Rcd tripping on board change

[byron24]

Hi all got a problem at a house where i changed the fuseboard the other day.

Replaced a wylex rewirable with a crabtree dual rcd board.

Both lighting on same rcd as sharing a common on the 2 way switching between upstairs and down.

Started to turn lights on and rcd tripped. Tried various rooms and turning lights on in different orders and rcd trips instantly sometimes and then after a few minutes other times.

Did insulation resistance tests between the earth bar and the line conductor for each lighting circuit and reading a dead short 0.00Mohms.

Did a continuity test between line conductors and earth bar and went round siwtching on different rooms. Some read open circuit and some came back with a reading of 40 - 100 ohms.

Cant see that there is a dead short on every other room as was all working before board swap.

Put them on the non rcd side and breakers stayed on.

Any ideas what might be causing this?

 

[Mr Mark Sparks]

i think you should be looking for a neutral fault remove all the neutrals and go through them 1 by 1 and do ins res tests

 

[coldelsol]

I had simular problem ,and agree with message nuetral fault .mine was the 2way lighting had borrowed nuetral which caused an unbalance .

 

[baldsparkies]

Agree with others, I always totaly isolate circuits before testing especialy with pme. Its the only way to get accurate readings. Look for continuity between the nuetrals when everything is disconnected. You should get open circuit readings unless they are shared. Make sure lamps are in and try light switches both ways. Stick to 240v on your tests, in this instance. Also its prudent even essential to do a periodic before a board change it shows possible problems in advance.

 

[coxy]

Hi I agree I now always test circuits before any board change or rcd install.Any n - earth fault will trip rcd not mcb - and you need to inform customers of the faults