Here is one for the pros.We have a fairly old house, some circuits still with knob&tube and some of these using neutrals for switching lights which we find common in the older houses, a new service installed not to long ago,and some new branch circuits run during service change. Now here is the problem.Every time a motor starts in the house, dishwasher,disposal etc etc,half the lights in the house go dim and half get brighter for a few minutes.I know some will immedietly start blaming the neutral but I think its more involved in that. Thank you and please give me a few days to respond.
Bright & dim
- Thread starter bond
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charlie
Senior Member
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- Indianapolis
Re: Bright & dim
I don't, call the electric utility. I am betting they have an open neutral.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Bright & dim
Bond if you turn off all the breakers on the "A" leg of the panel and just use a amp probe to check if you have the same current on the "B" hot then on the neutral this will tell you if it is a POCO problem, There will be more current on the hot than on the neutral if it is. If the current is the same then it has to be internal to the house. then start checking shared neutral and boot legged circuits that grab the wrong neutral. But I'm with Charlie It's a bad neutral. It is the only thing that will produce those symptoms.
The reason for that test is if the neutral is bad and the house has a grounding electrode the neutral current will flow back to source through the grounding and less on the neutral. The same thing that will cause a GFCI to trip.
[ October 19, 2004, 08:45 PM: Message edited by: hurk27 ]
Bond if you turn off all the breakers on the "A" leg of the panel and just use a amp probe to check if you have the same current on the "B" hot then on the neutral this will tell you if it is a POCO problem, There will be more current on the hot than on the neutral if it is. If the current is the same then it has to be internal to the house. then start checking shared neutral and boot legged circuits that grab the wrong neutral. But I'm with Charlie It's a bad neutral. It is the only thing that will produce those symptoms.
The reason for that test is if the neutral is bad and the house has a grounding electrode the neutral current will flow back to source through the grounding and less on the neutral. The same thing that will cause a GFCI to trip.
[ October 19, 2004, 08:45 PM: Message edited by: hurk27 ]
karl riley
Senior Member
Re: Bright & dim
Wayne, that sounds like a good test, as long as we know that even with a good neutral you can have a substantial percentage of current returning via the waterpipe to a neighbor's neutral and back to the Tfrmr that way.
It will be more extreme with a corroded neutral, however. I agree that the symptoms point to the bad service neutral.
Karl
Wayne, that sounds like a good test, as long as we know that even with a good neutral you can have a substantial percentage of current returning via the waterpipe to a neighbor's neutral and back to the Tfrmr that way.
It will be more extreme with a corroded neutral, however. I agree that the symptoms point to the bad service neutral.
Karl
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