RCD Keeps tripping

[James9292]

I have recently added two double sockets in a lounge original nor realising that the source was a spur that someone had already wrongly spure, so two existing double sockets a spur from a spur I then added 2 sockets across the room on a back to back wall essentially creating 4 spurs which obviously tripped the RCB.After realising the mistake I added a 13A fuse before the first socket to prevent tripping and make the original sockets safer also so the order now goes spured power into 13A fused split to feet 2 sockets that in turn feed 1 double socket each. Unfortunately the problem has persisted I have tested all sockets with a fault plug and all register correctly wiring and no faults. I don't know if this is earth leakage from an appliance or RCB failure the main CU only has 2 RCBs one for lights and one for the entire ring Main B32 30mamp load and another B6 for the lights and 1 MCB each which seems minimal

 

[pc1966]

I have recently added two double sockets in a lounge original nor realising that the source was a spur that someone had already wrongly spure, so two existing double sockets a spur from a spur I then added 2 sockets across the room on a back to back wall essentially creating 4 spurs which obviously tripped the RCB.

Too many spurs is more of a fire hazard as you can draw enough current to exceed the max limit of the cable. Typically your over-current protection is a 32A MCB but a ring final circuit (RFC) is wired in 2.5mm cable which is typically rated to around 20A (depends on installation method = thermal resistance) but safe for the RFC as there are normally two "legs" sharing the current to a reasonable degree.

If you have more than one spurred off a RFC you should have it from a 13A fuse connection unit (FCU) as you have done for this reason (basically treating it as a hard-wired extension lead).

A lack of that protective fuse would not trip a RCD.

After realising the mistake I added a 13A fuse before the first socket to prevent tripping and make the original sockets safer also so the order now goes spured power into 13A fused split to feet 2 sockets that in turn feed 1 double socket each. Unfortunately the problem has persisted I have tested all sockets with a fault plug and all register correctly wiring and no faults. I don't know if this is earth leakage from an appliance or RCB failure the main CU only has 2 RCBs one for lights and one for the entire ring Main B32 30mamp load and another B6 for the lights and 1 MCB each which seems minimal

Realistically you would be best to get a professional electrician in to check it out.

They would have the tools to test the cable insulation at high voltage for faults, and also usually to actually measure the leakage current and the trip threshold of the RCD to see if it is something "hard" like a damaged cable (N-E faults are often the trickiest to track down as L-E normally goes with a BANG!), or "soft" such as too much electronics plugged in to on the same circuit, all adding up the odd 0.5-2.0mA here and there, until you are close to the RCD's threshold.

 

[littlespark]

A spur from a spur wouldn’t trip an rcd.

an rcd or rcbo looks for an earth fault whereas an mcb looks for overload. (Nothing actually plugged in, no load)

you’ve done right by creating a fused spur, and by limiting the supply to 13A.

if the rcd trip is constant, check for a squashed cable behind a socket.

 

[timhoward]

By the way we have forum members in Liverpool if you need someone to take a look.

 

[LewisM]

Could be a nick on cable which is just touching the back box or a cable caught by the faceplate screws.

 

[James9292]

Too many spurs is more of a fire hazard as you can draw enough current to exceed the max limit of the cable. Often your over-current protection is typically a 32A MCB but a ring final circuit is wired in 2.5mm which is typically rated to around 20A (depends on installation method = thermal resistance) but safe for the RFC as there are normally two "legs" sharing the current to a reasonable degree.

If you have more than one spurred off a RFC you should have it from a 13A fuse as you have done for this reason (basically treating it as a hard-wired extension lead).

A lack of that protective fuse would not trip a RCD.

Realistically you would be best to get a professional electrician in to check it out.

They would have the tools to test the cable insulation at high voltage for faults, and also usually to actually measure the leakage current and the trip threshold of the RCD to see if it is something "hard" like a damaged cable (N-E faults are often the trickiest to track down as L-E normally goes with a BANG!), or "soft" such as too much electronics plugged in to on the same circuit, all adding up the odd 0.5-2.0mA here and there, until you are close to the RCD's threshold.

