RCD tripping using test button, N-E earth fault.

[Kev2632]

Hello, ive just been at a job today which i will be returning tomorrow which i have a problem with 2 Ring mains on the RCD,

*1 RINGMAIN 1
*2 RINGMAIN 2

Now when i switch on the RCD, and NO mcb's are on, the Test button doesnt work, and its the same when the mcb's are switched,

Then i tried disconnecting 1 of the neutrals from RINGMAIN 1, and put the RCD back on, the test button now works?

Why would this be happening? and is it a N-E fault, if so why doesnt the RCD trip straight away when the power is put onto the Circuits?

 

[needasparks]

Correct, I think it used to be called a sensing coil that the flux is created by but its been a while since i've I was at college so I;m sure someone will correct me,

 

[Kev2632]

Correct, I think it used to be called a sensing coil that the flux is created by but its been a while since i've I was at college so I;m sure someone will correct me,

yea im beginning to understand now what you mean, so when the faulty neutral was taking ouf of the neutral, the current flowing in the neutral live are now the same hence why it is allowed to trip on the test button is that right Needasparks?