Trying to understand a fault

[studentspark]

Split load board
TNCS
30mARCD Tripping taking out all sockets, and boiler.

Tried to isolate problem by switching on MCB one by one to see which caused the problem.

Seemed to trip on multiple circuits

Stable with no load, but if a load connected on any circuit would trip intermittently.

Neutral Earth, was my thinking as its across different circuits.

IR reading did show 0.00 between N and E.

Circuit did work for a while though.
But if it was a reading of 0.00 how could it work at all.

I know that earth and neutral touching can trip the RCD as MCBs are single pole
The neutral of the circuit can still trip RCD if that MCB is off.

This is why it seemed like the fault was across multiple circuits ?

Is that correct.

Neutral Earth faults I am a bit unsure about.

Thanks

Ramp also showed a 21mA trip, Is that too sensitive, seems low to me.

 

[Wangerman]

If you have one the same I would swap over the RCD and then start backwards from there

 

[DetlefSchmitz]

Ramp also showed a 21mA trip, Is that too sensitive, seems low to me.

Down to 15mA is still in spec.

 

[1john]

did you have the individual neutrals disconnected whilst doing the insulation resistance test? did you have the main switch and RCD switched off (not just the MCB's)

 

[ricicle]

Are the Neutrals connected in the correct Neutral bar ?

 

[studentspark]

neutrals in right bar

power off when testing

Re power being off power. If power was on you would get an issue due to earth and neutral being combined? is that right

Tested neutral bar to earth bar got 0.00 so individual tests to all neutrals

all fine except one which was 0.00

 

[1john]

if you just switched off the mcb's you could get a reading back to the star point. the one circuit with the low reading is the one at fault, go around and unplug everything, faults are quite often on aplliances, although if cables have been ran near to heating pipes or any other work has been done a cable could have been nailed into, drilled through or trapped and damaged.