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#180556 08/29/08 09:10 PM
Joined: Mar 2005
Posts: 49
S
sandro2 Offline OP
Member
I recently was called to a home and the lights were dim appliances were not working.When you turned on switches other lights would dim. Checked the voltage at the meter and 1leg read 120 to neutral and the other leg read nothing.Reconnected bugs and everything was fine.The microwave,clock on stove,tv,telephone and clock radio did not work but I did have 120 at the receptacles. Would low voltage or loose tap connection cause these appliances to burn out?

Joined: Mar 2004
Posts: 947
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twh Offline
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I would guess that you lost a hot. Half the 120 volt circuits work and the other half are in series with the 240 volt loads. I expect that kind of failure to burn out motors and contactors, but that many other types of appliances surprises me. I guess that it must be true, though.

Joined: Oct 2006
Posts: 745
E
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I'll second that. You need to get a true test by disconnecting all loads (shut off all mains) and measure leg-to-leg. If you don't get 240 there, then one of the legs has failed. At that point, your problem would likely become the power company's problem.

What kind of 240 volt loads do you have in this situation? Those will dramatically affect your testing with the power on. If you have an electric stove or dryer, turn them on to maximum and see if your voltage readings change. I'll bet that they will, indicating the failure of a hot leg. You'll still pick up 120V to neutral on one leg, but some wacky voltage on the other leg to neutral.

Oddly, this probably won't do nearly the amount of harm to connected equipment that a failed neutral would. At least the voltage is low and not high as with a failed neutral.

Sounds like it's time to call the power company.


---Ed---

"But the guy at Home Depot said it would work."
Joined: Feb 2008
Posts: 193
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Member
I had never seen a failed utility neutral before. We got a call back on a house we had wired and they had just turned on their power. It was weird. burned up some appiances. different fixtures would come on and dim when different switches were switched. Inconsistant readings at main lugs. We worked for two hours trying to figure it out. Finally called a veteran electrician friend. He knew exactly what it was. Turns out gas company had cut the neutral and went on with their day.

Joined: Mar 2007
Posts: 16
J
Member
It sounds too me a neutral problem.. some lights are dim while others are bright. current is in series with two loads rather than in parallel. you will find different voltages at diffrent devices, depending on there resistance.


jason
Joined: Dec 2004
Posts: 329
I
Member
This exact thing happened to me about 6 months ago, at my house. I was standing next to the TV talking to my wife, when all of a sudden, the surge protector made a popping sound and smoke leaked out of it. I noticed some lights dim and others bright. Probed a few outlets with my meter. 'found some at only 87 volts and others at 180!!!
I ran to the panel and killed every breaker, figureing that I had somehow lost neutral. I went outside to do some sleuthing and noticed the neutral in the service drop hanging down below the transformer. Some tree branches had been blown against the drop by the wind and ripped the neutral out of the pole pig. Kind of scary, but thankfully the surge suppressor was the only casualty. That could have been a very expensive fault.

Last edited by IanR; 09/02/08 08:01 AM.
Joined: Oct 2002
Posts: 482
Z
Member
schenimann, you've never seen a utility fail? Lucky you!

Joined: Mar 2005
Posts: 1,213
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We recently had a perplexing problem where we lost half of a utility high-voltage line. Ended up with two 120V phases and one 64V phase on the secondary of the transformer. Burnt out some lighting contactors and caused no end of confusion as some equipment worked fine, some didn't work at all, and some was simply going nuts. All loads were 1-phase 120/240V fed from the 120Y/208, so every "240V" sub panel off this transformer was having different symptoms.

Joined: Oct 2006
Posts: 745
E
Member
Originally Posted by Zapped
schenimann, you've never seen a utility fail? Lucky you!


Wow, no kidding! When I worked residential service, about 1/4 of our "flickering lights" calls were related to failed underground neutrals on services. I felt kind of guilty for charging the customer for the service call, but at least we reported the trouble to the power company for them by having access to the right departments so that they didn't have to "press one for English, two for Spanish......."


---Ed---

"But the guy at Home Depot said it would work."
Joined: Jul 2007
Posts: 1,335
S
Member
I second your comment.

Being not connected to a grid, every time a raven or eagle desides to sit on a transformer or tries to soar between the lines, out goes the light. A few thanksgings ago, we lost power 4 times in just a few hours. Needless to say, there were some erked turkey cooks, not to mention the cooked turkey in the power lines.


"Live Awesome!" - Kevin Carosa

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