I ask because holding the probes of an ohmmeter one in each hand, and with wet palms, I couldn't get the reading down to 8 Kohms, the value which on 240V would pass 30 mA. 20K was the lowest I could manage by gripping tightly. Yet I suspect one could get a very nasty, possible fatal, shock if 240V had been applied instead of the 15V. from an old AVO Mk 8. How is the 30mA. trip current arrived at? Is it the current which will kill only 50% of the population? In N. America (admittedly a place where there used to be far more ambulance chasers) the usual limit is 5mA. Are there any statistics showing deaths which occurred despite the presence of an RCD?

Skin is not an ohmic conductor. It looks somewhat capacitive[1], so the impedance drops as the frequency goes up. It passes less current at DC than it does at 50Hz. Likewise flesh - you can get a lot more current to flow at 500KHz... Theo [1] It's actually more complicated than that, there are various cell effects that kick in as the frequency rises, but the general trend can be thought as behaving a bit like a capacitor.

ARW expressed precisely : Did you actually mean 240v x 1.41 ?

Maybe I mean 253 x 1.41? It's an allowed voltage. You save the 1000v megger test to fuck up the decorators radio when he keeps plugging it back in when you are testing 1000V across his radio makes FM sound like DAB.

Do RCDs actually work?

Jul 24, 2014 106 Replies

Rate this thread:

Mike Barnes 11 years ago

"Leftover pizza"? Sorry, I don't understand.

Vote

ARW 11 years ago

I call it breakfast.

Vote

John Williamson 11 years ago

You've lost *me* there, too. Left. over. pizza. The words make sense when read one at a time...

Pizza over left? Nope. Over pizza left? Nah...

Vote

Windmill 11 years ago

:-)

Vote

Harry Bloomfield 11 years ago

Did you actually mean 240v x 1.41 ?

Vote

Capitol 11 years ago

I've recorded up to 1700V transients.

Vote

ARW 11 years ago

Maybe I mean 253 x 1.41? It's an allowed voltage.

You save the 1000v megger test to f*ck up the decorators radio when he keeps plugging it back in when you are testing 1000V across his radio makes FM sound like DAB.

Vote

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required