Recent power surge: what really happened?

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  #1  
Old 03-07-06, 10:58 AM
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Recent power surge: what really happened?

Hi,

I have bunch of questions related to household electrics, but I will try to separate them in several threads over period of time so that not to mix different topics in one thread. So, let's start from the begginning...

We moved to our new house in December of last year. The house is not that old -- it was built in 1986. About a month after we moved in, we had a strong power surge: lights started flickering throughout the house, appliances shut off, A/C surge protector caught on fire, etc. Pretty scary stuff. Luckily, both my wife and I were at home at that time. I ran downstairs and shut off the main breaker at the panel to cut off all electricity to the house. I then called electric power company and reported the incident. They arrived couple of hours later and spent another hour trying to figure out what was going on. But based on puzzled looks on their faces I knew it was serious. To make long story short, the problem was with a neutral cable going to the house. In fact, I did not have neutral at all at that time. That's what was causing all these problems. It took them another day to find the problem spot where the neutral was bad. It was a few yards away from the house. Eventually, they replaced the bad cable and the power was restored.

The damage: furnace board died, A/C surge protector destroyed, microvawe gone, doorchime stopped working, wall oven partially not working, ballasts on fluorescent lights fixtures gone, and lots of light bulbs gone bad. Not that bad actually. Luckily, again, most of our electronic equipment was not connected at that time. Homeowners insurance covered most of the repair cost.

Now, a few months later, I am wondering what really happened on that day? Ok, the neutral cable was bad. (It was raining that day, so this could have contributed to deterioration of the cable.) What happened next? Why some of my circuit breakers simply tripped and some (especially the ones controlling furnace and A/C ) did not? I guess it is not a coincidence that most of the damaged items -- furnace, A/C unit, and doorchime -- were on the same circuit breaker that did not trip. Could it be because of the circuit feeding these items (furnace, A/C, and chime) not being grounded? (I replaced a doorhime transformer last wek and I did not see a grounding wire anywhere near the line going into furnace.) Any comments?
 
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  #2  
Old 03-07-06, 11:41 AM
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The ground wire, or lack of ground wire, has nothing to do with this.

What happened is that one leg of your incoming power rose above 120 volts, and the other leg fell below 120 volts. Obviously a few volts either way is not an issue. However, the difference in your case was more than a few volts.

Voltages below 120 volts won't bother many loads. For example, incandescent lights will be dimmer, but that's all. Some electronic equipment MAY get damaged.

Voltages above 120 volts are the problem. Light bulbs, for example, will blow. Electronic equipment may get fried (your furnace board).
 
  #3  
Old 03-07-06, 11:50 AM
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open neutral

My friend down here had a open neutral at his home last year, I suspect that this defect happens pretty often. His happened at a connection point, I'll bet that's pretty typical.
Quite simply, half of your power circuits went too high in voltage, and half went down in voltage. The circuits that went too high will burn out lights, and take out your "surge protector", since they start to conduct at about 150volts. Anything electronic are at high risk, also, especially the power supplies. The circuits that went down in voltage show dim lights, maybe overheated motors.
Pretty simple defect, but can cause a wide variety of problems.
 
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Old 03-07-06, 12:03 PM
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Thanks. So, what are normal defense mechanisms against this common problem and why they did not stop the damage? Shouldn't circuit breakers be tripped by voltage being too high on one leg?

More generally, how do I protect my house against similar incidents in the future?
 
  #5  
Old 03-07-06, 12:12 PM
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Breakers do not trip on high voltage. Breakers trip on high current.

Defense mechanisms are good quality surge devices on your electronic equipment. I don't mean the ones that cost a few dollars, but good quality ones. Or, better yet, unplug your expensive electronics when you aren't using them. Also, pay attention. After a heavy wind, rain or snow storm keep your eyes open. If your lights flicker when they normally don't, or if you see arcing at the pole near your house, or if your wires look like they may not be connected as well, then immediately take action to investigate yourself or to have someone else investigate for any problems.
 
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Old 03-07-06, 12:29 PM
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[QUOTE=racraft]Breakers do not trip on high voltage. Breakers trip on high current.

But doesn't higher voltage given constant resistance implies higher current? (Ohm's Law) I guess the voltage was higher than normal but not high enough to trip that 20 amp circuit breaker that was protecting furnace board, A/C, and door chime, right?
 
