This has been the bone of much consternation at work lately so apologies if this seems to be an obvious question but the argument thats been going on is whether 110v is actually safer than 240v? The accepted wisdom is that 110v in the event of electrocution is 55v across the earth and so much less likely to cause cardiac fibrillation and resulting death. But, the argument has been put that in order to make 110v tools effective, the amperage is usual double that of 110v and its the amps that do the real damage. There is so much contradictory opinion and I'm not an electrician, only having a slight increase of awareness of a 'lay person' so looking for an education from the more knowledgeable members here.

Grandfather worked for many years on the High Voltage pylons - his training always led to the amps being the killer, and making sure he was not a link to ground. Fusing and distribution board protections rate similarly in the work environment regardless of 110 or 240 so it then becomes a question of how much force (voltage) is pushing the current from the supply. Given the choice we prefer cordless tools, 110V second and 240V as an absolute last resort even though 240 is the standard in our homes and offices! Back to Physics "101" and Ohms Law where Volts = Amps x Ohms If Ohms are the same human body then 240 Volts is more than double the Amps of 110 Volts The real issue comes from involuntary muscle spasm due to the "let go threshold" I.e. the point at which muscles involuntarily contract tightly gripping the source of electrical supply - another of Grandads gems was to validate a supply isolation with the back of the hand before continuing work. Not properly isolated your arm would jerk away from the supply rather than tightly gripping it. It is here the lower voltage of 110 shows its benefit as the route a cross the body is by skin conduction - increase the voltage to 240 and it shorts through the body including potentially the heart resulting in fibrillation.

So what about 400 volt tools such as 3 phase circular saws for sawing intoconcrete slabs? Before we can discuss, we need more information. Are we in a clean workshop environment, a muddy constructionmsite.......

I wold permit them all and ensure that 240V has an RCD fitted. Stephen

I'd not spotted this until stillp's post I'm not THAT old, but this was exactly what I was taught when I was an apprentice! I prefered to use my AVO though ....... most of the time. Was a good way to clear an hangover ;-))

Retired many years before the appearance of HASAW - no meter but a tester knocked up by the company workshop, the back of the hand being a double check just in case the tester broke between making sure it was working and then testing the isolation.