Two phases to house - loss of neutral
in [Repair]
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From: terryc on 24 Nov 2009 19:10 On Tue, 24 Nov 2009 13:40:46 +1100, Phil Allison wrote: > > ** There is always a good "earth" available - courtesy of the water > mains in the street being linked to neutral at every premises. Is this something new(<40 yrs) in the Standards in Australia? No plumbing link here. Just an earth stake under the box.
From: Sylvia Else on 24 Nov 2009 21:58 Baron wrote: > Meat Plow wrote: > >> On Tue, 24 Nov 2009 11:10:26 +1100, Sylvia Else >> <sylvia(a)not.at.this.address>wrote: >> >>> I have to phases of power supply to my house - so three power lines, >>> two phases plus neutral. >>> >>> I've on occasion wondered what would happen if we lost the neutral >>> line. It seems to me that we'd then have the voltage between the two >>> phases across two sets of appliances, one set attached to one phase, >>> and the other set attached to the other phase, with the two sets in >>> series as a result of their common connection to the neutral wire. >>> Since the two sets are unlikely to represent equal loads, the net >>> result would be a large overvoltage on one set of appliances. >>> >>> My electrician says it's not an issue, but I can't see why. >>> >>> Any thoughts? >>> >>> Sylvia. >> Removing the return leg isn't going to cause problems in a properly >> wired US home. Don't know about the UK. > > The lights would go out ! Domestic properties usually have just a 240v > single phase feed. Usually you would get a single phase running down > one side of the street and another phase running down the other. > I said I have two phases. Sylvia.
From: David Brodbeck on 24 Nov 2009 23:54 kreed wrote: > You are both right and wrong as in the absence of Neutral line, a lot > of the neutral current (imbalance) would probably flow via your earth > stake back to the transformer neutral or to a neighbours neutral via > their earth stake and while its not a perfect situation, imbalance > probably would not be as bad as you might think ? > > Of course, if there is a long run through earth (terra firma) back to > the nearest neutral, the soil is really dry, the earth stake is sub- > standard etc etc it might not work very well. Sometimes, just to make things really exciting, some of the neutral current flows over alternate paths to a neighbor's house. These alternate paths can include things like cable TV shields.
From: David Nebenzahl on 25 Nov 2009 00:17 On 11/23/2009 7:43 PM D Yuniskis spake thus: > Phil Allison wrote: > >> ** In the US and Canada - it is NOT permitted to link neutral and earth >> or plumbing within a premises. > > "*within* a premises". The neutral *is* "earthed" right outside > the home, typically. The Code goes to great lengths telling > you exactly *how* to earth the mains at the service entrance. > > However, this ignores the fact that most residential wiring > is grandfathered into "acceptance". Previously, homes *were* > grounded through their "water main" (e.g., my parents home > has ground at the water meter). Grounding a home's electrical system through the plumbing is perfectly safe, and probably the best way to do it, assuming the plumbing is steel or copper. This is no longer permitted according to the NEC (American electrical code). Why? Because not all pipe nowadays is steel or copper. In fact, one can get into great trouble replumbing part of a house with plastic and severing an old ground connection. > So, you can encounter all sorts of different situations > here in the US (I've even worked on homes with knob & tube > wiring!) I've worked on lots of knob and tube wiring around here (San Francisco Bay area). It's actually a very good wiring system, and in most cases is still perfectly safe and functional 60 to 80 years later. It's permitted to be "grandfathered" in under the NEC, but of course is no longer installed anymore. -- I am a Canadian who was born and raised in The Netherlands. I live on Planet Earth on a spot of land called Canada. We have noisy neighbours. - harvested from Usenet
From: baron on 25 Nov 2009 05:01
Sylvia Else Inscribed thus: > Baron wrote: >>> Removing the return leg isn't going to cause problems in a properly >>> wired US home. Don't know about the UK. >> >> The lights would go out ! Domestic properties usually have just a >> 240v >> single phase feed. Usually you would get a single phase running down >> one side of the street and another phase running down the other. >> > > I said I have two phases. > > Sylvia. Yes I know ! I answered the question above ! -- Best Regards: Baron. |