Strange Fault

[Spark123]

If the supply is TT and you have a normal split load consumer unit with non-RCD protected ways then you need to get a qualified electrician to sort it out ASAP, a fault on a non-RCD circuit can liven up all of the exposed and bonded extraneous conductive parts in the premises and won't disconnect automatically owing to not enough current flowing. This will give you odd readings too, usually something like a L&N reversal.

For what it is worth, volt sticks are excellent for fixing mains xmas tree lights, they are not much use for anything else.

 

[viewer]

You may have answered your own question - rats. The problem got worse as the insulation was eaten away. In addition, a corpse will provide a connection. Need to work through visually as well as electrically. A few years ago a chemical plant in Germany (?) caught fire and discharged tons of pesticide into the river with awful results. The cause of the fire was a rat chewing through cables.

 

[bernardgreen]

Corpses that have dried out can also ignite, not very often but it is a risk.

 

[steviez]

Been back today to take another look. I have now stripped all circuits from the CU and just left a test socket fed to the CU via 2.5mm T&E. When nothing is plugged in to the socket all seems fine and the RCD stays on, as soon as anything at all is plugged in to the socket the RCD trips. Any ideas?

 

[1550]

With out going on and on as you are having a rewire anyway it sounds as though you have an earth fault or a borrowed neutral, as you haven 't touched the other circuits that doesen't seem likely. More likely is the rodent damage you referred to earlier .Try taking the other neutrals out from the other side of the board , if it is still the same you have found a faulty circuit. Without proper test gear you will be on forever, best to get help , save you loads of grief. You must find out your earthing arrangements regarding TT. You need to make sure this is safe regarding RCD protection if needed.

 

[steviez]

Thanks for the reply. There is no other wireing in the board now apart from the 2.5 t&e to my tester socket. The earth comes in to the house via a 6mm earth in to the ground out side. The main electric feed comes on the side of the building.

 

[1550]

Thats a faulty circuit then . Wire the rcd as a radial with a single piece of cable if this holds and allows power consumption your rcd is OK. Are the tails and connections that are left tight.
Is your test cable part of the ring?

 

[1550]

That must be a TT system then. It is very rare that you will get disconnection times on a TT system You will almost certainly need another rcd on the unprotected side of the board. You must get this checked and addressed.

 

[steviez]

the test cable i have in place is just connected to a 16a mcb on the rcd side on the board. there are no other circuits in the board now.

 

[1550]

What is your voltage between L+N at the main switch . You need to get this tested without gear you will get nowhere. Is what you are using to test ok?
It should hold if the rcd is OK on one circuit as you have done . Get it tested , only answer.

 

[RF Lighting]

 

[1550]

I Know ;I'm just to soft , hate to see people in it.

 

[steviez]

what pics do you need?

 

[RF Lighting]

One of your CU with the cover off.

Leave everything as it is, including the connections for your temporary socket, and I'll tell straight away what's wrong.

 

[gnattycole]

Could this be a dodgy neutral? This might account for the fact that the RCD stays in until something is plugged into the socket. As soon as a potential exisits to the neutral, it rises instead of remaining at zero potential. I had a similar problem a while back with a clients garage supply. The neutral terminal was loose in a JB inside the garage and it kept tripping the RCD. Check terminations from the overhead supply to the RCD and from the RCD to the board, assuming this is a TT system.

Regards,

Nat.