MCBs

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If practicable I would simply swap the MCB for another one (one that is compatible with the DB and with the same rating of course). This could identify the problem very quickly.
or move the circuit to another MCB of the same rating

 
9 Amps of lighting that is quite a load what sort of lighting is it? welcome to the forum by the way.
What type of lights?

e.g 9 Amps of flourescent lights will have a very high start up current.

Some more detailed measurements are needed and look at the possibility of splitting the circuit into two.

 
What type of lights?e.g 9 Amps of flourescent lights will have a very high start up current.

Some more detailed measurements are needed and look at the possibility of splitting the circuit into two.
My thoughts entirely.

Doc H.

 
When I posted My reply, I answered on the pretense that the MCB would be completely removed from the CU and all wiring unterminated :) AndyGuinness
why? just switch off the main switch if your worried, but testing continuity when live with the mcb is on is fine anyway, as there will be 0v across it.

 
When you say test the mcb, do you mean check if it's operating at the correct current, or that it allows corrent to pass through it ?

If the mcb is lying on the bench, switch it to the 'on' position and use a continuity tester or low resistance ohm meter to check for continuity between the bottom, where it (usually) connects to the busbar,and the top, where the outgoing circuit is normally connected.

If the circuit breaker is installed in the board/ consumer unit,(assuming the main switch is on) and the busbar is live. Using an approved voltage indicator, measure between the top of the circuit breaker and the neutral bar. You should read the supply voltage. Simples !!

Testing the cuircuit breaker for correct operation is a little more complicated.

You will need the operating characteristics for that particular breaker,an adjustable load of some sort and a clamp ammeter. Best of luck !!

Speedster.

 


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