shock!! no trip!

E

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??:mad:
 
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eganelectrical said:
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??:mad:
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Yeah that's odd would have thought the rcbo would have seen the imbalance in current they are normally quite good :s dodgy rcbo by sounds of things but you say you trip tested it and it tripped in
Good time ok?.. Sure there will be a lot smarter guy to give a better explanation I'm sure.
 
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10mA through you will give you quite a tingle till you let go, but it won't trip a RCD. and depends how well you are earthed.
 
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Did you check the trip times at the socket or at the rcbo in the board, this is sometimes a mistake by some sparks, as the earth may not be conneted in the socket, where the mixer was plugged in, or maybe the mixer hasnt a good earth.

Just a thought..
 
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Extension lead reel was probably plastic, so being wet probably didnt give a good enough path to earth, until you touched it, then you must have got less that 30ma.

would you be so kind to do it again but put a amp clamp round the live and neutral and let us know the leakage

please don't. I'm only joking
 
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The most painful and only cross body shock I've had was on a circuit with 30ma rcd protection, which didn't trip, but was later tested and passed.
Below 30ma hurts.

All the others have failed to reach the same level of pain.
 
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Did you check the half times test on both poles though? is your tester calibrated? what tester have you got? what make of RCBO have you installed?
 
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moose said:
Did you check the trip times at the socket or at the rcbo in the board, this is sometimes a mistake by some sparks, as the earth may not be conneted in the socket, where the mixer was plugged in, or maybe the mixer hasnt a good earth.

Just a thought..
Click to expand...

Yes mate I checked from the socket! Also tested in from ext lead plug sockets.
 
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electric will said:
Extension lead reel was probably plastic, so being wet probably didnt give a good enough path to earth, until you touched it, then you must have got less that 30ma.

would you be so kind to do it again but put a amp clamp round the live and neutral and let us know the leakage

please don't. I'm only joking
Click to expand...

Perhaps you can come and do it for me? "Electric Will". Hehe;)
 
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still haven't confirmed half times on both pole readings if any? and readings of all trip tests, plus my original question, lets have the full details then??
 
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well thats good readings for sure, did you test the ZS out of interest on the ring? I expect an appliance is the factor regarding the tripping, well done for the readings, I was expecting between 20-38 at times 1 and 8-18 at times 5 so looks good regarding the trip, what did you say the earthing method was? not that, that will be the reason why you had the tripping in this case, I just like being nosy.
 
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Earthing is a tnc-s. just felt like a big rattle in the hand so thought was over 30mA but as the others said 'can get a nasty one from 10mA' then this must have been below 30mA.
 
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A 30 ma trip should trip at 30% of the rating under fault conditions, this is why 3 computers which leak 2.5 ma are recommended not to be exceeded by 4 on a 30 ma trip, I have no evidence with me about this but have been told this is the case several times, maybe incorrectly haha, assuming there is something in this, just assuming then 10ma will be the danger threshold, actually there was a thread a couple of weeks back regarding the danger level and I think 10 ma was the figure some sparks suggested, if so your lucky you were not killed.
 
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MDJ said:
A 30 ma trip should trip at 30% of the rating under fault conditions, this is why 3 computers which leak 2.5 ma are recommended not to be exceeded by 4 on a 30 ma trip, I have no evidence with me about this but have been told this is the case several times, maybe incorrectly haha, assuming there is something in this, just assuming then 10ma will be the danger threshold, actually there was a thread a couple of weeks back regarding the danger level and I think 10 ma was the figure some sparks suggested, if so your lucky you were not killed.
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RCDs do lull us into a false sense of electrical security ! 10ma is bloody painful, you must have a heart of an ox ! thank your luck stars.
 
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MDJ said:
A 30 ma trip should trip at 30% of the rating under fault conditions, this is why 3 computers which leak 2.5 ma are recommended not to be exceeded by 4 on a 30 ma trip, I have no evidence with me about this but have been told this is the case several times, maybe incorrectly haha, assuming there is something in this, just assuming then 10ma will be the danger threshold, actually there was a thread a couple of weeks back regarding the danger level and I think 10 ma was the figure some sparks suggested, if so your lucky you were not killed.
Click to expand...

Can you explain this a little further please??
 
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Engineer54 said:
Can you explain this a little further please??
Click to expand...


