Something strange

[a1guvner]

Hi all,

Thought i would throw this one out there,

Client has overhead supply coming into house and also has some outbuildings and requested a new supply from the DNO so he can have seperate bills for business use, i came along to fit a new dist board to the new supply, on this i fitted a split load board with 2 50 amp sub mains (existing) going out to the out buildings both with rcds upfront, when the installation was energised both rcds trip, so immediately you think got to be the neutrals on the wrong rcd, checked and all fine, turn on one supply and all fine turn on the other to the stable block and takes out both rcds even though they are going to different areas on the land and risk of a borrowed neutral somewhere is very slim,


anyone got any ideas why both rcds would trip

 

[JD6400]

Can you knock off all the circuits on the end of each sub and then energiser them one by one ? I would have the neutrals out as well !

 

[a1guvner]

Can you knock off all the circuits on the end of each sub and then energiser them one by one ? I would have the neutrals out as well !

did start with that but you could not get any consistency as it had seemed to hold when 3 mcbs were off at the end of the sub but would hold and fail with no consistency at all,

 

[malcolmsanford]

This is looking like a strip down of the sub boards here, neutrals out and reconnect one at a time until she pops,

 

[JD6400]

Are there any metal water pipes or anything like that linking the two sites in any way ?

 

[a1guvner]

This is looking like a strip down of the sub boards here, neutrals out and reconnect one at a time until she pops,

Granted... with a touch of tracing stuff out to find the possible borrowed neutral tripping the other rcd

 

[a1guvner]

Are there any metal water pipes or anything like that linking the two sites in any way ?

only in blue plastic,

 

[tony mc]

What about IR testining between neutral bars to see if it is the neutral!

 

[a1guvner]

What about IR testining between neutral bars to see if it is the neutral!

Could be worth a try, nothing ventured

 

[tony mc]

How did you get on with tracing the fault?

I hope its all sorted by now!

 

[alarm man]

ive had exactly the same.random tripping and different times with different circuits energised check for rat chewed cables in stables..

 

[JD6400]

Hi A1guvner , did you ever get to the bottom of the fault ?

 

[a1guvner]

Hi A1guvner , did you ever get to the bottom of the fault ?

Unfortuantely the client did not want to invest the money to uncover the fault and the installation is currently sitting on the single RCD and holding fine, did try my best to re-educate him it could show itself in the near future.

I guess it will be one of those unknowns, very annoying