Discuss MK 63amp RCD that fails Ix5 test everything else tests fine on the board in the Electrical Forum area at ElectriciansForums.net

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stuarth

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I have a brand new MK 63amp RCD that fails Ix5 test everything else tests fine on the board, I tested with all circuits off everything unplugged so swapped it for another thinking must have a faulty one but the same result, it will trip at 50ms and ramp tested at 33ma, ze=0.18 what could be happening? any advice on what could be wrong would be greatly appreciated.
 
It is failing to disconnect at 40ms
 
30ma
 
I did test with another tester with exactly the same results.
 
Ok, will try tomorrow if I can get access again, what is your thinking with disconnecting outgoing?
 
You are isolating it from any other influence, just switching off the protective devices only eliminates the line conductors.
 
Assuming isolating the neutral works what do I do to correct it? there are two existing RCBOs on the board which work well within the regs which I disconnected to test if influencing the RCD, they did not.
and you have left a fault rcd,tut tut.
not sure how much more dangerous a RCD tripping 10ms slower is but will be going back armed with more knowledge and tips on correcting it.
 
Could it possibly be partial hysterisis of the toroidal coil? Maybe there is some DC current causing this??? Maybe you need an A type instead of AC, just a stab in the dark there....
 
domestic, unable to get in today but should on monday
 
There’s no requirement in the 18th edition for RCDs to trip in any particular time.

As for this testing with all loads disconnected, what’s that all about?
Yes Mrs Miggins, your RCD works fine, as long as you don’t switch anything on.
 
There’s no requirement in the 18th edition for RCDs to trip in any particular time.

As for this testing with all loads disconnected, what’s that all about?
Yes Mrs Miggins, your RCD works fine, as long as you don’t switch anything on.

The note in 643.8 makes reference to compliance being achieved in terms of additional protection when the 40ms at 5x rating is met.
I just see that this information has migrated from section 415 and found a new home.
 
The note in 643.8 makes reference to compliance being achieved in terms of additional protection when the 40ms at 5x rating is met.
I just see that this information has migrated from section 415 and found a new home.
Yes, but it’s a note not a requirement.
The requirement now, is just to have 30mA RCD protection
 

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