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05-31-2010, 09:17 PM   #1
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Electrical problem

I have 240 volts to ground on one phase and 60V on the other phase in a 120/240V single phase system. This happens when I turn all lights on from one location and flip the swithes in other location which one light dims to almost off while another light gets brighter and another light just goes off. The 3-ways are wired correctly and so on.What can cause this goofy situation? I am thinking its gotta be the service cable coming in.Broken wires including the neutral but still nothing is tripping.So how is this possible ??????

05-31-2010, 09:21 PM   #2
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Quote:
 Originally Posted by Bob B I have 240 volts to ground on one phase and 60V on the other phase in a 120/240V single phase system. So how is this possible ??????
It shouldn't be.
Both phases have to add to 240v so with a bad neutral connection you could have 100v and 140v or some other combination, like 80v/160v.

For the 100/140 combo the neutral connection has (140-100)/2 = 20v across it, instead of 'zero.' Then, if one phase was pulling 10A and the other was pulling 8A, there would be 2A flowing through the neutral, with a power dissipation of 2A(20v) = 40w which make for a pretty hot connection.

You are shortening the life of everything that is running on the higher voltage.

Last edited by Yoyizit; 05-31-2010 at 09:26 PM.

05-31-2010, 09:49 PM   #3
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Quote:
 Originally Posted by Yoyizit It shouldn't be. Both phases have to add to 240v so with a bad neutral connection you could have 100v and 140v or some other combination, like 80v/160v. For the 100/140 combo the neutral connection has (140-100)/2 = 20v across it, instead of 'zero.' Then, if one phase was pulling 10A and the other was pulling 8A, there would be 2A flowing through the neutral, with a power dissipation of 2A(20v) = 40w which make for a pretty hot connection. You are shortening the life of everything that is running on the higher voltage.
TY for responding. I understand what you said but why is this happening?

05-31-2010, 09:56 PM   #4
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 Originally Posted by Bob B TY for responding. I understand what you said but why is this happening?
I did turn their main off and feeding this particular apt with the house panel . All lighting works normal.Temp only until I change the SEC.

 05-31-2010, 10:00 PM #5 Member   Join Date: May 2010 Posts: 31 Rewards Points: 25 You most likely have a loose neutral wire either at your panel, the meter/disconnect, or at the utility transformer. The term is called floating neutral as it's not pegged between the 2 phases and floats to wherever the current is pulling it.
 The Following User Says Thank You to fpeftw For This Useful Post: Bob B (05-31-2010)
 05-31-2010, 10:07 PM #6 MXer     Join Date: Dec 2009 Location: South West Coast Posts: 128 Rewards Points: 75 did you mean 240 volt to neutral? If so it is a bad neutral somewhere. If You get 240 volt to ground than you got bigger problem.
 05-31-2010, 10:08 PM #7 Super Moderator     Join Date: Mar 2005 Location: Welland, Ontario Posts: 18,853 Rewards Points: 24,048 Blog Entries: 11 You have a loose or open neutral. The voltage is not being split equally between the two hots. Everything is in series and some devices are getting low voltage while others are getting high voltage. Turn off the power until you get this serviced. The voltage can cause severe damage to your electronic devices.
 The Following User Says Thank You to joed For This Useful Post: Bob B (05-31-2010)
05-31-2010, 10:15 PM   #8
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Quote:
 Originally Posted by 3 legged dog did you mean 240 volt to neutral? If so it is a bad neutral somewhere. If You get 240 volt to ground than you got bigger problem.

most definitly..so its gotta be in the service cable>I'm fixing this prob tomorrow.THX

06-01-2010, 12:29 AM   #9
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Quote:
 Originally Posted by Bob B I did turn their main off and feeding this particular apt with the house panel . All lighting works normal.Temp only until I change the SEC.
Something got my attetion the word apt { apartment } do you own and live in this building ? if not you must get the electrician to come out and deal with it.

The service entrance cable are you using 3 or 4 conductor format if use 4 make sure you land it in proper location you can not get the netural and ground mix up in subpanel location this is circital.

Merci,Marc

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