static electicity

[SkyWalker]

hi guys,

my mate phoned the other day asking my opinion on why when he touched the metal of a cassette unit he kept getting small static shocks, my honest answer to him was im not sure.

any takers on why this unit would do this, and does it posses any danger?

sorry no info on make/model it was last week and he is on hols now.

just interested in case i ever come across this in the future.

[Brian_UK]

What clothes was he wearing, what was the flooring material, what was he standing on?

It's nothing but questions, sorry :D

[nike123]

Are you sure that is static electricity? When you discharge static electricity by touching something, after that, there is no more electricity in flow.
But if it is still present after that initial touch, than that is not static electricity, that is problem with grounding of unit and unit has some electrical insulation damage.

[SkyWalker]

i did suggest testing the earthing but he never got back to me, he was standing on metal steps, wearing snickers trousers and t shirt (not sure what material), unsure on flooring never been to the building he was in.

i told him to test the unit cover (metal) to a known ground source, would it have shown a voltage if there was a problem? i cant help but think if there was insulation damage (to earth) it would pull silly amounts of amps and trip the MCB? am i wrong in thinking this?

[nike123]

i did suggest testing the earthing but he never got back to me, he was standing on metal steps, wearing snickers trousers and t shirt (not sure what material), unsure on flooring never been to the building he was in.

i told him to test the unit cover (metal) to a known ground source, would it have shown a voltage if there was a problem?

Yes it would!


i cant help but think if there was insulation damage (to earth) it would pull silly amounts of amps and trip the MCB? am i wrong in thinking this?Current depend on how much resistance is in its path and how big is potential diference. If insulation is not much damaged than resistance is bigger and current is smaller. Consequently, if insulation is badly damaged and path to ground (or any object with difference in potential exist between itself and faulty equipment) is low resistance, then current will be high and probably trip fuse.

[laf100]

Perhaps it was the Snicker Bars on heat feet causing the problem!!:o

Sorry, couldn't resist that one! More seriously, maybe if the air in the room was dry enough, the friction of the air "rubbing" between the plastic fan blade & coil may build up a charge?

That said, I have never cme across it myself though.

But I have felt a "buzz" from metal casings on a domestic freezer with earth problems on the house, and a display case with a partial earth leak, but no earth connnected in the plug.
:cool:

[Magoo]

Nylon carpet is the problem, you slip slop around and the first grounded thing you attach to discharges the static built up in your body, ZAP.
magoo