Why I feel electric shock when I pressing a 24V control button?

[Kellenkula]

Hi there
Normally we know people won't feel electric shock if they touch a live 24V cable.
but when I was working in a factory, many operators including me feels got a short electric shock when pressing a 24V reset button. It has been like this for several weeks, operators start using pens to press that button.
Maintenance engineer says that is normal static electric shock...
But why we don't get this kind of shock in other control buttons, is there have any possible problem could make a control button have electric shock during pressing.

 

[PEG]

Hi,how do you know that it is 24v ?
I would suggest further inspection,rather than pressin' n' guessin' ?

 

[Kellenkula]

Hi,how do you know that it is 24v ?
I would suggest further inspection,rather than pressin' n' guessin' ?

That reset button is used to reset a SICK Safety light fence, according to the series, control voltage is 24V.

 

[PEG]

That reset button is used to reset a SICK Safety light fence, according to the series, control voltage is 24V.

Yes,but if that panel,or any transformers within,are supplied by other sources,the oppportunity exists,for a tingle of higher magnitude?

 

[Darkwood]

There are several possibilities here and it would mean a barrage of questions of which unless you know the control system wiring, various voltages etc you may have difficulty answering, what qualifications does your maintenance engineer have to make that claim, are they competent in following and understanding machinery control systems, do they understand floating voltages and how they can arise and the dangers they pose?

If this is static then the shock would be a rapid one which then disappears, does repeatedly touching the button give the same shock, if so this is unlikely to be static unless the machining process itself was generating a static voltage and the reset button was made and mounted in such a way it allow the voltage to ground through the person who next touched it.

 

[Marvo]

I'm not buying the static theory.

Just because 24 volts is required to operate a control it doesn't necessarily mean it won't give you a shock. If you supply one side of a 24v relay coil with 200 volts and the other side with 224 volts the relay will operate happily because the voltage difference across the coil is 24. The machine supervisor on the other hand will not operate happily if he comes into contact with any part of this '24v' supply because the difference between the 200v or 224v wire of the supply and the zero volt ground he's standing on is enough to give him a shock.

Voltage is a relative thing.

If people are using pens to operate the switch there's obviously a problem. Re-report it to the maintenance department and if they persist with the static theory then escalate the report to the health and safety responsible person / manager or escalate it through whatever channels are in place.

 

[dmxtothemax]

it's more likely that the panel/button is grounded
And that ground is for some reason now carring current,
That would explain the tingle.

 

[Chris1234]

We used to have an operator who was always getting electric shocks from the machines.
I told her to stop wearing wool jumpers!

 

[briwire]

Had a similar issue with a light barrier reset button mounted on a metal fence around a machine. The fence was earthed and the operators had to walk over plastic "steady-stak" conveyors to press the button. Their bodies were getting a static charge and when they touched the metal fence around the button, they got a quick crack of a shock. The H&S man made me earth the fence again, despite my explanation. They still get shocks, they also use pens.
As Darkwood says, if it is static, they should get a quick crack then nothing until they build up a charge.