New FB RCCB tripping

[JohnW2]

Ok... The busbar wasnt cut so was joined between both RCCB’s

Ah, so I was probably not too wrong when I wrote ...

... Does not this not suggest some sort of cross-connection between circuits on the two 'sides' of the new CU - perhaps due to a wiring error when the CU was recently installed?

Mind you, I'm surprised that you did not have more problems than the one you described if that was the problem. Has the busbar now been cut?

Kind Regards, John

 

[John D v2.0]

Ok...

The busbar wasnt cut so was joined between both RCCB’s

That's impressive, are you sure? It would explain them both tripping but how do either stay up when anything is in use on that side? So what I'm wondering is whether the neutrals are also cross connected? Either way as soon as you used anything, both would trip?

 

[houstonwehaveaproblem]

Ah, so I was probably not too wrong when I wrote ...

Mind you, I'm surprised that you did not have more problems than the one you described if that was the problem. Has the busbar now been cut?

Kind Regards, John

Yes

 

[JohnW2]

That's impressive, are you sure? It would explain them both tripping but how do either stay up when anything is in use on that side? So what I'm wondering is whether the neutrals are also cross connected? Either way as soon as you used anything, both would trip?

Indeed - as I recently wrote, I would have expected that error to have had far wider consequences than what was described!

Kind Regards, John

 

[EFLImpudence]

The busbar wasnt cut so was joined between both RCCB’s

How is that possible with two RCCBs?

 

[JohnD]

some CU's are made with a long busbar that you cut to suit the way you will use it.

For example a 24-wide one could be 20-4 or 12-12 or 18-6

If the installer didn't understand, he might fail to cut it.

edit
this is one (old type)

 

[flameport]

some CU's are made with a long busbar that you cut to suit the way you will use it.

If this wasn't cut, surely that would result in both the L and N connections on the RCD being connected to the same bar, the result being a very large bang.

If the installer didn't understand, he might fail to cut it.

If they didn't understand, they should not have been installing it.

 

[houstonwehaveaproblem]

Not sure im reading this right!

The rccb’s are at each end of the board with the mcb’s in between.

The bar was connected between each rccb positive terminals and each mcb

 

[JohnD]

perhaps not, observe the "right handed" and "left handed" orientations.

I haven't got a pic of one with two RCDs

I agree the installer may not have been competent

 

[houstonwehaveaproblem]

Its one of these...

 

[JohnD]

yep, that could be done.

for all I know they might come from the factory with a busbar like that.

 

[JohnW2]

If this wasn't cut, surely that would result in both the L and N connections on the RCD being connected to the same bar, the result being a very large bang.

One would have thought so (depending on what had been connected to the other sides of the RCDs. However, is it possible that (perhaps not unreasonably) the busbar was only long enough to reach from the 'inboard' terminal of the first RCD to the 'inboard' terminal of the other one (when they were as far apart as possible) and that the other sides of the RCDs were wired in a manner which avoided the bang?

If they didn't understand, they should not have been installing it.

Whatever was done, it's hard to see how they could have 'understood'

BAS doesn't seem to have noticed this thread yet

Kind Regards, John

 

[JohnD]

yes, in my second pic it could have gone from terminal 4 in the LHS RCD to terminal 2 in the RHS RCD

The makers would have intended a segment to be nipped out to prevent the two sides meeting.

 

[EFLImpudence]

I shall have Mr.Carmichael after me for never having come across one like that.

I dare say I would have understood, though.

 

[JohnW2]

I shall have Mr.Carmichael after me for never having come across one like that.

Yes, you might!

I dare say I would have understood, though.

I'm sure you would. Even little me, who has never been anything remotely like an electrician, managed to diagnose the general nature of the problem - although I confess that I didn't dream that it would be such a monumental ***up as appears to have been the case!

Kind Regards, John