a fuse / MCB will never trip if you come into contact with a live wire. there is just too much resistance to gte enough current to flowSidewinder, thats what i thought originally but think thats how fast it should trip when a 30mA current would flow. 30mA is the point at which the body can withstand without such serious consequences such as loss of consciousness hence why the regs state a 3omA rcd should trip in 0.4 seconds.
From what i have worked out i think at 13-15mA which is the point of involuntary muscle contraction a fuse should trip within 1 second but wondered if anyone else had any other thoughts.
animals are more susceptible to shocks than humans, especially from electric in the ground (lightning, dodgy cables (such as the horses at a racetrack a few years ago)), due to the increased distance between front and back feedThere is no hard and fast rule that could be used to determine the
resistance of the human body. This means that it is almost if not
completely impossible to determine the current that would flow when
a human body is subjected to a given shock voltage, either under
conditions of direct or indirect contact.
I think Andy has hit it on the head; the body resistance IS too
high to permit such a current to flow that would cause a protective
device to operate.
30mA was chosen as the setting for additional protection because
it is less than the 50 mA threshold at which the more serious effects
of electric shock are experienced.
I recently had a check-up for Carpal Tunnel and this involved the
passage of electric currents up each arm. The display was clear.
Test currents were passed up each arm at 30mA. I felt no serious
or lasting ill effects but the path of the current was nowhere near
the old ticker.
I would be interested in what someone like Apache says about this
topic. He may confirm that livestock is FAR more susceptible to the
effects of electric shock than us humes.
Could Sidewinder post a link to that site if it is available?
Does anyone know how fast a fuse or circuit breaker must disconnect if someone is receiving a shock and cannot let go?
At approx 13-15mA it causes involuntary muscle contraction and may prevent someone from letting go.
a fuse / MCB will never trip if you come into contact with a live wire. there is just too much resistance to gte enough current to flow
How would you know that Canoeboy?Canoeboy said:And the fact most have 4 feet not 2 and have wet feet generally and are stood in slurry, water etc etc in some circumstances
Years (thats lots) ago we used to do milking parlours, cows could feel a tingle when a 10mA trip stayed in if the conditions were right
Sorry?When testing RCD`s (of the BSEN variety) they should operate at less than 300msec for 1x their rating and less than 40msec at 5 times their rating
Bs4293 are 200ms at 1x , bsen61008 are 300ms at 1xSorry?
The "BSEN" variety?
As compared to what?
All the RCDs I`ve ever come into contact with have a numeric descriptor for their standard compliance,
There are the older BSxxxx RCDs; but there are also many, many different "BSENxxxx" types, too.
There is NOT a generic trip time for a "BSEN"
fyi - 60898 is a "BSEN" number - but won`t trip within 300mS until you`re long dead, if you`re the shock path.
Clarification please
. For some reason (beyond me) the older RCD`s must operated 100msec quicker, although how often do they ever get antwhere near that operating time in reality.
Enter your email address to join: