[sdiy] Neutral ground

[Magnus Danielson]

From: Woody Wall <woody.wall at gmail.com>
Subject: [sdiy] Neutral ground [was: midi optocouplers]
Date: Mon, 12 Dec 2005 15:49:31 -0600
Message-ID: <8077cdfd0512121349s72895bc7j7ea871cd3a3eb45f at mail.gmail.com>

Woody,

> So does this mean that neutral and earth ground are the same? Or am I missing
> something? It's been a long time since I studied this in school.

There is an important difference. The Neutral is what you hook your load to,
so it sits between the Line (or Phase as we say here in Europe) and Neutral
(or Zero as we say here ... ya know where). The Earth or Protective Ground is
hooked to the chassi of the apparatus, so if the phase (or one of the phases
in a three-phase device) gets loose, shorts to the chassi or whatever, it hits
the protective ground. Even more importantly, if the Zero gets loose in such a
case, the whole chassi would be at the phase voltage and you can get zapped
arm-to-arm and cardiac failure may follow as a result. The Protective Ground
should never run any serious current, it usually only has some minor leakage
current from the line-filter.

In the fuse-box is the Zero and Protective ground connected at a central point,
but from that point on they are separated. A ground-breaker fuse will sense the
current in the protective ground and cut the phase(s) for that circuit in
(hope) of removing the hazard. You should use one when working with tools in
the garden. It is a cheap life-insurance.

A good rule of thumb is that when a cable is being pulled out of its socket or
other installation, the last wire to loose contact shall be the protective
ground.

When thinking about it, it is quite some time that I learned this in school
too, but this is certainly one of the things which I recall. I *care* about
safety, but I am not manical about it either, but a rational reasoning and
knowing why not to cut corners even if the brain tells you it is safe is really
the mandatory mode of operandi for these issues.

Cheers,
Magnus - was grounded to protective ground today

> Woody
> 
> On 12/12/05, harrybissell <harrybissell at prodigy.net> wrote:
> 
>     USA uses 120VAC...
>    
>     Hot will have 120V AC with respect to earth ground
>    
>     Neutral should have no voltage with respect to earth ground.
>    
>     They can get reversed sometimes... with disasterous results in
>     an audio system.  Having one chassis at 'hot' and another at
>     neutral can mean line voltage in an audio cable...
>    
>     H^) harry
>    
>     Karl Ekdahl wrote:
>    
>     > I'd really like to know what the "hot"/"neutral" is all about, here in
>     > sweden we've got no such thing but i'm moving to the US in a week so
>     > i'd better learn....
>     >
>     > Karl
>     >
>     > Samppa Tolvanen <samppa.tolvanen at gmail.com> skrev:
>     >
>     >       We Finns are enjoying 230VAC with non-polarized mains
>     >      sockets.
>     >
>     >      Shouldn't We all agree the truth, there's NO neutral wire.
>     >      Just for newbies?
>     >
>     >      Grant said:
>     >      "It is a good idea to verify that your electronic music
>     >      studio wall
>     >      sockets are wired correctly.
>     >      I have seen strange things happen when neutral and hot are
>     >      reversed.
>     >      Even on transformer isolated equipment."
>     >
>     >      This sounds like badly designed equipment.
>     >
>     >      Samppa
>     >
>     >
>