Not that i'm allowed to touch my home electrics anymore, (Part P, grr)
but say I had a mystery wire dangling near my fusebox, which disappears
into the 1st floor landing void. How could I identify this wire without
energising it (as i'm not at all sure what is connected to the other
end) I have a sneaky feeling it goes to the loft, but have no way of so
determining.

The other wires all go to a CU with MCB's, so isolation of all the
other wiring is not a problem.

How do the experts identify individual wires once they've gone through
floor voids etc .. ?

I'm sure there's a simple explanation staring me in the face here !!

Cheers

Paul.

wrote:

Not that i'm allowed to touch my home electrics anymore, (Part P, grr)
but say I had a mystery wire dangling near my fusebox, which disappears
into the 1st floor landing void. How could I identify this wire without
energising it (as i'm not at all sure what is connected to the other
end) I have a sneaky feeling it goes to the loft, but have no way of so
determining.

The other wires all go to a CU with MCB's, so isolation of all the
other wiring is not a problem.

How do the experts identify individual wires once they've gone through
floor voids etc .. ?

Duno about experts,but I short the end of them and see which is shorted
at the other end.

I once had to rewire a disco that was full of lights all wired using
different bcables into an old biscuit tin.

My soluition was to hacsa the lot off, set up proper box, and apply
mains voltage to any pairt that seemed to have a load on them.

This way I documented them all, watching whichj lights came on.

The last as two 4 way cables that all seemed interconneceted. I
eventually traced these to a bank of 7 lights that used one red cable as
a common return.





I'm sure there's a simple explanation staring me in the face here !!

Nort really. You can put an audio signal on them and go looking with a
sensitive audio detecor.

If it goes nowhere that you can find and end of (I have one like that
here) cut it and bury out out of sight.


Cheers

Paul.

wrote:

The other wires all go to a CU with MCB's, so isolation of all the
other wiring is not a problem.

How do the experts identify individual wires once they've gone through
floor voids etc .. ?

One way is with expensive wire tracing generators and signal detectors
(the sort of kit BT use for tracing wires underground etc).

I'm sure there's a simple explanation staring me in the face here !!

A few things you could do...

Bare then ends of the wire you can see and measure the resistance
between each of the cores. If you get infinite resistance measured
between each with you DMM on its highest range, then it ought to be safe
to power the wire up temporarily. You could turn off all the other
circuits and connect this one to power (via a low value MCB) in the CU.
Then use a voltage/metal detector to check each likely wire you think it
might be to see if it is live.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Fri, 11 Feb 2005 12:34:56 +0000, John Rumm wrote:

A few things you could do...

Bare then ends of the wire you can see and measure the resistance between
each of the cores. If you get infinite resistance measured between each
with you DMM on its highest range, then it ought to be safe to power the
wire up temporarily. You could turn off all the other circuits and connect
this one to power (via a low value MCB) in the CU. Then use a
voltage/metal detector to check each likely wire you think it might be to
see if it is live.

If you're going to do that, I would be inclined to supply the live via a
2 Megohm 400V min (not 240V, mains peaks at upto 350V) rated 1/4W
min resistor. That will limit the fault current to 1/8mA. Assuming the
insulation resistance is =2Megohms (big assumption for old random cable)
then you should get a reasonable electric field for the detector to pick
up.

You could progress through smaller resistors, but I wouldn't go below
0.5Megohm.

I didn't say that would be a 100% safe thing to do, but it would be safer
than whopping unlimited mains on an unknown cable. Only you're bound to
find the random cable end floating around and touching something metal, or
you'll stick your fingers on it when fishing around in the dim attic.

A low value MCB will still kill you and an RCD will still give a hefty
bang on a dead short.

You can get (beg/borrow/steal) cable tracers (try a
network installer or a phone installer) - these are a tad safer.

HTH

Tim

Tim S wrote:

If you're going to do that, I would be inclined to supply the live via a
2 Megohm 400V min (not 240V, mains peaks at upto 350V) rated 1/4W
min resistor. That will limit the fault current to 1/8mA. Assuming the
insulation resistance is =2Megohms (big assumption for old random cable)
then you should get a reasonable electric field for the detector to pick
up.

