This afternoon I turned off a switched fused spur supplying a 3kw water
heater and got a packet off the switch.
This is an MK dpdt thing with non-metallic front and pattress. Plastic for
want of a better word. Supply is from a 16A mcb via a 60A rccb.
All items and and cabling are new within the last 2 months.
All are located within an unheated outdoor, but waterproof, building.
Condensation may be a problem but there was no sign of any water in, on or
around the offending spur. I put a tester to the plastic casing and it
showed mains voltage over most of the surface.
Any ideas why I copped a packet and also why the rccb didn't trip?
Many thanks
Sunbeam

All are located within an unheated outdoor, but waterproof, building.

What earthing system is used for this outbuilding? Perhaps the house earth
has been inappropriately exported, or there isn't an earth at all.

If there is any distance from the house, the building should have a local TT
earthing system with earth rod.

In any case, perform an earth loop impedence test and ensure it is
reasonably low.

Christian.

"Sunbeam" wrote in message
...

"Dave Plowman (News)" wrote in message
...
In article ,
Sunbeam wrote:
This afternoon I turned off a switched fused spur supplying a 3kw
water
heater and got a packet off the switch. This is an MK dpdt thing with
non-metallic front and pattress. Plastic for want of a better word.
Supply is from a 16A mcb via a 60A rccb. All items and and cabling are
new within the last 2 months. All are located within an unheated
outdoor, but waterproof, building. Condensation may be a problem but
there was no sign of any water in, on or around the offending spur. I
put a tester to the plastic casing and it showed mains voltage over
most
of the surface.

The obvious answer is that it's been coated with something conductive.

That would seem most odd. This is a brand new fitting from a well known &
hopefully reputable manufacturer. It has been installed straight from the
box, correctly and with no modifications. The fitting has definitely not
been coated in any way other than by the manufacturer or the atmosphere.


Moisture on its own won't make plastic live.
Perhaps so, but it is the only reasonable alternative that I can think of
at present.
--
*I don't suffer from insanity; I enjoy every minute of it.
A feeling that I also enjoy.

Sunbeam.


Replace the isolation switch with another one and see if the problem
persists; sounds
like a funny one so faultfinding by substitution is a good place to start.
Post back if you do it and let us know whether it has any effect.

Andy.

In article ,
Sunbeam wrote:

This is an MK dpdt thing with non-metallic front and pattress.

Any chance that a live wire is being touched by
a front panel fixing screw?

--
Tony Williams.

In article ,
Sunbeam wrote:
This afternoon I turned off a switched fused spur supplying a 3kw water
heater and got a packet off the switch. This is an MK dpdt thing with
non-metallic front and pattress. Plastic for want of a better word.
Supply is from a 16A mcb via a 60A rccb. All items and and cabling are
new within the last 2 months. All are located within an unheated
outdoor, but waterproof, building. Condensation may be a problem but
there was no sign of any water in, on or around the offending spur. I
put a tester to the plastic casing and it showed mains voltage over most
of the surface.

The obvious answer is that it's been coated with something conductive.
Moisture on its own won't make plastic live.

--
*I don't suffer from insanity; I enjoy every minute of it.

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

"Christian McArdle" wrote in message
et...
All are located within an unheated outdoor, but waterproof, building.

What earthing system is used for this outbuilding? Perhaps the house
earth
has been inappropriately exported, or there isn't an earth at all.

If there is any distance from the house, the building should have a local
TT
earthing system with earth rod.

In any case, perform an earth loop impedence test and ensure it is
reasonably low.

Christian.


Thanks Christian,

the earth is good. New 50m run of 10mm2 SWR to the junction box which is
0.5m from the incoming (electricity company) 3 ph meter. Tested when
installed a couple of months back
Whether the earth be good or otherwise, why did I cop a packet from a
totally plastic encased switched fused spur?

Sunbeam.

"Tony Williams" wrote in message
...
In article ,
Sunbeam wrote:

This is an MK dpdt thing with non-metallic front and pattress.

Any chance that a live wire is being touched by
a front panel fixing screw?

--
Tony Williams.

Thanks Tony,

that was the 1st thing I checked. The screws are not live but the rocker
switch and an area extending approx.12mm around it are showing full
voltage.
Have checked the connections within and they are all faultless.

Sunbeam.

"Dave Plowman (News)" wrote in message
...
In article ,
Sunbeam wrote:
This afternoon I turned off a switched fused spur supplying a 3kw water
heater and got a packet off the switch. This is an MK dpdt thing with
non-metallic front and pattress. Plastic for want of a better word.
Supply is from a 16A mcb via a 60A rccb. All items and and cabling are
new within the last 2 months. All are located within an unheated
outdoor, but waterproof, building. Condensation may be a problem but
there was no sign of any water in, on or around the offending spur. I
put a tester to the plastic casing and it showed mains voltage over
most
of the surface.

The obvious answer is that it's been coated with something conductive.

