Does wire length difference create phase shift?

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Discussion Overview

The discussion revolves around the potential impact of wire length differences on phase shift in a 240 volt AC circuit. Participants explore whether variations in wire lengths can lead to significant phase shifts that might affect voltage, particularly in residential wiring scenarios. The conversation touches on theoretical implications, practical concerns, and standards related to wiring.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses concern that differences in wire lengths could introduce a phase shift that reduces peak voltage, questioning the validity of this concern and seeking standards or rules.
  • Another participant suggests that while the concern about phase shift is valid, the magnitude of the effect is negligible at 50/60Hz, estimating that a significant phase shift would only occur with wire length differences on the order of kilometers.
  • A third participant reinforces the idea that phase shift issues are primarily relevant at higher frequencies, indicating that typical house wiring does not operate in that range.
  • One participant mentions that wires are often twisted in a cable to maintain equal lengths and minimize phase differences, highlighting the importance of maintaining the same path for circuit wires to ensure cancellation of external magnetic fields.
  • Another participant notes that previous replies did not adequately address the original questions, suggesting that they have since found answers through further research and consultation.

Areas of Agreement / Disagreement

Participants generally agree that while the concern about phase shifts is valid, the practical implications for typical residential wiring are minimal. However, there is disagreement regarding the adequacy of previous responses to the original inquiry, with some participants feeling their concerns were not addressed.

Contextual Notes

Participants mention the lack of information available on this topic and the potential for misunderstanding due to the complexity of electrical theory and practical wiring standards. There are also references to safety concerns related to wiring practices.

yahastu
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When wiring a 240 volt AC circuit, I've always assumed that it's important for L1 and L2 wires to be the exact same length, in order to avoid introducing a phase shift that would reduce peak voltage. Length differences can accumulate when the wires enter a panel and need to go slightly different places. However I can't find any information about this when I search. Is this true, or am i just being paranoid? is there any standards/ rules about this?
 
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The short answer is that your sort of paranoid. The concept is absolutely correct, but you're way off in magnitude. If we assume that electricity travels at about 1/3 the speed of light in wires (a crude, but not unreasonable guess). Then the wavelength at 60Hz is roughly 2 million meters. So you can make a 1o phase shift if your wire lengths differ by about 5km.

That's why you can't find any info about it. No one worries about this at 50/60Hz. Engineers worry a lot about this stuff at very high frequencies.
 
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@yahastu Basically what @DaveE said.
This would only be a problem if your house wiring worked on the mid Mhz and upwards frequency range, but then we wouldn't call it "house wiring" but "antenna looking like a house"

PS. I hope you took that advice we gave you in the other thread seriously before proceeding as I suppose you are with your "off grid" installation?
 
DaveE said:
The short answer is that your sort of paranoid. The concept is absolutely correct, but you're way off in magnitude. If we assume that electricity travels at about 1/3 the speed of light in wires (a crude, but not unreasonable guess). Then the wavelength at 60Hz is roughly 2 million meters. So you can make a 1o phase shift if your wire lengths differ by about 5km.

That's why you can't find any info about it. No one worries about this at 50/60Hz. Engineers worry a lot about this stuff at very high frequencies.
Awesome, thanks for explaining that. Makes sense!
artis said:
@yahastu Basically what @DaveE said.
This would only be a problem if your house wiring worked on the mid Mhz and upwards frequency range, but then we wouldn't call it "house wiring" but "antenna looking like a house"

PS. I hope you took that advice we gave you in the other thread seriously before proceeding as I suppose you are with your "off grid" installation?

The replies i received there did not seem to address to the questions i asked. However, after doing additional research, and consulting with another electrician, i feel fairly confident that i have found the answers to my questions.
 
yahastu said:
The replies i received there did not seem to address to the questions i asked.
They did, I for one explained why certain ideas you had were dangerous.
Anyway be careful, since it's your house you will suffer from any mistakes made.
 
yahastu said:
Length differences can accumulate when the wires enter a panel and need to go slightly different places. However I can't find any information about this when I search. Is this true, or am i just being paranoid? is there any standards/ rules about this?
You are fixating and overthinking some things, while not realising others.

Wires are often twisted in a cable, so that all conductors will have approximately the same length when the cable passes around a corner of the minimum design radius. The twist puts equal physical tension on all wires in the bundle, but it also keeps the accumulating electrical phase difference the same between conductors.

Once you separate the individual conductors from the bundle, it becomes critically important that the wires of one circuit share the same path through a metal frame, and always pass together through only one hole in a metal bulkhead. The external magnetic fields of the two or three circuit conductors can only cancel if the wires follow the same magnetic path. If the circuit wires were to pass through separate holes in a steel bulkhead, the magnetic field in the material between the holes would be multiple times that of a single conductor.
 
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