• Welcome to the new forum. We're now hosted on ElectriciansForums.net rather than ElectriciansForums.co.uk - Chat about the forum upgrade by CLICKING HERE

Welcome to our Electrical Forum - We started out providing electrical advice just for the UK - But now we have specific advice for the USA too! - Register for free and share American Electrical Advice.

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


Regular EF Member
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.
Professional Grade LED Lighting Strips


Electrician's Arms
What’s the RCD mA rating?


In echoed steps I walk across an empty dream.
Staff member
You are isolating it from any other influence, just switching off the protective devices only eliminates the line conductors.


Regular EF Member
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.
  • Like
Reactions: Dan


Regular EF Member
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....

Electrician Talk

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
Electrical 2 Go - Electrical Supplier and Electrical Wholesalers
Electrical Insurance