shock!! no trip!

[eganelectrical]

When I wired my ccu I fitted all rcbo's. and tested all trip times etc. all passed!! In the garden mixing cement a few weeks later and water got all around the extension lead near the plugs! I didn't see this because it started getting dark! But Jesus I felt it with a rattle as I unplugged the mixer!
Went in the house and Rcbo for outside sockets still on! Checked trip times the next day and all still fine!! Surely this should have tripped??

 

[HandySparks]

If you bridge L-N with your chubbly little fingers, without allowing any leakage to earth, how can the RCD know? Still gonna hurt though...

RCD's are not a magic cure-all.

Just reading through the threads, and I was wondering whether someone was going to make this point. The OP, and almost everyone else is assuming a L-E fault path. If the fault is L-N, via the wet connector and the OP's fingers, the RCD function is irrelevant. So the OP may have had much more than 30mA through his hand without tripping the overcurrent protection. I guess that the level of current (if any) through his heart was low enough not to kill him.

 

[Engineer54]

If you ramp test most 30mA RCD's, you'll find they trip in the early 20's, so more like 2/3rds.

Agreed, but there are set out requirements that an RCD must meet on tripping mA. For example, must trip between X mA and Y mA (can't remember the mA ratings lol!!) to meet the BS standard!! Fault conditions are taken care of by faster tripping times...

....It's late here!! lol!!

 

[AndyOz]

An extract from a paper written by the IEEE is as follows:

Low-frequency electric currents of a few milliamperes flowing through the body cause muscular contractions. In the arm such an effect may make a subject unable to let go of a live conductor. The highest currents which 99.5 percent of men and 99.5 percent of women are able to let go have been shown to be 9 and 6 mA, respectively. Currents somewhat larger than this, in the range of 20 to 40 mA, passing across the chest may arrest respiration leading to asphyxia, unconsciousness, and even death. The most common cause of death in electric shock probably is ventricular fibrillation, a condition in which the circulation is arrested and death ensues very rapidly. An analysis of available experimental data indicates that body weight and shock duration are important factors in determining the maximum current not likely to cause ventricular fibrillation. Taking a weight of 50 kg as the average for a human victim it is suggested that the relationship between current shock duration is given by I = 116/??7, where I is the current in milliamperes and T is the time in seconds. It must be stressed that this has only been shown to be valid within the range of 8 ms to 5 seconds. Currents flowing through the nerve centers controlling respiration may cause respiratory inhibition, which sometimes persists for a long time after the current has been interrupted.

 

[Deleted member 26818]

My understanding, is that 6mA across the heart is sufficient to cause it to cease operating.
30mA from one hand through the body to the other, would not necessarilly cause 6mA to flow across the heart.
Current tends to flow along the outside of a conductor, a property known as 'skin effect'.
This also why fine wire conductors have a greater CCC than solid conductors of the same CSA, there is a greater surface area for the current to travel along.
As for the OP's question, it could be as already suggested, that the fault was not to earth, but from Line to Neutral.

 

[eganelectrical]

If you bridge L-N with your chubbly little fingers, without allowing any leakage to earth, how can the RCD know? Still gonna hurt though...

RCD's are not a magic cure-all.

Just reading through the threads, and I was wondering whether someone was going to make this point. The OP, and almost everyone else is assuming a L-E fault path. If the fault is L-N, via the wet connector and the OP's fingers, the RCD function is irrelevant. So the OP may have had much more than 30mA through his hand without tripping the overcurrent protection. I guess that the level of current (if any) through his heart was low enough not to kill him.

I bridged my thumb And forefinger across live and neutral once on a switch fused spur!
Fingers smoking!!

 

[Guitarist]

Was tracing some cabling inside galv trunking at a feed mill many years ago when I got 415v across the hand. Turned out the mice had been nibbling the inulation off. Taught me a valuable lesson that day.

 

[telectrix]

pesky meeces.

 

[wade88]

I think despite what we have all heard and read in speculation to the necessary current to do you any harm, it's safe to say.... being electrocuted AT ALL is a bad bad thing.

In fact, im guna take my chances with joining copper pipe together and getting wet instead (or pushing plastic pipe together). Seems like a much safer option.

 

[telectrix]

what puts me off plumbing is the cost of the full frontal lobotomy that is an essential part of the training.

 

[wade88]

I know a guy who does those on a discount....

Wood splitting axe to the forehead

 

[Jezeth]

Well call me a wuss if you like but I wear disposable rubber gloves on every job I do.............not ideal but a little bit of extra protection just in case.
Keeps my fingernails nice and clean too

Not a bad idea actually mate

 

[DPG]

10 year thread resurrection, cool!

 

[ELECNEWT]

JUST FOR INTEREST Showing current vs time effects of electric shock.