Lights flickering, faulty mcb?

witnessmenow

Tl;dr: we have flickering lights on one circuit and it looks like the cause is the MCB, does sound right?

We've had flickering lights on one of our light circuits for the last while. The general wisdom online is that it's a missing neutral. Even mentioned it to a couple of electricians who we know and they thought the same.

I had a look at all the lights and switches and couldn't find anything loose etc but the voltage was measuring low (100v)

I decided to check the CU and voltage in to the MCB is fine, 235v but voltage as out of the MCB was the same low I measured at the light.

The MCB had two wires out, one presumably to the light circuit and one to the bell transformer. If I removed these from the MCB, the voltage measured ok.

But If I add any load to the MCB, I can see the voltage drop. More lights I turn on, the worse it is.

I tried the MCB without the bell transformer and seen the same issue.

I moved the lighting circuit to a different MCB and the lights worked fine, indicating to me the original MCB is bad.

Cu is close to 30 years old (I assume) and we have had to replace a few MCB in the past, but none manifested like this, they just wouldn't go back up.

Reasonable assumption it's a bad MCB and to get a electrician to change it out?

10-10-20

If you measure the voltage across the MCB when the circuit voltage is reading low, if it's working correctly then it should be very close to 0v. Any higher than that tells you that the breaker is the cause of the issue.

witnessmenow

Didn't think to measure across the MCB itself. Was just measuring to the neutral connection block. Thanks

witnessmenow

Electrician was able to come out yesterday and replace it, working perfectly again