Two phases to house - loss of neutral
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From: Trevor Wilson on 23 Nov 2009 22:20 Phil Allison wrote: > "Trevor Wilson" > >> >> **AFAIK, the US system is fundamentally different to ours. > > > ** In the US and Canada - it is NOT permitted to link neutral > and earth or plumbing within a premises. > > See here under the heading "Regulations". > > http://en.wikipedia.org/wiki/Earthing_system > > The MEN system used here in Australia seems to be unique. > > See last para on same page. **Interesting. I'd have thunk that some places in Europe might employ a similar system. Guess not. Ever since I ran across my first US audio product with a high value resistor to chassis from (allegedly) Neutral, I realised that the US system was highly flawed. -- Trevor Wilson www.rageaudio.com.au
From: Bob AZ on 23 Nov 2009 22:24 > My electrician says it's not an issue, but I can't see why. > > Any thoughts? > > Sylvia. Sylvia Thought one. Get rid of the electrician. In my experience with loss of neutrals it is the number one cause of electrical equipment/lighting failure. Bob AZ
From: D Yuniskis on 23 Nov 2009 22:43 Phil Allison wrote: > "Trevor Wilson" > >> **AFAIK, the US system is fundamentally different to ours. > > ** 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). So, you can encounter all sorts of different situations here in the US (I've even worked on homes with knob & tube wiring!) > See here under the heading "Regulations". > > http://en.wikipedia.org/wiki/Earthing_system > > The MEN system used here in Australia seems to be unique. > > See last para on same page.
From: F Murtz on 23 Nov 2009 22:46 Sylvia Else 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. not a neutral problem but. I can remember an old lady complaining that every time she turned the hot water tap the lights came on half brilliance.and sure enough they did. she had three phase and an instantaneous three phase water heater. one phase had gone and the heater caused the dead phase to be live in series with element.(the water flow closes the heater circuit)
From: nesesu on 23 Nov 2009 23:07
On Nov 23, 6:36 pm, "Phil Allison" <phi...(a)tpg.com.au> wrote: > "Trevor Wilson" > > > > > **AFAIK, the US system is fundamentally different to ours. > > ** In the US and Canada - it is NOT permitted to link neutral and earth > or plumbing within a premises. > > See here under the heading "Regulations". > > http://en.wikipedia.org/wiki/Earthing_system > > The MEN system used here in Australia seems to be unique. > > See last para on same page. > > ..... Phil Rubbish. In most of Canada, it is manditory that the neutral be bonded to earth at only ONE point, the service entrance switch enclosure. From that point an earth conductor is connected to 2 ground rods and to any metallic piping system(s). Neutral failure is a not uncommon problem especially with overhead aluminum 'triplex' service drops. A seagull deficates on the bare aluminum neutral and it soon rots off leaving an open neutral condition. Ground rod to earth resistances of 5 ohms are not uncommon, so a 10A unbalance between 'phases' could give a 50V offset of the neutral. Neil S. |