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Old 03-07-06, 01:54 PM
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As Racraft wrote, a load center circuit breaker will not protect you against overvoltage. I can think of many reasons why. First, the breakers are not designed to protect loads; they protect wiring. They are "slow" relative to the time it takes to destroy an electronic load, power supply, etc. Even if the breaker were sized just below the load of your sensitive device, it would not trip in time to save semiconductors. I don't think it would even trip in time to save an incandescent lamp. The other "issue" is that switching power supplies draw LESS current as the voltage goes up, unlike a resistive load, like a lamp.
If you have ever heard of an OVP (overvoltage protection) circuit in a powersupply, that is the type of circuit that is fast enough to protect the devices you are trying to protect in your electronic devices. It would need to be designed into the equipment you are trying to protect.
Maybe someone here has heard of a 200 amp rated, 10 millisecond, VOLTAGE trip breaker, UL rated, etc, but I have not.
 
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Old 03-07-06, 03:17 PM
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So, from what the various posts are saying, the broken neutral had nothing to do with the voltage surge or the frying of all of the electronics in the house?

Do whole house surge protectors (installed at the main service panel) really protect?
 
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Old 03-07-06, 05:11 PM
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I hesitate to call an open neutral a "surge" event. I'd call it a wiring defect. A surge protector will not offer much help to a homeowner with an open neutral, since surge protectors are designed to absorb a couple to a dozen watts of energy. An open neutral will cause many kilowatts of unbalance, depending on the loads, and yes, can well cause all sorts of things to break, including the surge protector. To answer the question of "do they work". Well, yes, within limits. Those limits do not include direct lightning strikes or a open neutral.
 
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Old 03-07-06, 05:15 PM
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Originally Posted by fixitron
So, from what the various posts are saying, the broken neutral had nothing to do with the voltage surge or the frying of all of the electronics in the house?
On the contrary. The broken neutral caused the voltage surge and caused the electronics to be fried.
 
  #11  
Old 03-08-06, 08:08 AM
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So, am I understanding this correctly that even surge supressors/protectors are not efficient at protecting the house and its equipment from the "broken neutral" problem? And that there is almost nothing one can do but to rely on a power company doing the best job they can of maintaining the cables to the house?
 
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Old 03-08-06, 08:55 AM
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If the power company supplies you with bad power, there's almost nothing you can do about it. In your case, insurance covered most of the damage. In some cases, the power company will also assume partial liability. If you still have unrecovered damages, you may want to discuss this with them.
 
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Old 03-08-06, 10:09 AM
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Originally Posted by John Nelson
If the power company supplies you with bad power, there's almost nothing you can do about it.
Hmm... That is a little disheartening. In my case, at the end, it all worked out fine (if you don't count two days in the house without heat.) My H/O Insurance reluctantly paid for damages and, in the process, I was able to upgrade my furnace and wall oven. But I heard it is not automatic with other insurance companies. Also, I don't know how my claim will affect future rates the insurance company will try to charge me next year...

The biggest problem I had is with the stance of the power company on this issue. I did of course called them and filed a complaint and asked to be reimbursed for the power fluctuations that were beyond my control and the damage their caused. (That was before I sumitted expenses to the insurance.) But I got nothing with them on this front. Even though they almost immediately admitted that the fault was with a neutral cable outside of the house and that they are somehow responsible for maintaining it, they said that they would not pay me anything for the damages! They said go ahead and complain or even sue them, they are not going to pay. They said they have good lawyers and they will take their chance in court, if the case goes that far. And they did not promise that this would not happen again either! That's what concerns me a lot. If it happened once, it can happen again. And who knows, maybe next time my insurance company would not pay or drop my coverage altogether. That's why I am trying to find ways to protect myself from this happening again...
 
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Old 03-09-06, 08:42 PM
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you might also check with Alpha Technologies in Bellingham, Washington.. they specialize in this type equipment.. and are highly regarded by most telephone companies (which are very interested in your neutral being good, since their ground is FAR superior to the electrical companies ground, and when that neutral goes away, they become a path of least resistance.... ) I've seen wire frames ignite because of faulty neutrals in the field! I've also known people that dang near got electrocuted trying to take a shower and their neutral failed, and guys just about getting electrocuted putting phones in mobile homes with faulty/no neutral, go to install a NID, and zap...
 
