Was at a mates and he has an outdoor ornamental lamp post, when it is
switched on the bulb lights for a few seconds and then goes out by
tripping the RDC at the main board. We checked the lightbulb socket
that looks ok, we checked the socket where the feed comes from (no loose
wires) and thats ok. We checked most of the armoured cable and that
looks intact a few feet of the cable is under concrete so left that for
the moment, the cable is buried mainly in a gravel drive. When the
lightbulb is removed it still trips the RDC. The lamp is fed off the
ground floor socket ring.
What would be the way forward for identifying the problem, he will have
a multi meter next week.
Do you have armoured cable going into a plug?
I would work back from the lamp, isolating each piece of cable, and see
if it tripped the RCD. I presume you have a wet junction box somewhere.
You do mean RCD and not MCB?
Socket? Socket ring?
What size cable?
Armoured cable to a 13A plug perhaps?
I know of no armoured cable that I could correctly terminate in a 13A
Any armoured cable I have used would clearly indicate where an earth
leakage problem was lurking, without the aid of a meter.
Concrete should be o/k, but gravel with a vehicle or two will make a
mess of the sheath.
On 30/08/2015 17:50, Archibald Tarquin Blenkinsopp wrote:
The armoured cable is wired directly in to a fused juction box with
switch, I say fused junction box but its like a plug socket without the
square holes for a plug (dont know the correct name) the socket is
mounted exactly where the armoured cable enters the house.
the cable in the driveway we have checked and it looks intact with no
damage, the length of cable that is outdoors appears to be one piece.
the cable from memory maybe 1.5 to 2 cms in diameter.
Where the cable is covered in the drive is at the edge and unlikely to
have caused damage and certainly there is no obvious visual damage.
Do you mean something like this?
What happens at the other end of the armoured cable. Does it go directly
to the light fitting?
Yes thats the type of box.
Where the cable leaves the driveway and to the base of the lampost is
concrete so at this stage trying not to have to dig that up. We thought
maybe a juction box at the base of the cable but the sections are not
easy to disassemble.
Do you mean the RCD trips or is it an MCB that trips?
If it is an RCD can't think of a mechanism that would take a few seconds
to trip. It should be instantaneous or not trip at all.
I did have a length of T&E that had got water in it and that would trip
an MCB after a delay. I presumed that the water became ionised by the
voltage and draw more current and so on until the MCB tripped. I did not
bother to investigate but just replaced the cable.
If you disconnect everything at the lamp end to leave three bare wires
in fresh air and the RCD or MCB trips then it is damaged cable and
should be replaced.
If you can find the damaged area, a repair might be possible by drying
it out and resealing with a water proof joint but it could still be a
These days the bulb could be replaced with a solar powered charger with
a battery and a LED lamp?
Pretty obvious that water has encroached into the cable due to the outer
being breached. New cable run needed I'd suggest, to attempt to splice in
a new piece where the leak is opens it up to the connections being a weak
link and it all happening again. Did he not use d some form of ducting for
From the Sofa of Brian Gaff Reply address is active
"ss" < email@example.com> wrote in message
It would appear the original owners of the house never used any ducting,
the cable is 6 inches down under gravel drive, although so far what has
been exposed appears to be ok. The cable is on the edge of the drive so
really should not have got damaged with traffic.
He wants to check any other possibilities before digging the concrete up.
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