That would seem most odd. This is a brand new fitting from a well known &
hopefully reputable manufacturer. It has been installed straight from the
box, correctly and with no modifications. The fitting has definitely not
been coated in any way other than by the manufacturer or the atmosphere.


Moisture on its own won't make plastic live.
Perhaps so, but it is the only reasonable alternative that I can think of
at present.
--
*I don't suffer from insanity; I enjoy every minute of it.
A feeling that I also enjoy.

Sunbeam.

On Mon, 08 Nov 2004 12:33:22 +0000, Tony Williams wrote:

In article ,
Sunbeam wrote:

This is an MK dpdt thing with non-metallic front and pattress.

Any chance that a live wire is being touched by
a front panel fixing screw?

This would imply not only the falt you describe but also that the earthing
is suspect since the screws are earthed via inset washers in the fitting.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

In article ,
Sunbeam wrote:

that was the 1st thing I checked. The screws are not live but the
rocker switch and an area extending approx.12mm around it are
showing full voltage.

It is as though the metal bracket the rocker switch
pivots on has a voltage on it. A bit of surface dust
and condensation providing a conductive path to the
outside. Sounds like an iffy switch.

Perhaps this is a situation where you might consider
a high current pull switch instead, for future safety.

--
Tony Williams.

the earth is good. New 50m run of 10mm2 SWR to the junction box which is
0.5m from the incoming (electricity company) 3 ph meter. Tested when
installed a couple of months back

50m from the house with an exported earth rings a few alarm bells, although
I doubt you'd ever get enough potential difference between it and local
earth to cause a shock, unless your house is built in a "difficult"
location, such as on a granite clifftop.

Christian.

That would seem most odd. This is a brand new fitting from a well known &
hopefully reputable manufacturer.

Have you heard of the bathtub reliability curve? Always suspect new
components before ones that have been proven by a few year's service.

Christian.

Christian McArdle wrote:
That would seem most odd. This is a brand new fitting from a well known &
hopefully reputable manufacturer.


Have you heard of the bathtub reliability curve? Always suspect new
components before ones that have been proven by a few year's service.

Very true. I've had failures on brand-new bathtubs, but ones that've
been in for a while generally seem to keep on going. :-)

Very true. I've had failures on brand-new bathtubs, but ones that've
been in for a while generally seem to keep on going. :-)

But after 10 years or so, they do rust away at an increased rate.

Christian.

Very true. I've had failures on brand-new bathtubs, but ones that've
been in for a while generally seem to keep on going. :-)

But after 10 years or so, they do rust away at an increased rate.

P.S. Was it a bathtub that you were replacing in Talfourd Avenue yesterday?

Christian.

"Sunbeam" wrote in message ...
This is an MK dpdt thing with non-metallic front and pattress. Plastic for
want of a better word.

It sounds like something that the manufacturers need to be advised of.
There are counterfeit products around. Keep hold of the evidence
though. Replace it asap.

On Sun, 7 Nov 2004 23:23:28 -0000, "Sunbeam"
wrote:

This afternoon I turned off a switched fused spur supplying a 3kw water
heater and got a packet off the switch.
This is an MK dpdt thing with non-metallic front and pattress. Plastic for
want of a better word. Supply is from a 16A mcb via a 60A rccb.
All items and and cabling are new within the last 2 months.
All are located within an unheated outdoor, but waterproof, building.
Condensation may be a problem but there was no sign of any water in, on or
around the offending spur. I put a tester to the plastic casing and it
showed mains voltage over most of the surface.
Any ideas why I copped a packet and also why the rccb didn't trip?
Many thanks
Sunbeam


Hi,

Sounds like the there is a fault with the earthing of the switch. Is
there a plate behind the front which earths the two screw holes? If
this is floating it could allow some capacitative coupling or tracking
(through damp) of mains voltages.

If connected and there is a break in the earthing elsewhere then
capacitative coupling from live could allow it to float at a high
voltage, especially if the wiring is old.

If all the earthing of the switch and its supply is in order, it could
be defective plastic that can absorb water through being porous. Try a
different make switch so to be sure it is not from the same batch as
the original.

cheers,
Pete.

Aidan wrote:
"Sunbeam" wrote in message
...
This is an MK dpdt thing with non-metallic front and pattress.
Plastic for
want of a better word.

It sounds like something that the manufacturers need to be advised
of.
There are counterfeit products around. Keep hold of the evidence
though. Replace it asap.
Well I'm curious as to what the "voltage" has been measured with. Not
one of those lightstick things by anychance, that show a voltage if
you scratch your arse the wrong way? I know he had a shock, but damp
hands damp fitting might havr caused that, or static discharge to the
metal screws.
--
Richard

Christian McArdle wrote:
Very true. I've had failures on brand-new bathtubs, but ones that've
been in for a while generally seem to keep on going. :-)

But after 10 years or so, they do rust away at an increased rate.


P.S. Was it a bathtub that you were replacing in Talfourd Avenue yesterday?

Nope - that's about the one thing that's still OK in that house :-)

Gas valve on ancient floor-standing boiler packed up on Friday, No
immersion heater either ... brrr!