Electric Shock - Ouch!
- Thread starter markc
- Start date
MapisM
Well-Known Member
Actually, I believe that they are two separate units, with the MCB wired downstream of the RCD.
Or is the combo called RCBO in English regardless of whether the two functions are handled by a single unit or not?
Happy to stand corrected.
MapisM
Well-Known Member
Sounds like he's Italian, judging by the (actually rather funny!) email...
Portofino
Well-Known Member
Sounds like he's Italian, judging by the (actually rather funny!) email...
Good spot .
Incredible work ethic ,his vans IT reg he covers San Remo to St Tropez - Sunseeker s call out “ depanarge “ guy .
Carries parts on the van so fixes there and then. Returns with new as arranged / quoted and fits new takes his “ spare “ off
Think about it a client on charter
Hobs knackered - can,t cook
Ice maker knackered - no ice for rose
A simple socket in a guest cabin ,can’t charge a device- ruining the hol - oh no !
Chargers packing up are very common apparently he tells me , second is toilet motors .
Seastoke
Well-Known Member
I think they are a single module but you are right they are separate
superheat6k
Well-Known Member
To clarify the RCD: current in must equal current out within a margin of 30 ma (30 thousandths of an amp). The current rating for the breaker is the current it will allow to pass before tripping, e.g. 40a.
30 ma is the borderline safe limit that a human can generally withstand without suffering a significant electric shock, but in certain circumstances even 30ma can be dangerous and you can still feel a substantial jolt. 30ma is almost universally used as the setting for RCDs.
The C refers to the curve speed of breaker operation. B is medium fast and common on household circuits with only light inductive loads. C is medium slow and is used where slightly heavier loads may be prevalent with light duty electric motors (light inductive loads). D is for heavier inductive loads.
The reason inductive loads e.g. motors require a slower operating curve is because for a few moments at start up they will draw a relatively high current whilst they build up their inductance, which once established becomes part of the operational resistance or impedance.
The Merlin Gerin unit shown, is two separate units clipped together to form a continuous unit, if one trips it will trip the mating devices. In this case a two pole MCB C40 (C curve 40a) and an RCD with a maximum rating capacity of 60a with a 30ma leakage trip. I would expect these devices are linked in series on both Live & Neutral.
30 ma is the borderline safe limit that a human can generally withstand without suffering a significant electric shock, but in certain circumstances even 30ma can be dangerous and you can still feel a substantial jolt. 30ma is almost universally used as the setting for RCDs.
The C refers to the curve speed of breaker operation. B is medium fast and common on household circuits with only light inductive loads. C is medium slow and is used where slightly heavier loads may be prevalent with light duty electric motors (light inductive loads). D is for heavier inductive loads.
The reason inductive loads e.g. motors require a slower operating curve is because for a few moments at start up they will draw a relatively high current whilst they build up their inductance, which once established becomes part of the operational resistance or impedance.
The Merlin Gerin unit shown, is two separate units clipped together to form a continuous unit, if one trips it will trip the mating devices. In this case a two pole MCB C40 (C curve 40a) and an RCD with a maximum rating capacity of 60a with a 30ma leakage trip. I would expect these devices are linked in series on both Live & Neutral.
BartW
Well-Known Member
exactly,
the short between neutral and live with OP's finger didn't allow for a current reaching 40A, so didn't trip that side of the breaker,
(but still enough current to give OP a very unpleasant feeling ;-) )
and
there was no current from live to earth, (body isolated from ground)
so the RCD side of the breaker didn't trip either...
markc
Well-Known Member
Thanks Superheat and Bart for the info... it begs the question, what would I have had to have done differently to be confident that the breaker tripped, or would I have just bought the farm?
FWIW (and in danger of making me sound a complete numpty) about 25 years ago I cut a plug off a live cable with a metal Stanley knife whilst in the garden. I didn't feel a thing as I was saved by the RCD, but the stanley knife blade had a hole through it and bits of melted copper all over it. Perhaps this elevated my trust of of RCDs!
FWIW (and in danger of making me sound a complete numpty) about 25 years ago I cut a plug off a live cable with a metal Stanley knife whilst in the garden. I didn't feel a thing as I was saved by the RCD, but the stanley knife blade had a hole through it and bits of melted copper all over it. Perhaps this elevated my trust of of RCDs!
telsyork
Member
You should really carry out a test if you are in any doubt, the correct tester will check the tripping time and current at varying phase angles.
If you don't understand what you have just read maybe you should be looking for someone with more electrical knowledge.
My advice if you don't understand don't mess, it will kill you.
If you don't understand what you have just read maybe you should be looking for someone with more electrical knowledge.
My advice if you don't understand don't mess, it will kill you.
BartW
Well-Known Member
before working on electric cabling, you alway's need to make shure that there is no voltage on the wires,
you can do that with a volt meter,
before I start working on electric wires, that have been under power previously,
and after switching of the breakers, and or checking with a voltmeter,
the final check that I do, before I start the work =
I stroke the wire endings with the back side of one hand.
Apart from the risc of a very unpleasant electric feeling, this manouvre is not lethal.
(!...... don't do that at home if you're not familiar....!)
superheat6k
Well-Known Member
The classic issue with electricity is that it is perfectly safe UNTIL YOU FORGET IT IS DANGEROUS.
What you inadvertently did was formed a balanced partial short circuit, through you but with no earth path. The current flow was in and out through the part of your body where you felt the jolt. Had this been one hand to the other then the resulting shock could have been lethal as it goes straight across your heart. If it was the fingers of one hand then it would certainly hurt, but no further damage or harm elsewhere, thank goodness. This is why electricians work with one hand in their pocket.
In your previous situation as described the knife blade formed a full short circuit between the Live and Earth or neutral (which is also itself earthed) as it sliced through. The neutral is also connected to Earth at the supply source, so although you were holding the metal cased knife, the path of least resistance was the earth or neutral cable, rather than you, although had you had wet hands it could have been a different story,. This is precisely why it is called Protective Earth - it is your friend.
The severe damage that you observed at your finger tips was the result of the full short circuit, and in fact can momentarily reach hundreds even thousands of amps, so the momentary power for the brief few milliseconds before the RCD protected you would have been a function of I sq R, so assuming I is very high and is squared and R is likely very low the local power could reach say 200a x 200a x 0.5 ohms = 20,000 w. That is way way above a plasma cutter or arc welder and will easily blow hole through the Stanley blade.
I expect the arc was quite impressive, although a severe arc on its own can be very nasty because once the air is ionised is stops being an insulator and becomes an effective conductor, and arc flashes can cause severe burns and secondary shocks. Lightning is an arc through ionised air.