Basically I have been told by an engineer and a rep from a RCBO manufacturer that they don't recommend more than 3 PC s on a trip, their thinking is on average with the monitor a computer can leak 2.5MAs, this has confused me and I have asked why, basically on one Job I have just done we had to install 6 ring mains in one room for 18 computers in Dado trunking, each of the 6 circuits rcbo protected, crazy?? well apparently they recommend 3 max per trip due to nusience tripping. I don't get this myself, your an engineer perhaps you can help me with it. then theres the 10MA situation, a couple of weeks ago there was a good thread about what amount of current actually kills you, I have heard 10MA, but always thought 30 MA, however a fair few sparks here said they had heard it was 10MA, if so and the OPs trip didn't go out when he took a whack I was wondering why it didn't go out, I asked for test results, he gave them, good readings, so, if a trip according to a manufacturer shouldn't have more than 3 computers on it due to nusience tripping and the death value apparently 10MA, and the trip didn't go out then hes kinda lucky? yes?
 
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I remember my lecturer explaining all of this, and it made perfect sense at the time because he was very good. However, age, kids, work and alcohol have made all the details go a bit fuzzy. What I do remember, is that it takes around 50mA to cause fibrillation in most people and the 30mA limit is to take allowance for the percentage of weaker people, like children etc. the time factor was also to do with fibrillation, and he did an amazing comparative drawing showing the electrical impulse for the heart and a 50Hz waveform. At no point did he say that safe and painless were the same thing.
 
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MDJ said:
and the trip didn't go out then hes kinda lucky? yes?
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Yes.

10ma is the ideal, shouldn't ever kill anyone.
30ma is the compromise, probability of death is extemely low, it would have to be the wrong person in the wrong situation at the wrong time.

No doubt if you stuck L and E directly either side of most peoples' heart on a 30ma, most people would have serious heart problems, I suspect the majority would die if no medical attention was given and the Rcd probably wouldn't trip.

I have and I'm sure plenty of other pople who work with electricity on a daily basis have had shocks. In theory we should all be dead, almost all of mine have been across the back of the hand or arm as I posted earlier only 1 across body and that's in 45 years of employment and a few years before that (I was an inquisitive child)
 
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partypest said:
I was such an inquisitive child as far as electricity was concerned, I should be dead. Maybe I've become immune to it? I'll just fetch a screwdriver and find out.
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When i was 10 / 11 I made up several extension leads with 2 pin male female connectors for train set power supplies, record player etc.
I had all the plugs with live pins exposed, you don't do Elec regs when your still in Junior school.
Minor shocks were the norm.
 
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44ALLAN said:
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:)
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Not a wuss mate. As a classical guitarist, I wear gloves a lot of the time too....tho not to protect me from shocks. :)
 
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MDJ said:
Basically I have been told by an engineer and a rep from a RCBO manufacturer that they don't recommend more than 3 PC s on a trip, their thinking is on average with the monitor a computer can leak 2.5MAs, this has confused me and I have asked why, basically on one Job I have just done we had to install 6 ring mains in one room for 18 computers in Dado trunking, each of the 6 circuits rcbo protected, crazy?? well apparently they recommend 3 max per trip due to nusience tripping. I don't get this myself, your an engineer perhaps you can help me with it. then theres the 10MA situation, a couple of weeks ago there was a good thread about what amount of current actually kills you, I have heard 10MA, but always thought 30 MA, however a fair few sparks here said they had heard it was 10MA, if so and the OPs trip didn't go out when he took a whack I was wondering why it didn't go out, I asked for test results, he gave them, good readings, so, if a trip according to a manufacturer shouldn't have more than 3 computers on it due to nusience tripping and the death value apparently 10MA, and the trip didn't go out then hes kinda lucky? yes?
Click to expand...

I was only interested in this statement...
A 30 ma trip should trip at 30% of the rating under fault conditions

​
An RCD has specific tripping characteristics for both fault and normal tripping for both mA and time. Never heard of this ''should at 30% of it's rating in a fault condition''.

As for the amount of PC stations on a RCD/RCBO, i've never had problems limiting such numbers to 5 stations. 3 seems to be a little OTT to me lol!!

The lethal current required, depends on too many factors and conditions to give a specific figure. and was all basically covered in that thread. 10mA is the RCD rating i use to protect communal shower room installations, and other higher risk areas throughout the hospital medical areas etc!!


As far as i can remember, 0.5mA = little sensation. 10mA = threshold of muscular contraction. 30mA = threshold of respiratory paralysis. 75mA = irreversible threshold of heart fibrillation. 1A = heart arrest!!
That's basically what i have always gone by anyway... lol!!
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Click to expand...
 
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