Electric Shock off a Light Switch

[Deleted member 105018]

Hi. Wondered if anyone can offer some insight. Basically this isn’t my area of work in general so hence the post.

I was asked today to oversee an investigation into a potential electric shock when someone switched a light on. The shock was described as a “massive” electric shock that supposedly blasted the victim against the adjacent door. Victim was ok afterwards with no lasting effects. Nobody seems to have seen the incident.

The commercial spark ran his tests. Basically the light is a double gang plastic switch (think cheap) on a plastic surface mount box. Inside the earth cables are terminated together but not to the box as you would expect with it being plastic.

There were no loose cable or damaged cables in the box. The guy testing ran an insulation resistance test from the light fitting with the switch in the ON position and found it to be fine. Zs measured at about 1.5ohms on a 6A MCB. RCD test tripping at 23ms at 1xI and at 7ms at 5xI. Similar results at 180. Ramp test showed RCD to trip at 24mA. Earth continuity belled back to dis board from every accessory and found to be fine.

The spark didn’t have an explanation. Neither do I. Settled on replacing the switch itself. Anything we’ve missed? Any advice welcome.

 

[ferg]

I've been reliably informed by a customer of mine that it's probably due to an excess of electricity in the body.

I gave up in the end.

 

[ruston]

I get the occasional muscle spasm in my hands, it feels so much like an electric shock that I have to check around to see if anything is live that I could have touched.
Other people have seen this happen and assume I’ve got a shock.


Also I worked with someone many years ago who seemed to get electric shocks from everything, although she did always wear a wool jumper. She’s also long term sick now!

I get that too . I have degeneration of the spine , but my neck suffers the most . When the nerve traps in the neck it is just like an electric shock.
It affects the arms too. You should go for a check up.

 

[Chris1234]

Even this shock only “f**king hurt”, no mention of being thrown backwards or anything.
I believe the second time he touched it was a similar experience also!

 

[ruston]

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I get that too . I have degeneration of the spine , but my neck suffers the most . When the nerve traps in the neck it is just like an electric shock.
It affects the arms too. You should go for a check up.

 

[static zap]

I've been reliably informed by a customer of mine that it's probably due to an excess of electricity in the body. I gave up in the end.

..ask if they always killed digital watches ...!

----More about situation (Rainy or Dry day)....

Were they on their own , did they have to open any doors(using clothing rather than hands) ,pushing a trolley , or dragging plastic sheeting behind them.
..Had they recently got out of a car -Chauffeur assisted ?..
Any signs of a source of water .
(Does switch protrude to be used as a coat hanger on a wet day)

.. Maybe get replacement with cap covers over screws ..!

...returning to trolley--may be off it..

 

[dmxtothemax]

1.5 M ohms sounds big !
But it is not
I would expect much higher on plastic

 

[telectrix]

brain to feet elctrical impuse, as in get up and do summat.

I've occasionally experienced similar.
I'm sitting watching TV or lying in bed whatever, and completely out of the blue, it's like someone has zapped me, head to toe, with the mains. Then it's gone.

Weird!

that just happens on the rare occasions when the brain decides to shift into gear. .

 

[Intoelectrics]

I was asked today to oversee an investigation into a potential electric shock when someone switched a light on. The shock was described as a “massive” electric shock that supposedly blasted the victim against the adjacent door. Victim was ok afterwards with no lasting effects. Nobody seems to have seen the incident.

Me thinks somebody has been watching too much sci-fi! Or Judge Judy!

 

[richy3333]

He is talking rubbish. Not sure how anyone can get a shock from plastic.

You've not seen my wife's credit card bills then

 

[ChrisElectrical88]

Didnt happen did it, from what you have explained, i would happily go and disinfect and lick the switch to prove he was lying.

 

[BroadReach]

If you discount the throwing across the room bit, I have seen this in the past:

Electric shock on a plastic rocker switch. On further investigation I got 80-100V by putting a multimeter probe on the gap between the toggle and faceplate - to earth. On closer inspection this was full of dark black detritus.

This was in a kitchen and I imagine the switch being wiped with a dirty dishcloth over the years........

 

[Silly Sausage]

brain to feet elctrical impuse, as in get up and do summat.
that just happens on the rare occasions when the brain decides to shift into gear. .

You calling me lazy?

 

[DefyG]

Sounds like a job my mate Nige did, the biggest shock was that it actually worked!

 

[45140]

I work with MV and HV electrical. No-one gets "thrown" by an electric shock irrespective of the voltage.

A person creating a dead short against say 25kV can stay in contact with the equipment until recovered. I can see a person being pushed back where there is vapour in the air, which is converted to an expanding gas when the electric arc is created, but in those cases there would be hot vapour as opposed to electrical burns.

Had there been a high volume nylon carpet and insulating shoes, then quite a head of static electricity could build up in the body, and the discharge route would be via the metal screw securing the faceplate. If there was some sort of resultant effect on the muscles then the person could have suffered a spasm. Personally I think this is what has happened as the static discharge through the fingers would make a loud crack as well as being painful. Seriously dispute that this is a circuit-related electric shock incident.

 

[Strima]

Had there been a high volume nylon carpet and insulating shoes, then quite a head of static electricity could build up in the body, and the discharge route would be via the metal screw securing the faceplate. If there was some sort of resultant effect on the muscles then the person could have suffered a spasm. Personally I think this is what has happened as the static discharge through the fingers would make a loud crack as well as being painful. Seriously dispute that this is a circuit-related electric shock incident.

Plastic accessory fitted to a plastic backbox with the earths jointed together but not to anything else so the screw wouldn't be earthed.