live to earth short circuit tripped mcb but not rcd?

[securespark]

Is it not extraordinarily unlikely that even a complete idiot would/could manage to 'swap'/'cross' neutral and CPC connections in the CU?

From: https://www.diynot.com/diy/threads/guess-the-fault-competition.156922

 

[JohnW2]

Fair enough - it appears that the are no bounds to the degree of idiocy which can be displayed by 'complete idiots'

Kind Regards, John

 

[jim63]

Hi all, just an update, I had purchased a kewtech loopcheck 107, All my electrics seem to be in good condition and wired correctly after all, the green led loop tes led lights on all sockets, according to manual this means the earth loop is lower than 1.8 ohms, the loopcheck has an rcd test feature, on test the rcd did trip so it appears to be working after all, the other way I tested the rcd was using one of the above tricks, I first used the led tv, the second experiment was using a diall 4.7w gu10 led bulb which claimed to be 40ma, (Worst case if the bulb was 40ma, is 40ma flowing through your bodu survivable?) although on the current meter test it was drawing somewhere between 19 and 20 odd milliamps, I temporarly disconnected the neatral then connected earth, so the bulb was connected to live and earth, this tripped the rcd immediately about a second, It appears the rcd does work, As for the rcd appearing more sensitive in the past I can only conclude I must have had an appliance which had a bit of earth leakage but has then been replaced.
I am quite satisfied now that the rcd is working as it would save my life should the worst happen.

 

[Taylortwocities]

What you have done are very basic tests and not much different to pressing a test button.

The essential part of an RCD is that

• it will disconnect the supply at less than the rated trip current (nominally 30mA in your case)
• that it will disconnect within a set time period. The time period is checked both at the rated current, and 5 x the rated current. Tests are also done on both halves of an AC voltage waveform.

The 107 only applies a 30mA test environment for 300Msec, its a very basic check. A dedicated RCD tester is the only way to confirm that an RCD is actually working within these parameters.

 

[EFLImpudence]

(Worst case if the bulb was 40ma, is 40ma flowing through your bodu survivable?)

The bulb has nothing to do with the current that would flow through your body.

The critical factor is that it would be ~240 volts and the current throught your body is determined by the earth path resistance.

240V divided by (~1,000 ohms of your body + the resistance of the floor to earth {could be anything}) = ???
or
240V divided by ~1,000 ohms of your body touching a low impedance earth {oven carcass} = 240/1001 = 240mA.

Over 10mA is generally regarded as the threshhold above which your muscles contract and you can't let go.