Yup, if you have a static IP then it ought to work anywhere - the phone
is told to go to a news server running on *your* PC. From there is gets
redirected to the one available to virgin BB customers.
Without a static IP, then you can still get round it if your router can
use dyndns - that way it maintains a name to IP mapping, and the phone
can still visit a static "name" which will resolve into your varying IP.
here is that far up the stream, as the mains Earthing in the house has been in
situ since I moved here, some 14 years ago and has been tested in anger IIRC at
various times with short circuits and fuses blowing but I get that you're
covering the bases and going to the worst case scenario, identifying the source.
I'd check the earth wiring from the suspect sockets back to the Consumer
Unit earth bar.
If that had become disconnected, then any normal mains filters in the
appliances that generate small leakage would cause the socket / cabinet
non-earth to float to about 120v, but at high impedance, giving the
tingle you describe.
OK, let us know how it goes... (any spare wire will do - so long as you
measure its resistance and take that away from your result)
For in depth theory, see:
A common design of input filter will have a couple of inductors inline
with the L&N to act as chokes (inductors chosen such that they conduct
very well at mains frequencies, and very poorly at radio frequency), and
then usually a pair of capacitors connected between L & E and E & N.
(and / or possibly one between L & N as well)
See the pic on the front of the filter shown here:
Capacitors are like inductors in that their "resistance" (or reactance
as its called when dealing with AC) varies with frequency. However their
response is the reverse of an inductor - i.e. they totally block DC, and
conduct increasingly well with rising frequency. So if you pick a very
low value of capacitor and slap it across the mains to earth, it has
almost no effect at mains frequency, but HF noise will be coupled to
earth via the cap.
Say you take a suppression cap with a capacitance of 2200pF. The
reactance will be given by the formula
Xc = 1 / 2 x pi x f x c
So at 100kHz the cap will look like 1 / 2 x pi x 100000 x 100 x 10^-9 approx 636 ohms. Hence it conducts and snubs the radio frequency quite
well. However at 50Hz mains you get and effective resistance of 1.3M ohms.
So if you were to redraw your effective circuit you have your earth wire
connected to L & N via a pair of 1.3M Ohm resistors. Since both
"resistors" are the same size, if the earth is not connected to anything
at all, it will just sit half way between the L & N voltage - or
typically about 120V. However even in this circumstance the current that
can flow to earth is tiny, if you do V = IR you get 230 / 1.3M = 0.18mA.
So lets say your earth is not as good as it ought to be, you come along
and stick your mit on the earthed tap, and the cabinet which is
connected to the centre point of this notional resistor network, and you
will get some voltage across you that you can feel. The maximum current
that can flow through you is limited less than 200uA though.
The physics is actually quite easy to visualise if you think about it
from the basic principles.
A capacitor is basically a pair of conductive "plates" separated by an
insulator. When you apply a voltage across the plates, you see a some
current flow briefly into it as it "charges up" (in reality you are
storing a small amount of electrical energy in an electric field created
by the plates - all the free electrons migrate round to one of the
plates - leaving it negatively charged). You may remember physics demos
with a gold leaf electroscope which shows how you can accumulate charge
on a plate?
Hence with a DC supply connected to a cap, you get a brief flow of
current as it charges, and then the current flow falls away to nothing.
Since current can't pass across the insulating gap. If however you now
swap the polarity of the battery, then you will again see a brief flow
of current as you discharge it and the recharge it with the opposite
A cap across an AC supply thus looks like it actually conducts because
the continual reversal of polarity of the supply allows it to keep
passing current as it is charged, discharged and recharged in the
opposite direction. How well it conducts is a function of how quickly
you reverse the supply polarity (i.e. the frequency of the AC), and the
size of the capacitor.
The larger the capacitor, or the higher the frequency, the better the
conductance (or lower the resistance).
There are basically two common cases where this is going to be relevant
in mains electrics. The first you have experienced first hand -
capacitors in input filters will leak small amounts to earth. So in your
case with no earth, you see bits of metal feeling live to the touch.
Alternatively you can start to eat into the leakage allowed by a RCD and
get an unexpected trip if you have too many of these things on one RCD.
The second one is with capacitive coupling, where you don't even have an
identifiable capacitor as such. Long lengths of wire laying side by side
will exhibit a tiny capacitance as well. If one of these is live and the
other not connected to anything "solid" like L or N or E, then it will
tend to appear to be live as well. This can fool some sensitive digital
meters, or cause CFL bulbs to flash unexpectedly in the dark, or
sometimes even give a tingle sensation similar to what you were
Unplugged from utility cupboard = no tingle!
Plugged into different outlet on other side of cupboard = no tingle!
or wall outlet where first plugged in???
or close proximity of dryer to cabinet???
Aaaah, it's like a dangerous version of pin the tail on the donkey!
Even a poor earth should suppress any tingles due to capacitive leakage.
That's not to say that a poor earth is in any way acceptable though.
If the tingles remain I'd suggest checking earth continuity from the
cabinet all the way back to the main earth terminal - use a multimeter
and long flying lead if you haven't got a loop tester.
Deano, earlier wrote:
This is a 3-core flex, I presume? That's a rather basic question, but I
don't think anyone else has asked...
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