Rcd issues

[Andyg4]

Hi new to the forum, but got a feeling I may be on here quite a bit. I recently had to do a board Change at work due to the RCDs on the split load board not meeting the disconnection times. With all circuits put away across the 2 sides of the board and all in the off/open position I energised the board to do the basic mechanical test on the RCDs, ie the test buttons. The 1st one closest to the supply tales serving breakers 1 to 5 operated fine and when tested 1x and 5x was fine and within the times. The 2nd RCD serving breakers 6 to 10 would not operate by the test button and would not disconnect in time when 1x and 5x tested. I swapped the RCDs over to prove a faulty RCD but with no joy as the 1st one now in the 2nd ones place didn't operate on the test button or within the times and the 2nd one in the 1st ones place operated fine within the times and on the test button. although the test buttons don't operate the RCDs trip approx 5 mins after being on with no load on at all. I'm left scratching my head a bit on this one. The only thing I keep thinking of is a possible neutral earth fault somewhere? Any suggestions would gratefully received. Cheers

 

[Simonslimline]

What dead tests were carried out?

And why did you have to change to CU?

 

[PEG]

Hi dude,you may need to disconnect your RCDs,and test,to identify the area of your issue...

 

[Octopus]

Can you confirm the tests you did prior to energising the board?

 

[davesparks]

This has been done to death on the forum, use the search function to find the other threads

 

[dave274]

its obviously not wired up correctly, id guess that you've got the neutral for rcd 2 in the wrong bar.

 

[davesparks]

its obviously not wired up correctly, id guess that you've got the neutral for rcd 2 in the wrong bar.

How is that obvious?

A much safer bet would be that there is a certain type of fault on one of the circuits which causes this behaviour. A fault which will show up of dead testing is carried out correctly

 

[telectrix]

How is that obvious?

A much safer bet would be that there is a certain type of fault on one of the circuits which causes this behaviour. A fault which will show up of dead testing is carried out correctly

seen it before. a N-E fault not necessarily on the same RCD can c ause this.

 

[dave274]

Well dave he swapped the board because of suspected faulty rcds. He's put a new board in and one rcd doesn't work, it's not the rcd because he's tried it on the other side and it works. So as there were no faults before and the rcd isn't broken so it makes it obvious that it's not wired up correctly.

 

[davesparks]

Well dave he swapped the board because of suspected faulty rcds. He's put a new board in and one rcd doesn't work, it's not the rcd because he's tried it on the other side and it works. So as there were no faults before and the rcd isn't broken so it makes it obvious that it's not wired up correctly.

How do you know there were no faults before? All we know is the previous board had suspected faulty RCDs, and that he jumped to the conclusion that the RCD must be faulty when thus board behaved unexpectedly.

This is the same story we get every couple if weeks on here when an inexperienced person with minimal training carries out a CU change on an installation with an existing N-E fault.

 

[plantpot]

Agreed
Rare for a RCD to be faulty always something causing strange results.
The world we live in now.
"My tyres gone flat can't be a puncture has I haven't gone over a nail I'll get a new van"

 

[Deleted member 9648]

Hi new to the forum, but got a feeling I may be on here quite a bit. I recently had to do a board Change at work due to the RCDs on the split load board not meeting the disconnection times. With all circuits put away across the 2 sides of the board and all in the off/open position I energised the board to do the basic mechanical test on the RCDs, ie the test buttons. The 1st one closest to the supply tales serving breakers 1 to 5 operated fine and when tested 1x and 5x was fine and within the times. The 2nd RCD serving breakers 6 to 10 would not operate by the test button and would not disconnect in time when 1x and 5x tested. I swapped the RCDs over to prove a faulty RCD but with no joy as the 1st one now in the 2nd ones place didn't operate on the test button or within the times and the 2nd one in the 1st ones place operated fine within the times and on the test button. although the test buttons don't operate the RCDs trip approx 5 mins after being on with no load on at all. I'm left scratching my head a bit on this one. The only thing I keep thinking of is a possible neutral earth fault somewhere? Any suggestions would gratefully received. Cheers

Well why not test for one then?....