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# Lights Flashing and blown appliannces

#1
04-27-05, 08:31 AM
digital
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Lights Flashing and blown appliannces

When I plugged in and turned on my vaccuum on the 2nd floor the lights on 1st floor started flashing and in the basement my small stereo and small fluorescent light blew up. The breaker did NOT trip. I contacted the local Utility company and the technician found no problem with the 125 amp outlets and on the exterior no problem with Neutral line going to the house and pulled the Base Meter apart and tested it and it was also reading fine. Cann anyone help?

#2
04-27-05, 08:55 AM
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Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
My suspicion is that you have a loos connection somewhere and that you are ending up with 240 volts on certain lines.

It sounds like you are unfamiliar with electricity, and that the power company found nothing. Unless you really want to get familiar with electricity, I would call an electrician.

#3
04-27-05, 05:34 PM
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Join Date: Feb 2004
Location: usa
Posts: 247
Sounds like a bad ground. Without a good, solid reference to the transformers' center tap (which is bonded to ground), the voltages from either end of the winding to "ground" can vary depending on the type of load applied. When you turned on the vacuum (a low impedance, high current device), the voltage (per Kerchoff's Law if you're interested) divides according to impedance. The voltage across the vacuum goes down while the other half of the circuit goes up (your lights and stereo).
Let's say the vacuum on one leg pulls ten amps, and the light on the other pulls one. Therefore, the impedance of the vacuum is 10 times lower than the lights', so ten times more voltage will appear across the bulb than the vacuum (assuming no ground at all).

#4
04-28-05, 03:02 AM
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Join Date: Jan 2004
Location: Oregon
Posts: 1,219
WFO,

You have the concept correct but the names wrong.

In the situation that you describe, the connection to _ground_ is almost entirely irrelevant. What matters in this case is the connection to the _neutral_ of the transformer. If the connection to the neutral is broken, then voltage imbalance can easily happen as you describe it, even if there is a fully code compliant ground connection at both the home and the transformer.

It is true that the neutral conductor in home wiring is connected to ground both at the transformer and at the service entrance, so for these systems the neutral conductor may also be called the 'grounded' conductor. However these grounding connection will not significantly alter the voltage balance between supply legs should the neutral connection fail...with the exception that if the grounding connections are made to shared metallic piping systems between buildings, these _metal_ interconnections can act as backup neutral conductors.

As both racraft and WFO have surmised, this sounds like a loose neutral connection. I'd say that these two circuits are part of a 'multiwire' branch circuit where two supply wires will share a single neutral wire. The neutral wire has become loose somewhere between the main panel and the devices (receptacles) in question.

-Jon

#5
04-28-05, 07:24 AM
digital
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Thank you ALL for the suggestions. I will call an Electrician. But in the mean time, should we be concerned of sparks, fire or other blown appliances?

Thank You

#6
04-28-05, 08:46 AM
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Join Date: Sep 2001
Location: Yorktown, VA
Posts: 322
"should we be concerned of sparks, fire or other blown appliances?"

Yes!

#7
04-28-05, 10:45 AM
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Join Date: Feb 2004
Location: usa
Posts: 247
winnie,
No arguments here. I was trying to get the concept of a voltage divider across and felt that going into "grounded" vs "grounding" would be more confusing than beneficial. Sometimes too little explanation can be equally bad. Mea Culpa

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