RCD TRIPPING

[choccy]

Hi all I have had a problem reported today about sockets in a property tripping the rcd.

Heres what has happened, the property has had some of the wiring upgraded and a new split rcd fuse board installed. Tests show that the existing wiring was ok to be used and only lighting and a few new power supplies were installed. Tested all of property and all results showing every thing ok so carried on and powered up property and everything ok.

Now after about 2 months a cleaner has been in and their hover is tripping some sockets, so back to see whats going on. Get there and both rcds are down and no power, so power up and ok plug in to sockets and ok:^O, then do in sulation resistance tests and everything clear, power back up and ok so far. Get some more equipment out to see if I can get it to trip and it does only on one circuit controlling 5 sockets through out house ( radial circuit )

split circuit and testing both sides of the radial ok, plug in and trips again. go to first socket in circuit remove the rest of the sockets from radial so only one socket on and ok( but when ever I put the rest of the sockets in to the radial they trip.

so me thinks that fault beyond the first socket in radial but tests are telling me they are ok.

Also on split board when the left hand rcd trips it trips both rcds in the board, but when you manually test the rcds they both trip at once and not seperately what ever one you test.

Thinking this could be a borrowed nuetral but i have checked and i have all the correct neutrals in where they should be.

So haveing a really good day so far and any kind of help from the more experienced would be greatly received. headbang

 

[kme]

This sounds more like a "crossed" live from a ring circuit - effectively bridging the two halves of the CU.

"If you haven`t found the fault - you haven`t done enough testing".....

Check ALL the outgoing circuits - with certain ones isolated, you should be able to seperate the RCD trips - the isolated circuits are likely to be the bridged ones......

KME

 

[choccy]

Thanks for the quick reply but I have taken the circuit out of play and evrything ok, but on your thinking if this was a split ring across the both sides of the rcd would the circuit not still be live when i have disconnected it from one side ? I have tested with the circuit disconnected and all other breakers on and it shows no voltage. But still interested in some more thoughts please, but also your suggerstion will be checked again hopefully tomorrow and thanks.

 

[Dunx]

Hi,

When you say 'after a few months...' has the property been unoccupied since the work was done? Often when both RCD's go it is a 'common fault to both sides' ie a borrowed neutral. But bear in mind that this could be within the CU! So my view would be to start again and disconnect each circuit [one at a time]at the CU and test that you have the right conductors ie do R1 + R2, if you can't identify each pair at the cu then double check you haver the right neutral for that circuit.

So assume now you have a phase and neutral pair, then do IR l/e and n/e. But you have to idendify the pair [live and neutra]l and disconnect otherwise you can get all sort of misleading results! Mark them with a bit of tape and then on to next pair.

If its a ring then do R1 + R2 and you should get same reading all round the ring,[ live to earth from opposite leg]. Remember a neutral fault can be dormant until a load is on the circuit.

Good luck!

Dunx

 

[steptoe]

are the neutrals from each RCD on the corresponding N bars.?

for the radial, you are going to disconnect every socket and reconnect one at a time,

could be a crossed NE somewhere.

if both RCDs going out together you really do sound like a split/borrowed N somewhere,

I like KMEs quote,

if you havent found the fault you havent done enough testing.

 

[choccy]

hi a quick update on the rcd tripping, went back today and found that the split neutral bars had continuity so there was a problem and this was tripping the rcd.

found that a radial circuit on opposite sides of the split board had a shred neutral. this was latter discovered that one of the existing lives had a break in it and the previous owner had took a leg from one of the radials and connected it. this gave them a supply from one circuit but a return neutral across both sides of the rcd.

So very happy fault found and wiring now correctly done and customer happy.

 

[Sidewinder]

Updates like this are very appreciated!

 

[SPECIAL LOCATION]

hi a quick update on the rcd tripping, went back today and found that the split neutral bars had continuity so there was a problem and this was tripping the rcd.found that a radial circuit on opposite sides of the split board had a shred neutral. this was latter discovered that one of the existing lives had a break in it and the previous owner had took a leg from one of the radials and connected it. this gave them a supply from one circuit but a return neutral across both sides of the rcd.

So very happy fault found and wiring now correctly done and customer happy.

Ahhh....

yet another one of the various flavors that the lesser spotted "borrowed neutral" beast can show itself in.

Some of the best wildlife presenters have to camp out for weeks to catch sight of one of these !!!!!

:Salute