Shock off plastic light switch.

[RonnyRaygun]

How is this possible?

My mum has a double two way switch that operates the kitchen and dining room lights. I won't touch that switch any more because when I do I get a shock. Once it knocked me to the floor.

I have spoken to electricians in the past who have told me it's not possible. They've rolled their eyes and raised their eyebrows when I argue that I know from first hand experience that it is!

I understand their doubts though, as I know enough to know that plastic is not a good conductor!

Also, I'm not the only person to have felt this strange phenomenon.

It's not too much of an issue as with it being a two way switch the lights can be switched off from another point, but what are your thoughts on this?

 

[ColJack]

there is no possible way that touching the plastic will give you a shock.. plastic is an insulator.

it is hhowever possible that you touched the metal screws holding the switch and that they are possibly live due to a fault / clipped cable in the switch..

with the power off, remove the screws and see if the cable inside looks damaged or might be under the screw when they are tightened ( if they could be, gently bend them out of the way )..

 

[RonnyRaygun]

it is however possible that you touched the metal screws holding the switch and that they are possibly live due to a fault / clipped cable in the switch..

Yeah, I thought that too, so firstly changed the light switch (Still got a shock) then covered the screws with insulation tape (Still got a shock).

Did wonder if it was maybe the discharge of static electricity, but only seems to happen when touching this particular switch...and you can't discharge static electricity by touching plastic, right?

 

[ColJack]

would this switch be in a room with laminate flooring?

in an area subject to lots of airlfow?

it's possible to charge the plastic itself and then for the static to jump to you rather than the usual way of from you to earth ( via something metal such as a door etc.).., but the switch would litteraly have to be in a wind tunnel with dust / sand etc constantly bombarding it..

 

[RonnyRaygun]

would this switch be in a room with laminate flooring?

It is now, but was carpet last time I went near the switch!

in an area subject to lots of airlfow?

Yeah, it's a through room, the dining room being between the kitchen and the hallway. If front and back doors are open (or windows) the airflow can be high.

it's possible to charge the plastic itself and then for the static to jump to you rather than the usual way of from you to earth ( via something metal such as a door etc.).., but the switch would litteraly have to be in a wind tunnel with dust / sand etc constantly bombarding it..

I see what you're saying, but my mum is quite particular about her hoovering and dusting!

 

[electronicsuk]

I think you can only prove this to yourself by performing a test between the plastic face of the switch and a known good earth, to see what potential exists there.

I would originally have suggested dirt buildup that has created a path between the gap around the rockers and the internal contacts, but you've changed the switch, so that's out.

 

[mikhailfaradayski]

Hi Ronny,

Does this problem happen every time you touch the switch or is/was it intermittent?
(Just work from memory, im not suggesting you should try it again )

 

[madmole]

Plastic may not be a good conductor, but its more than possible a film of polish, cleaning agent or some other substance has been wiped over the switch and is a better conductor

I know you all hate then, but maybe a neon screwdriver would be a good test in this instance to tell is its mains or static

Get a cheap neon screwdriver and with a finger on the flat end, touch the screwdriver tip against the switch then the screws while watching the light

If nothing happens, then the effect is static, if it lights and instantly goes out its a large static charge , if it lights and stays lit, then turn off that circuit and get an electrican in, do not touch the switch

When you changed the switch, was there an earth wire and was it connected to the correct contacts? Was the back box metal or plastic and if metal, did an earth get connected to the back box?

 

[RonnyRaygun]

Does this problem happen every time you touch the switch or is/was it intermittent?

Haven't touched it for quite a while but don't think it was every time I touched it...but more often than not...

Plastic may not be a good conductor, but its more than possible a film of polish, cleaning agent or some other substance has been wiped over the switch and is a better conductor

But it's only the one switch. Seems unlikely that this effect would only happen on one switch in the house

When you changed the switch, was there an earth wire and was it connected to the correct contacts? Was the back box metal or plastic and if metal, did an earth get connected to the back box?

The back box is metal. Can't be 100% certain but I'm sure I would have reconnected the earth. I'll check next time I'm there.

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[madmole]

But it's only the one switch. Seems unlikely that this effect would only happen on one switch in the house

Not suprising if its the only switch with an internal wiring fault making the screws live and the film is conducting from them

But it would happen all the time. If its intermitant then it sounds like static. But still means the switch is conducting somehow, cos it needs to earth you to discharge the static from you

 

[TicklyT]

Unfortunately the presence of a CPC in a cable is no guarantee that it is correctly connected to earth at the other end.

If someone botched the wiring of a 2 way switch elsewhere in the house, misusing a CPC as a 2 way strapper, and later the CPC of the offending switch was connected to that in the assumption all CPCs are earthed, it could render the offending switch live, but only when another switch in the house is left in a certain position.

Just to make it hard to detect, probing with a meter when the incorrectly wired switch is in the opposite position will show the CPC to be earthed (via the switched live, lamp filament, neutral and neutral to earth bonding). Not a good earth maybe, but good enough to show continuity.

That is just one reason why a CPC should never be used for any other function, and anybody doing so should be severely beaten with a sock filled with their own excrement.

 

[big-all]

That is just one reason why a CPC should never be used for any other function, and anybody doing so should be severely beaten with a sock filled with their own excrement.

raotflmao nearly choked on my coffee
[ps got a weblink ]

 

[ban-all-sheds]

anybody doing so should be severely beaten with a sock filled with their own excrement.

That sounds like it'd be pretty unpleasant for the person delivering the beating too.

I think they should be made to beat themselves with the sock.

[ps got a weblink ]

If you want one, there's probably one out there somewhere.

 

[flameport]

If someone botched the wiring of a 2 way switch elsewhere in the house, misusing a CPC as a 2 way strapper, and later the CPC of the offending switch was connected to that in the assumption all CPCs are earthed, it could render the offending switch live, but only when another switch in the house is left in a certain position.

I have actually seen something like that.

2 way switching, wired in 3 core cable with no cpc (old cable).
Someone fits a metal lightswitch, but had bought a one way type.
Three wires - red/yellow/blue.
Red and blue into the switch terminals, yellow into the earth terminal.

The switch at the other end was hidden out of sight and (fortunately) was never used.

 

[Steve]

Plastic will conduct static electricity.

Do you wear tracksuits?