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Old 03-10-06, 11:34 AM
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Originally Posted by v1rok
That's why I am trying to find ways to protect myself from this happening again...
Open neutrals are very hard to protect against. Really the only thing you can do it be aware of the warning signs, throw your main breaker and call the power company as soon as you notice a symptom. You'll notice on this board that about every two weeks someone will post a symptom of an open neutral and get 10 replies that say "stop typing and call the POCO now!"

Neutral connections don't usually fail all at once; it gets worse over time and eventually fails completely. Here's the list of things to watch for:
* Brightning of lights throughout house (this is almost 100% caused by open neutral)
* Dimming or flickering of lights throughout the entire house, usually during windy weather
* Lights brightning/dimming when using the electric stove, oven, dryer or other 240V appliance
* Electrical tingling sensations on the plumbing or in the shower
* Any of these count double if your neighbors have similar problems
* Broken neutrals at your neighbors house can backfeed power through the water lines into your house (although this is much more rare than the first three).
 
  #16  
Old 03-10-06, 11:50 AM
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* Broken neutrals at your neighbors house can backfeed power through the water lines into your house (although this is much more rare than the first three).
When I was about 4, my mother got shocked taking a shower. My parents called an electrician, after he got shocked, he called the POCO. The POCO drove several more ground rods at the pole, didn't fix the issue. The problem was a defective water heater ACROSS THE STREET.
 
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Old 03-10-06, 06:41 PM
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Originally Posted by ibpooks
Open neutrals are very hard to protect against. Really the only thing you can do it be aware of the warning signs, throw your main breaker and call the power company as soon as you notice a symptom. You'll notice on this board that about every two weeks someone will post a symptom of an open neutral and get 10 replies that say "stop typing and call the POCO now!"

Neutral connections don't usually fail all at once; it gets worse over time and eventually fails completely. Here's the list of things to watch for:
* Brightning of lights throughout house (this is almost 100% caused by open neutral)
* Dimming or flickering of lights throughout the entire house, usually during windy weather
* Lights brightning/dimming when using the electric stove, oven, dryer or other 240V appliance
* Electrical tingling sensations on the plumbing or in the shower
* Any of these count double if your neighbors have similar problems
* Broken neutrals at your neighbors house can backfeed power through the water lines into your house (although this is much more rare than the first three).

Good advice, but just a couple of comments.
1. An open neutral does not affect 240 volt loads. The loss (partially or totally) of a neutral causes all of your 120 volt loads to become series elements, with the voltage across them varying according to their impedance (Kirchoffs Law, if you want to look it up). The overall voltage does not change, so a hot water heater, oven, etc. is not effected. If they have some sort of 120 volt circuitry on them, THAT might be effected, but not the 240 volt elements.
2. Some lights will get bright, some will get dim. The clue here is getting bright. And this will happen when varying combinations of 120 volt loads are applied, not 240 volt loads. A typical way to test this is to turn on various lights all over your house, then turn on a large 120 volt load (a microwave is a good bet). Watch and see if some dim and some get bright.
3. Surge protection is just that. For surges. Surges typically are lightning or switching surges, which typically last in terms of a fraction of a second. Your bad neutral is a permanent condition and if the surge devices reacted, they certainly burned up due to the length of time involved.
4. The POCO should be responsible for damages caused by their equipment. They can't be held responsible for things beyond their control (lightning), but if they have a bad connection, it's their fault.
5. The POCO is not giving you lip service by saying they can't promise it will never happen again. An electrical connection is a mechnical connection. You can take all the precautions in the world and things will still eventually errode, corrode, loosen, and fail. You drive sensibly and change the oil in your car every 3000 miles, but you still can't guarantee that the engine won't fail. BUT, if their equipment fails, they ARE responsible.
 
  #18  
Old 03-11-06, 01:11 PM
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Thank you all! This was extremely informative and useful. I now completely understand what really happened. All the warning signs were there just like people mentioned: brightening/dimming/flickering lights throughout the house, loss of some 120V devices, problem worsened after usage of microwave, and finally surge protector caught fire. But nevertheless all 240V appliances survived like nothing happened! Right by the book. I wish I knew about warning signs a little earlier. But then, I guess, we probably would not have have upgraded our furnace and double wall oven...
 
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