Would splitting the ring main onto more CBOs prevent th

Could be a nick on cable which is just touching the back box or a cable caught by the faceplate screws.

What is the best way to trouble shoot that as I'm guessing it would be to go over all the new connections in turn also this happens every 4 to 6 hours or more sometimes with heavy load items ie kettles etc also happens under low load in the night

 

[Mikegh]

Check IR at the spur with loads disconnected

If that's what you're saying you branched off a circuit

 

[James9292]

Check IR at the spur with loads disconnected

If that's what you're saying you branched off a circuit

Surely a fused spur would blow the fuse before tripping the RCB so could the fault be elsewhere

 

[LastManOnline]

this happens every 4 to 6 hours or more sometimes with heavy load items ie kettles etc also happens under low load in the night

Almost certainly a neutral to earth fault.

 

[UNG]

Would splitting the ring main onto more CBOs prevent th

What is the best way to trouble shoot that as I'm guessing it would be to go over all the new connections in turn also this happens every 4 to 6 hours or more sometimes with heavy load items ie kettles etc also happens under low load in the night

In what part of Liverpool are you, I'm out and about tomorrow so I may be not to far from you

 

[LastManOnline]

What is the best way to trouble shoot

Bearing in mind your level of experience I would advise you go back over all the electrical accessories you have connected, with particular attention paid to those secured to metal back boxes (as suggested in a previous post). If that fails to find it, I would suggest you get in a professional (as suggested in a previous post)

 

[johntheo]

Would splitting the ring main onto more CBOs prevent th

What is the best way to trouble shoot that as I'm guessing it would be to go over all the new connections in turn also this happens every 4 to 6 hours or more sometimes with heavy load items ie kettles etc also happens under low load in the night

Have you taken N to E resistance with the mains/RCD switched out?.

 

[James9292]

Have you taken N to E resistance with the mains/RCD switched out?.

No not qualified to mess with CU and I don't have the full test equipment my socket tester does everything except N to E fault unfortunately but I will be checking over all wiring for lose or bare/connections etc

 

[johntheo]

No messing with the CU required, with RCD/main switched off just check the resistance between N & E on any user socket associated with that RCD,

 

[loz2754]

Are we sure that it's an RCD that's tripping and not a circuit breaker. If it takes a few hours to trip, it could be due to the circuit being overloaded. Maybe...

 

[James9292]

Are we sure that it's an RCD that's tripping and not a circuit breaker. If it takes a few hours to trip, it could be due to the circuit being overloaded. Maybe...

Defo not the cbo its every time RCD

 

[littlespark]

Is it when things are plugged in?
First rule of rcd club is to unplug everything, not just turn off at the wall.
That rules out faulty appliances if the rcd continues to trip.

 

[pc1966]

Are we sure that it's an RCD that's tripping and not a circuit breaker. If it takes a few hours to trip, it could be due to the circuit being overloaded. Maybe...

It could also be a N-E fault that only shows up when something else takes a large current.

 

[johntheo]

If it is a N to E fault then you could expect this to show up as the current flow through a (the) neutral is increasing as there normally is only a volt drop or so with low flows which then increases with increasing current flows but even if there is only say 1 volt in the neutral cable at the fault location; a fault resistance of ~ 33 ohms will have no bother in tripping the RCD, a simple N to E resistance test with a multimeter could easily pick this up, if no fault the resistance will be infinity.

 

[James9292]

If it is a N to E fault then you could expect this to show up as the current flow through a (the) neutral is increasing as there normally is only a volt drop or so with low flows which then increases with increasing current flows but even if there is only say 1 volt in the neutral cable at the fault location; a fault resistance of ~ 33 ohms will have no bother in tripping the RCD, a simple N to E resistance test with a multimeter could easily pick this up, if no fault the resistance will be infinity.

I've had purchases an advanced kewtech plug tester that tests the loop and continuity also. Last night we turned off the power to the fused spur/s and it was still tripping does this mean that the fault has to be elsewhere? I am guessing at moisture or water in the outside sockets after this heavy rain etc!