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'[OT] Burning the hot side of the plug'
1998\07\26@140307 by wft

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I have not yet seen an explanation that is believeable.

Possibly the fact that the hot side is at higher potential with respect
to air/environment (which I assume is near ground) causes a long term
chemical reaction that raises the resistance of the hot side.

Gus
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1998\07\26@210207 by Paul B. Webster VK2BZC

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Gus Calabrese <EraseMEwftspam_OUTspamTakeThisOuTMAIL.FRII.COM> wrote:

> I have not yet seen an explanation that is believeable.

 Oh dear!  Was my explanation not believeable?  Shall I try and
re-state it stepwise?

1) The problem occurs mostly on outlets used for medium to high current
loads.

2) By implication, it is caused by current in the circuit, not voltage
across the adjacent pins.

3) Current causes *heating* in the contacts.  The contacts are
constructed from phosphor-bronze or similar material, tempered by the
stamping process used to fabricate them.

4) Heating above a certain temperature causes annealing so that the
contacts soften and the contact force decreases, raising the contact
resistance.  Heating of the chlorocarbon plastics used in plugs causes
release of monomer and to some extent, free chloride which corrodes even
corrosion-resistant alloys.

5) Loss of contact by these mechanisms causes further IÓR heating so
this is a non-linear (compounding) effect.

6) The live and neutral contacts in the socket are *different* as the
live goes to the switch contact whilst the neutral goes to a screw
terminal where it is anchored to the incoming cable and in the case of
double outlets, to the opposite outlet assembly.  Consequently, the live
contact is less firmly anchored and more likely to have poor contact in
the first place.

7) A most significant corollary: The live contact is not heat-sunk by
attachment to a larger area of metal including the incoming cable.
Further, it is subject to aditional contact heating from any poor
contact in the switch mechanism.

 In summary, it is little surprise that the live contact overheats by
preference, *on a switched outlet*.  I doubt you will observe the
phenomenon on an unswitched outlet except *of course* where this is used
with a previously damaged plug.

 Cheers,
       Paul B.

1998\07\27@133618 by Peter L. Peres

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On Mon, 27 Jul 1998, Paul B. Webster VK2BZC wrote:

- snip -
>   In summary, it is little surprise that the live contact overheats by
> preference, *on a switched outlet*.  I doubt you will observe the
> phenomenon on an unswitched outlet except *of course* where this is used
> with a previously damaged plug.

So sorry to burst your bubble, but I was talking about our plugs (which I
have drawn before) and Euro amd Schukos. These are all symmetrical, there
is no physical difference between the attachments. The effect exists, but
I have no statistical data to confirm it... and I never implied anything
but brand new plugs used normally for a few years.

Peter

1998\07\28@045023 by g.daniel.invent.design

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Peter, Paul

For some sockets the contacting "fingers" are designed for access by
plug pins of less thickness than that of a common electrical test
meter's probe's diameter. An electrician will statistically test Phase
(live 110/220 AC etc) more often than the Nutral connection. (Earth also
tested)

This is a potential cause for stressing of Phase connection more than
Nutral.

In addition, Peter's should perhaps reread Paul's one significant
point(No.7) which explained that the switched PHASE connection *ON THE
SOCKET* has a greater cooling volume due to the thick copper track
leading to the switch.

Regards,
Graham Daniel
(Electrician day job but counting down)

Peter L. Peres wrote:
{Quote hidden}

1998\07\28@051516 by tjaart

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G.Daniel Invent Design wrote:

> Peter, Paul
>
> For some sockets the contacting "fingers" are designed for access by
> plug pins of less thickness than that of a common electrical test
> meter's probe's diameter. An electrician will statistically test Phase
> (live 110/220 AC etc) more often than the Nutral connection. (Earth also
> tested)
>
> This is a potential cause for stressing of Phase connection more than
> Nutral.
>
> In addition, Peter's should perhaps reread Paul's one significant
> point(No.7) which explained that the switched PHASE connection *ON THE
> SOCKET* has a greater cooling volume due to the thick copper track
> leading to the switch.

I had a look, and the length of wire connecting the sockets are
such that any cooling effect of a switch can be ruled out. The
wire guages are identical. The pins on the plug are also identical.

--
Friendly Regards

Tjaart van der Walt
tjaartspamspam_OUTwasp.co.za

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1998\07\28@052800 by paulb

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Grrr!

 Tjaart van der Walt and G.Daniel Invent Design wrote referring to a
"cooling" effect of the switch on the live pole.  That's *not* what I
said!

 I suggested that the connection to the switch, being a *smaller* piece
of metal, *not* connected to the incoming cables from the wall, and the
possibility of poor contact in the switch mechanism being an additional
source of heat, means that this (live) contact is *poorly* heat-sunk and
therefore runs *hotter*; not surprisingly; overheating.

 Is that clear?
--
 Cheers,
       Paul B.

1998\07\28@091358 by Andy Kunz

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This whole thing about which lead wears quicker might bear some
relationship to brushed motors, where one pole consistenly wears more than
the other (the + side).

Perhaps somebody might like to investigate that avenue.

Andy

==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
==================================================================

1998\07\28@095953 by Morgan Olsson

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>  I suggested that the connection to the switch, being a *smaller* piece
>of metal, *not* connected to the incoming cables from the wall, and the
>possibility of poor contact in the switch mechanism being an additional
>source of heat, means that this (live) contact is *poorly* heat-sunk and
>therefore runs *hotter*; not surprisingly; overheating.
>
>  Is that clear?

Yep.

I just wonder: Is this a manually operated switch,
or operated by the plug?

For safety?

/Morgan

>  Cheers,
>        Paul B.
>
>
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  KILLspammrtKILLspamspaminame.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\07\28@100659 by tjaart

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Andy Kunz wrote:

> This whole thing about which lead wears quicker might bear some
> relationship to brushed motors, where one pole consistenly wears more than
> the other (the + side).
>
> Perhaps somebody might like to investigate that avenue.

It is AC.

--
Friendly Regards

Tjaart van der Walt
RemoveMEtjaartTakeThisOuTspamwasp.co.za

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1998\07\29@110923 by Peter L. Peres

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On Tue, 28 Jul 1998, Andy Kunz wrote:

> This whole thing about which lead wears quicker might bear some
> relationship to brushed motors, where one pole consistenly wears more than
> the other (the + side).

That one is easy. The constant arcing transports electrons in one
direction and ions in the other through plasma hot enough to melt the
electrodes locally. At equal electrode temperature, the material with
lower valence per volume unit should electromigrate more, per volume unit
(Cu = 1 and dense, C = 4, but far less dense). This neglects mechanical
side effects and the *side* of a given arc that gets hotter, plus thermal
conductivity.

Now, if you add all this up, you have a soft bronze carbon electrode that
is the '+' pole in an electric arc, facing a bronze armature that is
moving very fast, so any debris extracted from the carbon do not adhere to
the moving armature, which conducts heat better, and stays colder on
account of its larger mass...

hope this helps ;)

       Peter

PS: Was this short enough ?

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