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Just curious from a H&S standpoint.
Ta.
All electricity is dangerous from an H&S standpoint, tis not the voltage that kills you it's the current
As said above, depends on the current, and what protection is placed on the supply.
A car battery is only 12v but can supply enough current to kill a yak*
*may or may not have actually been tested
Okay - let me re-ph(r)ase the question.
If you opened an electrical cabinet that hadn't been isolated and touched a live terminal (assume normal workwear and dry hands) would it harm you?
'maybe'
amount of harm depends current, on how long you touch it, what your shoes are made from, whehther there's a trip/residual current detector etc.
Probably not* - I've zapped myself with 240V numerous times. I wouldn't recommend it, it tingles a bit, but as long as you don't grab down on something it's not bad.
*Obvious disclaimers apply.
...and if you think something might be live, touch with the back of your hand.
Short answer yes, long answer maybe
[i]..and if you think something might be live, touch with the back of your hand. [/i]
Or better still get the apprentice/office junior to.
From a H&S standpoint, any system with potentials greater than 50Volts is termed "high voltage" and must be protected and marked in a comensurate fashion.
Seperately, whether 120V is enough to hurt you really depends on the circumstance. The resistance of the human body varies dramtically, depending on the contact points. If you are wearing rubber soled shoes, and grab a conductor with a hand, and are not touching anything else (so the power must flow the complete distance through your body) 120v is unlikely to kill you. (it will SHOCK you, but you'd be unlucky to actually die.
however, do the same with wet hands, or in bear feet and you're dead!
Typically, 50mA is considered to be a lethal current, i.e. if your bodies resistance is low enough to cause more than 50mA to be driven through you by the voltage you run a very significant risk of death.
bear feet
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You know the test for most H&S stuff normally centers around what is considered "Reasonable". Now granted I'm not an Electrical engineer (but then as you are asking this on an MTB forum I'm going to make the not unreasonable assumption that neither are you) but in my opinion to [b][i]not[/i][/b] isolate a piece of electrical equipment before opening it up is a pretty dumb thing to do and as such any H&S assessment that does not require such an isolation would have to have a very very good reason behind it. N.B. "It's a bit awkward" or "we couldn't really be bothered" would not constitute a good reason.
It could very well be dangerous yes, depending on a whole list of factors. And even if the shock was not lethal or even close to lethal, you could get knocked backwards and smack your head. AFAIK this is a significant cause of death aside from the actual shock.
Or falling off the ladder when, while changing a light fitting, your ever-helpful mother turns the light switch on so you can see what you're doing.
A friend managed to, while in the attic of his West End flat, drop a live mains cable onto a gas pipe and blow a hole in it.
As someone who has had a lifetime's worth of electric shocks, I'd say you'd be unlucky to come to much harm. My first 240v shock was when I was three and I burnt the end of my forefinger off by shoving it in a light fitting and turning it on. My mother gave me a penguin biscuit for that, so a positive association was quickly formed between electric shocks and treats....
I once took the fuse out a 240/12V PSU without switching it off.
I made a very strange noise and my other hand smacked the underneath of the worktop I was at. I broke two fingers but thankfully nothing worse.
I once pulled the upstairs lighting circuit fuse and then proceeded to change a downstairs ceiling rose, grabbed live in one hand, neutral in the other to pull them apart - was a strange sensation and arms turned to jelly for about 15 minutes, but other than that no harm done...
Come on Derek, why do you ask?
The common sense " I prefer life to early death" approach is normally the best IMO.
Isolate
Test
Live.
Do not speculate, if in doubt consult a spark.
IME 120v 60hz is either marine installs or American kit, also bear in mind if phase 2 and 3 are in the same area you have a higher potential across terminals
I ask because I have come across some new build electrical panels for the US that have no electrical hazard labels. The kit is 120V 60Hz.
I once heard tell of an elecrtical lectuere who told all his students always to keep their left hand in their back pocket, that way the current wouldn't take a short path straight through your heart... It's a 120V hazard, so label it as such (though 110 V labels are easier to find)
Short answer, AFAIK, is yes it's dangerous from an H&S standpoint but I don't think it's above or below any specific limits other than the high voltage limits (which is quite high IIRC, 400+v). <edit, talking rubbish, see below>
Yes it's dangerous to touch and could kill you even at low current.
A car battery is only 12v but can supply enough current to kill a yak*
Not through it's skin it couldn't, you'd have to open it's chest and ram the wires into it's flesh right near the heart.
From a H&S standpoint, any system with potentials greater than 50Volts is termed "high voltage" and must be protected and marked in a comensurate fashion.
Not according to the standards?
High voltage (supply system) > 1000 Vrms > 1500 V electrical arcing
Low voltage (supply system) 50–1000 Vrms 120–1500 V electrical shock
Extra-low voltage (supply system) < 50 Vrms < 120 V low risk