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A customer of mine bought a 10 year old house. When any appliance (or power tool)is initially turned on the lights in the entire house dim for about 2 seconds. There is a 200 amp service box with several spaces open for additional breakers. Each leg in the service box has and equal number of breakers and the amperage on each leg is the same. the house does not have aluminum wire. The voltage at the outlet is 120v. any ideas?
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Some dimming can be normal. The farther from the service transformer and the larger the load that is being switched the more normal this is. That said.
1) Have the power company check the service. They should attach a dummy load in place of your meter. This should check everything from the meter to the transformer. Sometimes a damaged service drop, especially the neutral, or a bad connection at the transformer will make a normal voltage sag much worse. Most power companies will do these check for free.
2) Have an electrician look at the main panel. I find checking the voltage drop across connections will spot bad connections, breakers, corroded buss bars, etc. This can usually be done in less than 1/2 an hour and should be done every few years to prevent larger problems.
3) Assuming that 1 and/or 2 havent yeilded any joy you have a genuine ghost hunt on your hands. An electrician with experience in older houses and who has a reputation for troubleshooting is your best bet.
If it is localized to a single receptacle it could be as simple as a bad receptacle or connection on that branch circuit. Tracking it down is a simple execise in elimination but can be time consuming.
If the problem is present on more than one branch but not all branches, a portable space heater used as a dummy load helps here, check to see if they share a leg in the panel. If they do look more closely at the buss bar connections and one leg of the main breaker. If not you may be looking for two problems and not just one.
By any means be safe. Most of these tests are done with the power on so you may be better off calling a professional. Doctors and morticians both make more money than your average electrician which one do you want to pay.
*Thanks for the ideas, I do recall seeing signs of water entry at some time in the "fuse" box. The busses also appeared to have a white material on them (possible corrision).Thanks again,scott
*Does the ground rod play a role in the dimming problem. I moved into an older home where the panel appears to be grounded to the water main. One day when I was under the house working I could see sparks or some kind of arcing occurring where the panel ground wire attaches to the clamp on the iron pipe. I tightened it all up and the arcing has stopped but I have a similar dimming light problem when a compressor or some other significant load is applied to the panel.I read posts from time to time emphasizing the significance of having a good ground for the panel but still have a hard time conceptualizing the importance of the quality of the ground connection. ie I recall someone writing that the bldg inspector was especially impressed by the installation of three ground rods. What benefits does one reap by being especially well grounded?thanks, karl
*The ground connection is a safety that should only have current flowing in it when there is a fault in the system.IF YOU HAVE CURRENT FLOWING IN THE GROUND CONDUCTOR TO THE WATER PIPE THAT MEANS THAT YOU HAVE A ***PROBLEM*** THAT NEEDS TO FIXED IMMEDIATELY.It could be caused by neutral break on the utility companies side. It could be caused by a break on your side or by a defective or broken wiring in the house.Call the utility company to check there connections and if it is not their call an electrican.
*I will get on the phone monday morning and see what can be discovered about current flowing through the ground connection. I understand basic electrical principles but am still hoping someone can enlighten me as to the benefits of a especially thorough ground connection.Bill, thank you for the "heads up" on a bad electrical condition.karl
*KarlI am not expert on this. One of the purposes of ground/bonding is to make sure that all of the metal is at the same potential, ie "ground". Now "anything" can be used as a ground until current has to flow through it. If the "ground" has high resistance then there will be a voltage drop across it and thus will no longer be at ground.The main grounding source used to the metal water line. But now days that water line might not be metal and even if it is metal from you house, the main might be plastic.So ground rods are also driven into the ground. Depending on the soil that might be or not be a ground ground. That is why in some case multiple ground rods will be used.
*YesI would call the power company. As it affects the whole house it is probably at the transfromer connections or at the connects to the meter. It might be connections from the meter inside. But more likely this is on the power companies side. If they don't find anything then get an electrician out.DO IT KNOW.This could lead to a fire or electrocution.
*scott - Notify the utility immediately as indicated - could be a bad neutral. This should not be happening.
*The power company came out and in a few minutes determined the transformer was too small for the draw and will be changed in the next few days.thanks to all for the input.
*This whole grounding thing gets confusing because there are really two different things going on. One is that you want to have all the conductive metal parts in the system that a person might touch connected to the neutral with a low enough resistance that enough current will flow to trip a breaker the instant a hot accidentally gets into contact with anything it shouldn't.The other is that you want to have a known relationship between the electrical system and true earth ground. You want the conduit and boxes to be at the same voltage as true earth, so there's no way to get a shock between them and ground. You also want a path to true earth ground for lightning or lightning induced currents in the system. This reference to true earth that gives grounding its name has nothing to do with the breaker tripping part of it. A really good ground rod may have a resistance of 10 ohms, and code requires a second rod to be driven if the first checks out at over 25 ohms. But even at 10 ohms, a dead short to 120 volts would only draw 12 amps, not enough to trip any breakers. It would just warm up the dirt around the ground rod a little bit, 144 watts worth.Your system is supposed to be connected to a ground rod at the service entrance, as are your neighbors' systems. The utility company also connects their neutral to a ground rod at the bottom of the pole that has the transformer on it. If corrosion produces some resistance in the neutral line between your service entrance and the transformer, bad things start to happen. Some of the neutral current from your house will flow through your ground rod, through the earth, and back thru the utility's ground or even your neighbors' grounds and their service drop neutrals. If this happens and you have a loose connection at the ground rod, you'll see the arcing that was described. It could come from a bad neutral on your service drop, or from a neighbor's bad neutral.The neutral is what keeps the 120/240 volt system balanced. Without it, or if it gets too much resistance in it, one of your hots will go under 120 volts and the other will go over 120 by the same amount. This is very bad for anything that happens to be plugged in to the high side, like computers or entertainment equipment.The other thing I can think of that should always be said about grounding is that a connection between neutral and ground is required at the service entrance, and forbidden everywhere else.-- J.S.
*Oops -- That should be 1440 watts, not 144 watts.-- J.S.