RCD Tripping

[Fluffy]

Hello everyone,

Am hoping you would be able to advise me here.  I am a retired sparks so a bit out of date with latest regs etc so posting in the DIY bit.

I have a split 2 bank Wylex CU with both banks protected by 80A 30mA RCDs.  There is a single socket just below the CU wired as a spur from the gnd floor RM.  Whenever I plug mr wifi router into this socket it takes out the RCD - sometimes both RCDs.  I have tried 2 other routers (one with an external power supply) and the same thing happens.  Even if I wire the router power lead directly into one of the circuit breakers it happens.  Weirdly, if I plug any of the routers into the wall socket 1 metre away it's fine.

Wylex tech support were stumped but suggested it could be a shared neutral issue - not sure if I agree with that.

I'm thinking it must be something to do with the surge of the transformer being so close to the CU? Thinking along these lines I plugged a 10 metre extension lead into the single socket and the router into the end of that but it still tripped.

In terms of a solution, I could look to getting one of the RCDs replaced with an isolator (being mindful of what circuits should and shouldn't be RCD protected of course) but that isn't really solving the reason of why it's happening.

I'd love to know what's going on here.  

 

[Evans Electric]

Check where the  spur neutral is connected  .  It can easily get connected to the wrong neutral bar .  

It MUST be the neutral bar that controls the relavent MCB  .  

Almost certainly this is the solution .

These  boards generally have  three neutral bars ....the normal incoming neutral bar ......the neutral bar for RCD  1  ....the neutral bar for RCD 2 .         If the live is on the RCD1 side , your neutral could be  in the RCD2 bar ..or .the incoming neutral bar . 

Don't hesitate to come  back if its not the case .

 

[Doc Hudson]

Wylex tech support were stumped but suggested it could be a shared neutral issue - not sure if I agree with that.

They symptoms you describe match up exactly with what some called a shared or borrowed neutral. All it is in reality is the live comes via one RCD but the neutral goes back via the other RCD, Whoever wired the socket did it wrong. Your "solution" to replace the RCD with a switch is daft to say the least, the RCD is functioning perfectly correctly by the sounds of it. Why remove something that is doing its job? The answer is to solve the fault, not remove something that has identified faulty wiring and is disconnecting the power to protect you. RCD's measure in-balanced currents between the live and neutral, your thoughts about surges and proximity of the RCD to the transformer, if valid would make products such as RCD sockets a bit of a non-starter.  https://www.screwfix.com/p/british-general-13a-2-gang-rcd-switched-plug-socket-metal-clad/4714p#_=p

Doc H. 

 

[Murdoch]

Have you got any test equipment?

Has anything recently been changed in the house / electrics / fuseboard?

Randomly changing things is not advised .....................

 

[Evans Electric]

Check where the  spur neutral is connected  .  It can easily get connected to the wrong neutral bar .  

It MUST be the neutral bar that controls the relavent MCB  .  

Almost certainly this is the solution .

These  boards generally have  three neutral bars ....the normal incoming neutral bar ......the neutral bar for RCD  1  ....the neutral bar for RCD 2 .         If the live is on the RCD1 side , your neutral could be  in the RCD2 bar ..or .the incoming neutral bar . 

Don't hesitate to come  back if its not the case .

Just to add to that ,  your socket may be wrongly connected  , the earth could be in the Neutral terminal  etc .  

 

[Doc Hudson]

Just to add to that ,  your socket may be wrongly connected  , the earth could be in the Neutral terminal  etc .  

While this can be a cause of RCD problems, in the OP's case he did say his fault could trip either RCD, not just the same one all the time. A socket problem would only trip one RCD, Whereas crossed neutral bars can be a pot luck who trips first gamble.

Doc H.

 

[Fluffy]

Thank you to everyone who answered. You were correct in assuming it was a wrongly connected neutral. It's back in the right hole and all's well!

thanks again!

 

[Doc Hudson]

Thanks for reporting back your findings, it is easily done popping a wire into the wrong terminal. Is your router & wifi all working good now as well?

Doc H.

 

[Fluffy]

All working fine and I don't have a cable running under the hallway rug to the socket on the opposite wall anymore. Thanks again.