (Rochester Gas and Electric in Rochester, NY) be financially responsible for providing equal voltage in the two legs coming into the service panel? Can they test the adequacy of the cables feeding the main panel? At this point, what is my best course of action?

Many thanks and blessings to those who can shed some light on this problem!
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Old 09-30-04, 09:24 PM
Join Date: Sep 2000
Location: United States
Posts: 18,497
You should have called your power company and reported these problems 25 years ago. Call them now. They will likely come out immediately and fix this in ten minutes at no cost to you. It sounds like a loose connection of your power company neutral. This problem is more common than you think. They probably fix a dozen of these a day.
Old 10-04-04, 10:01 PM
Thread Starter
Join Date: Sep 2004
Location: New York
Posts: 24
Your advice was right on target and VERY much appreciated.

The problem was in the connection pod at gound level that had been underwater several times with the flooding in our area. Also contributing was the galvanic action of the copper neutral line clamped to my aluminum cable going under the driveway to the meter in the garage. Fortunately, that cable and the hot legs were in good shape. The fix took an hour and was on their tab; anything on my side of that connection would be anything but quick and cheap. The linemen were great in giving me an education in the basics of 240V electricity.

Once again, many thanks for your wonderful service and advice, Chuck

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