Brian Baker
Member
- Location
- Basye VA
why would i have 70v line to neutral and 114v line to ground, but other phases equal around 114v line to ground and line to neutral?
208 have 70v neutral to hot on one phase
- Thread starter Brian Baker
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Cow
Senior Member
- Location
- Eastern Oregon
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- Electrician
Because you have a poor neutral connection.
- Location
- Placerville, CA, USA
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- Retired PV System Designer
That alone does not seem to explain both the low voltage to neutral from one phase and normal voltage to neutral from other phases.
It might be a combination of a compromised neutral and an open hot line, measured with a high impedance meter.
It could be a bad neutral alone if the three hot to neutral voltages are being measured on different L-N circuits that do not share the same neutral.
synchro
Senior Member
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- Chicago, IL
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- EE
Have you measured the voltage from neutral to ground?
If you see any significant voltage then I suggest putting a load across these points to see if the voltage goes down noticeably.
If you see any significant voltage then I suggest putting a load across these points to see if the voltage goes down noticeably.
Brian Baker
Member
- Location
- Basye VA
voltage to ground on neutral 12-15v and checking all lines to the same shared neutral just one has 70v reading. .I cant uderstand this when I have 114 to ground on same line. Is something canceling out or something wrong.
THanks to all who comment
THanks to all who comment
LarryFine
Master Electrician Electric Contractor Richmond VA
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- Henrico County, VA
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- Electrical Contractor
Is this with normal loading or unloaded?
synchro
Senior Member
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- Chicago, IL
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- EE
Have you measured the voltage between all 3 pairs of phases (i.e., hot terminals)? They should all be close to the nominal 208V, but perhaps (114V/120)x208= 198V in your case.
If only one pair is at this full voltage and the other two are down near 114V, then perhaps the winding polaritiy in one of the three star-connected transformer legs is reversed (this would be the leg that's not part of the pair that's producing full voltage).
If only one pair is at this full voltage and the other two are down near 114V, then perhaps the winding polaritiy in one of the three star-connected transformer legs is reversed (this would be the leg that's not part of the pair that's producing full voltage).
Brian Baker
Member
- Location
- Basye VA
we took the 4 wire from a conduit in the ceiling and are using it for recepticles. its a short run and I don't think there are any other loads on the circuit. however it goes through a inaccessable area so there is a chance it may be. line to line I have 204,204,206.I am confused never saw this before. Is it possible the neutral is shared somewhere. thinking about just not using the low v to neutral line but is there a concern the problem goes deeper.should I just run a new 4 wire set to the panel or could there be a legitamate reason and the circuit is fine. never saw voltage to neutral low on one lead while others are fine and all are fine to ground. Tommrow I will suit up and see if its the same in the panel.
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lordofthisworld
Senior Member
- Location
- Massachusetts
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I am not sure what you mean by "phase to phase" voltages. The previous post gives the line to line voltages, which seem appropriate for a nominal 208Y/120 four wire supply.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
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- Electrical Contractor
kwired
Electron manager
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- NE Nebraska
12-15 volts neutral to ground is pretty high, I'm still in the bad neutral somewhere camp. N-G should be negligible with no load, and probably only be maybe five or six volts maximum heavily loaded, unless you have really long undersized conductors.
synchro
Senior Member
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- Chicago, IL
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- EE
Another possibility is that the neutral is being created by a grounding transformer (like a zig-zag) from a delta feed, but one of the 3 legs of this transformer is open. The neutral might also be disconnected from ground, or it might have an intentional resistance to ground for limiting fault current but which is allowing a voltage to appear in this case from unbalanced currents.
As GoldDigger said about a poor neutral connection: "That alone does not seem to explain both the low voltage to neutral from one phase and normal voltage to neutral from other phases." Also, an open hot leg in a star connected transformer output can't be a possible cause because all three of the line-to-line voltages are close to 208V. But an open leg on a grounding transformer might be allowing an AC voltage to appear on the neutral that's in-phase with one of the line inputs. Just a guess, since it's an unusual situation.
As GoldDigger said about a poor neutral connection: "That alone does not seem to explain both the low voltage to neutral from one phase and normal voltage to neutral from other phases." Also, an open hot leg in a star connected transformer output can't be a possible cause because all three of the line-to-line voltages are close to 208V. But an open leg on a grounding transformer might be allowing an AC voltage to appear on the neutral that's in-phase with one of the line inputs. Just a guess, since it's an unusual situation.
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