Weird electrical problem

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I have a house that's now 18 years old. I am the original owner. On one circuit, I am getting intermittent loss of full power. This is manifested by lights that go dim like when a motor somewhere kicks on. I have a UPS in that room that beeps when this happens, but no tv's, clocks, etc. actually experience a full loss of power requiring a reset. This happens anywhere for 0 to 20 times a day and can last from 5 seconds to 30 seconds and only on that circuit. I have checked all the outlets and switches and replaced a few. I have jiggled appliances and plugged and unplugged everything to see if I can reproduce the effects consistently. I have checked the panel and nothing seems out of sorts. I placed my hand on the breaker and it's not warm. It's driving me crazy. Aside from calling an electrician in (the obvious solution) can anyone help me track this down?
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How about open grounds or neutral??? Do you have a replacement breaker? They are cheap enough. Just for laughs, see if the breaker is properly seated.
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do you have a copy machine or laser printer on the same circuit? I've seen those machines drop the voltage enough to make ups's beep and lights flicker.
s

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m_corbelli wrote:

Hi, Have you checked things(loose connection, breaker seating, work out breaker, etc.) inside the main panel? There is a little gadget you can plug into an outlet to see if all is well. It'll tell missing ground, neutral connection, reversed polarity, etc. Any chance you have an aluminum wiring?
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I did check all the outlets with a tester and got the green light, so no neutral/ground issues. The wiring is copper....
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That sort of check doesn't mean much though.
If you think about how an electrical service is set up, it might be easier to test it. Starting at the transformer on the pole outside, your home is supplied with two circuits. When you plug in a device it is essentially in series with the entire loop all the way back to the transformer.
That loop is the key to testing it.
Transformer
^ ^ | | | outlet | +---||---+ <--- Dimming never seen | | | outlet | +---||---+ | | | outlet X <--- Fault +---||---+ | | | outlet | +---||---+ <--- Dimming intermittent | | | outlet | +---||---+ <--- Motor plugged in here
That is a very very simplified diagram. If you put a tester into the top outlet (closer to the transformer than the fault), it will *never* show a problem. But, if you put the tester into any outlet lower than the fault, it *might* show a problem.
There will be no problem if either the resistance of the fault or the current going through the fault is too small. What causes your dim lights is the voltage drop across that fault. Voltage = Current * Resistance.
So, the reason the tester won't see a problem is that it does not draw enough current itself to make the problem manifest, and it will show a problem *only* when something else is triggering it. Motors cause lights to dim because they draw a huge amount of current when they start. The "fault" in that case could simply be that none of the wiring is large enough to handle that much current! In that case the fault is distributed all along the entire circuit.
In any case, the lights dimming only happen where lights are plugged in *after* the fault location. And then only when enough current is drawn through the fault to make it manifest.
So you could test it by putting a lamp into any of those outlets, wait until you get dimming on other lights... and *then* check to see if that lamp is dim too, and from that determine which side of the circuit from that lamp the fault location is on.
The first place you want to check is right at the entrance to your electrical system, to determine if this fault is in your house wiring or is part of the utility's service. (It could easily be that your pole transformer is overloaded, and the motor causing it is an air conditioning unit in a neighbor's house!)
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Floyd L. Davidson <http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com
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m_corbelli wrote:

This sounds characteristic with a problem that manifests itself with "backstabbed" devices. These have a small contact area in comparison to screw terminals and the spring tension may vary with heat. You may want to rewire each device using screw terminals.
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On Wed, 26 Dec 2007 13:59:46 -0500, "m_corbelli"

Are you sure it only happens on that one circuit? Have you plugged the UPS into another circuit?
You can call the power company and tell them you suspect a loose connection on your incoming connections.
They will come out and tighten their connections at the meter and you can tighten the connections at your panel while the power is off.
The service guy might offer suggestions.
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I actually took the ups out of the loop as the beeping was getting annoying. It's still happening so it's not the UPS itself.
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On Wed, 26 Dec 2007 14:55:35 -0500, "m_corbelli"

That tells you it is not the UPS. That doesn't tell you that only one circuit is the problem.
If it doesn't show up on another circuit, I would put my money on backstabs as someone else has already suggested.
If it does show up again then it is mostly likely the service.
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wrote:

Agreed, but.... could possibly be a problem with the load center panel itself could it not? IE - corrosion on one of the bus bars....?
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wrote:

Yes. The load center commonly has aluminum wire. This is one of the primary causes of a loose connection\\corrosion.
I feel that because the OP has the UPS on only one circuit it caused him to suspect that single circuit. I suggested that he plug the UPS into another circuit as a test.
Switching the UPS would be an easy way to rule out either/or. If it works properly on another circuit then he would know he was correct and track down the problem on the single circuit.
If the UPS does show bad power on another circuit the cause would then be most likely the service from his main panel back to the meter base.
The power company will check their connections at the meter base (for free) and shut down the power so the OP could tightening his panel connections.
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Depending upon the size of your electric service, the usage at the time, and the distribution of the loads in the panel, dimming while motors are starting can be perfectly normal. The fact that this circuit can remain in a dimmed state for a prolonged period of time is not normal. You first want to determine which motors are causing this problem, and which leg of your service they are connected to. If the lights and circuits that are dimming are not connected to the same circuit breaker as the offending motors, which I assume they are not, you need to carefully examine all neutral connections, especially those feeding the service at the service panel, the main disconnect, the meter box, and the overhead service drop connection, or underground lateral connection if applicable.

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I stated that it dropped "like when a motor is started", but no actual motor is starting.
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Then I would look for poorly connected, possibly back stabbed outlets in that circuit, In fact, turn off that circuit, identify all outlets and switches on it, and check each for loose connections

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On Wed, 26 Dec 2007 13:59:46 -0500, "m_corbelli"

How old the UPS?
Check the manufactuere's web site for a FAQ.
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m_corbelli wrote:

Go to the breaker box and swap the wire to the circuit breaker with another breaker of the same capacity.
Does the problem move? If so, the breaker is the culprit. If not, at least you know the problem is in the wiring somewhere.
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Yes, that would make good sense. After rewiring all the affected outlets from the "backstabbed" config to the screw downs, if it still happens I'll try to switch out the wiring in the breaker box as you said.
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On Thu, 27 Dec 2007 19:17:45 GMT, "Mark Corbelli"

Please post a follow-up result/solution.
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m_corbelli wrote:

I had this happen in my garage. I found it after some time. It was an outlet but not one I thought it would be. Seems the electrician FORGOT to tighten the screws in an outlet back down the line on the other side of the garage. I was obvious once I pulled the outlet from the box. You'll have to check them all THROUGHLY.
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