Good advice. Partly why I was suggesting a non contact method for
detection, but thinking through the possible scenarios that is only safe
when you can pretty much guarentee non contact! If in doubt, wear
insulating gloves and make sure there is no one likely to be a liability
in the house.

You can get (beg/borrow/steal) cable tracers (try a
network installer or a phone installer) - these are a tad safer.

Probably the best way... not looked lately, but it may be a small set is
not as expensive as it once was.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article .com,
" says...
Not that i'm allowed to touch my home electrics anymore, (Part P, grr)
but say I had a mystery wire dangling near my fusebox, which disappears
into the 1st floor landing void. How could I identify this wire without
energising it (as i'm not at all sure what is connected to the other
end) I have a sneaky feeling it goes to the loft, but have no way of so
determining.

The other wires all go to a CU with MCB's, so isolation of all the
other wiring is not a problem.

How do the experts identify individual wires once they've gone through
floor voids etc .. ?

I'm sure there's a simple explanation staring me in the face here !!

When you say wire do you mean a cable containing two or more
conductors, or a single conductor? If it's a single conductor and an
old house then it could be an aerial.

wrote:

I'm sure there's a simple explanation staring me in the face here !!

Why not shove 12 volts up it rather than mains.
12V DC would be easier to spot than randon 230v

Could it not be an old disused immersion heater feed(following a
combi-boiler installation sometime in the distant past)?

--
http://gymratz.co.uk - Best Gym Equipment & Bodybuilding Supplements UK.
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http://fitness-equipment-uk.com - UK's No.1 Fitness Equipment Suppliers.
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In article .com,
wrote:
Not that i'm allowed to touch my home electrics anymore, (Part P, grr)
but say I had a mystery wire dangling near my fusebox, which disappears
into the 1st floor landing void. How could I identify this wire without
energising it (as i'm not at all sure what is connected to the other
end) I have a sneaky feeling it goes to the loft, but have no way of so
determining.

Best to think it's faulty in some way and remove it.

The other wires all go to a CU with MCB's, so isolation of all the
other wiring is not a problem.

How do the experts identify individual wires once they've gone through
floor voids etc .. ?

Old houses will often have odd ends of old wiring around. Hack it off if
it bothers you, but don't even think of using it.

I'm sure there's a simple explanation staring me in the face here !!

There are ways of tracing cable runs, but not of much use in this case.

--
*The most wasted day of all is one in which we have not laughed.*

Dave Plowman London SW
To e-mail, change noise into sound.

wrote in message
oups.com...
Not that i'm allowed to touch my home electrics anymore, (Part P, grr)

You ARE allowed to touch them. (apart from the kitchen but I think this
will disappear soon like the pressurised HW systems restriction)

On Fri, 11 Feb 2005 13:43:28 +0000, John Rumm
strung together this:

You can get (beg/borrow/steal) cable tracers (try a
network installer or a phone installer) - these are a tad safer.

Yep, that'd be my choice.

Probably the best way... not looked lately, but it may be a small set is
not as expensive as it once was.

About £35 from http://www.millsltd.co.uk IIRC.
--

SJW
Please reply to group or use 'usenet' in email subject

Rob Morley wrote:
zymurgy says...
Not that i'm allowed to touch my home electrics anymore, (Part P,
grr)
but say I had a mystery wire dangling near my fusebox,
How could I identify this wire without energising it

When you say wire do you mean a cable containing two or more
conductors, or a single conductor? If it's a single conductor and an

old house then it could be an aerial.

LOL!

Actually I do have Electrical Installation C&G parts 1 & 2 from way
back when, so I can identify a relatively new T+E when I see it ;-)

Just a bit rusty on cable tracing, but certainly appreciate all of the
answers i've had to stimulate the dormant brain cells.

Cheers,

Paul.

Lurch wrote:
John Rumm strung together

You can get (beg/borrow/steal)

may be a small set is not as expensive as it once was

About =A335 from http://www.millsltd.co.uk IIRC.

Couldn't see much below =A343 .. ?

Cheers

Paul.

On 14 Feb 2005 10:36:35 -0800, strung
together this:

About £35 from http://www.millsltd.co.uk IIRC.

Couldn't see much below £43 .. ?

Ah, I didn't remember correctly then, looking at the catalogue now it
would appear I meant £45, not £35. Sorry.
--

SJW
Please reply to group or use 'usenet' in email subject