I understand that the 110V that enters an American household is actually half of a single 220V phase. The 110V is derived from the grounded center tap of a transformer before it enters the home. Is it correct to refer to this 2nd leg as the Neutral? It is definitely not a line...
Phase to Neutral 110V
- Thread starter fifty60
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ron
Senior Member
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Both "hots" are ungrounded conductors.
kwired
Electron manager
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- NE Nebraska
Any conductor could be a grounded conductor, we just commonly ground the midpoint (and code generally requires it as well).
We call it neutral because it is equal potential to other points of the system, we also call the mid point of a three phase wye system neutral for same reason.
If you only have a two wire supply system you may have a grounded conductor but technically you don't have a "neutral".
We call it neutral because it is equal potential to other points of the system, we also call the mid point of a three phase wye system neutral for same reason.
If you only have a two wire supply system you may have a grounded conductor but technically you don't have a "neutral".
petersonra
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- Northern illinois
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- engineer
If the system only has two hots, the midpoint of that system is also electrically neutral.
Not all residential systems here are 240/120 though. Some are actually 2 legs and the neutral of a 208/115V system.
Thanks for reminding me of that. For a typical wall outlet, that has 1 line at approximately 110V to a ground reference, and the other line at approximately 0V to ground reference, is it technically correct to call the leg close to 0V when referenced to ground a Neutral? Is it correct to call it a line? Grounded line?
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- Placerville, CA, USA
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If and only if the grounded conductor is the neutral conductor of a 120/240 single phase three wire or of a three phase wye or of a 240 delta with center tapped winding and high leg, there will be a neutral conductor as defined by NEC.
If that neutral conductor is grounded, then the grounded conductor at a 120V receptacle can be referred to as the neutral.
If the service is just single sided 120V, then technically there cannot be a neutral at the receptacle. But there is a grounded conductor, and it must be white or gray color.
Most people will still refer to the grounded conductor as the neutral even when it is not. Less likely to do that in the case of a corner grounded delta, but that is relatively uncommon anyway. Certainly not in the residential context where misuse if the term "neutral" seems to be most common.
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- Retired PV System Designer
But grounded conductor has so many more syllables....
kwired
Electron manager
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- NE Nebraska
As I said before any conductor of the system can be grounded, it just so happens codes usually require the neutral, if there is one, to be the conductor that is grounded.
Take a three wire corner grounded delta system - there is no neutral, but there is one conductor of the system that is grounded.
Regardless of which conductor is grounded that grounded conductor is the one that will read zero or at least near zero when measuring to ground, and that is because it is intentionally grounded not necessarily having anything to do with whether or not it is a neutral.
One could possibly have an infinite number of "phase conductors" if you build such a generator, and if you bring them all in a "star" similar to how a wye system is done that common center point is still the "neutral" of such a system.
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- Placerville, CA, USA
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- Retired PV System Designer
And, just as a curiosity for the most part, a true two phase system will have four ungrounded conductors and a neutral.
Was there ever a two phase supply which used a "square" configuration with no neutral (corner grounded square)? One could always connect a load that way, but was there non-center-point generation?
fmtjfw
Senior Member
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- Fairmont, WV, USA
NEC 2014
Article 100 Definitions.
Neutral Conductor. The conductor connected to the neutral point of a system that is intended to carry current under normal conditions.
Neutral Point. The common point on a wye-connection in a polyphase system or midpoint on a single-phase, 3-wire system, or midpoint of a single-phase portion of a 3-phase delta system, or a midpoint of a 3-wire, direct-current system.
Informational Note: At the neutral point of the system, the vectorial sum of the nominal voltages from all other phases within the system that utilize the neutral, with respect to the neutral point, is zero potential.
A neutral conductor is normally a current carrying grounded conductor in a circuit. In a typical 125V receptacle there are three conductors:
1) ungrounded, hot (any color but white, gray, green, or green/yellow) -- at a nominal voltage above ground, expected to carry current -- typically 125V
2) grounded, neutral (white, gray [or blue in IEC cords]) -- effectively near ground voltage (up a little from ground caused by voltage drop), expected to carry current -- typically 0V
3) grounding, safety ground (bare, green, or green/yellow) -- effectively at ground voltage except under some fault conditions -- typically 0V.
I don't know from first hand experience, but according to the American Electrician's Handbook, generator windings were connected as 3-, 4-, or 5- wire. Three-wire configuration had two windings at 90? and one end of each connected for the third wire. Four-wire had two windings with each wire connected to an end; no common connection. Five-wire had two windings crossing each other at 90?, each end making up four wires, and a common windings center tap making the fifth.
The Handbook diagrams do not show any conductor being grounded... didn't look at other sections or read the text.
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- Placerville, CA, USA
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- Retired PV System Designer
I find it interesting that earlier definitions of neutral point started from the base of justifying the term based on the equal voltage to all other phase wires, then had to move to a pure list definition to allow the word neutral to be used in a high leg delta system.
Then in the informational note, they brought back the functional justification of equal voltage to all other phases with the carefully crafted qualifier "...that utilize the neutral..." to bring the high leg delta back into the fold, allowing the 208 volts from neutral to high to simply be ignored.
Note however, that this assumes, without justification, that nobody will ever use the high leg to neutral connection to get a 208V (close to 240V) circuit that does not require use of two hot conductors, with the accompanying two pole OCPD and two pole disconnect and snap switch issues.
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