RCD question

[efiste2]

are there any issues that a socket outlet wired very close to the main dis board could casue to the RCD protecting it.

Had a mate call saying one socket on his downstairs ring main was tripping the RCD whenever something was plugged into it. He is new to the house and tells me the socket looks like a new one so could have been replaced and looks to be correctly wired.

In my humble opinion i reckon the socket outlet is more than likely the problem, but he made a statement that got me thinking, "is the socket too near to the RCD protection in terms of cable length.

My understanding of an RCD is that its an out of balance device that if the flux generated in the core doesnt blance out between the L and N, it induces the smaller coil and trips the breaker, so the length of cable between the RCD and the outlet is not a problem.

Am on on the right lines here, or does his statement hold any water so to speak ?

 

[JohnW2]

are there any issues that a socket outlet wired very close to the main dis board could casue to the RCD protecting it.

I can't see why there should be.

My understanding of an RCD is that its an out of balance device that if the flux generated in the core doesnt blance out between the L and N, it induces the smaller coil and trips the breaker, so the length of cable between the RCD and the outlet is not a problem. Am on on the right lines here, or does his statement hold any water so to speak ?

Exactly - I don't think his argument "holds any water" at all.

This reminds me of the story I've told here before about the "Part P registered" electrician who told me that I needed to have an additional RCD installed close to a shower in my (large) house, because the appreciable length of the cable back to the RCD in the CU meant that "a fault current would have become too small to trip the RCD by the time it got back to the CU". He then got very abusive when I tried to educate him!

Kind Regards, John

 

[AndyPRK]

The neutral could be connected to the wrong bar.

 

[JohnW2]

The neutral could be connected to the wrong bar.

How could that result in RCD trips affecting just one socket on the ring circuit?

Kind Regards, John

 

[westie101]

Had a mate call saying one socket on his downstairs ring main was tripping the RCD whenever something was plugged into it.

Come on John! Socket near CU so possibly wired direct and as a spur from the fuse/MCB?

 

[JohnW2]

Come on John! Socket near CU so possibly wired direct and as a spur from the fuse/MCB?

OK, OK. maybe I'm too quick to believe what people write:

... one socket on his downstairs ring main ...

Whilst I have your attention, did you notice the question I slipped into another post earlier today, asking how DNO folk check/confirm the polarity of an incoming TN-C-S supply?

Kind Regards, John

 

[westie101]

Whilst I have your attention, did you notice the question I slipped into another post earlier today, asking how DNO folk check/confirm the polarity of an incoming TN-C-S supply?

Nope, just catching up after a couple of weeks holiday, which thread I'll reply in there

 

[JohnW2]

Whilst I have your attention, did you notice the question I slipped into another post earlier today, asking how DNO folk check/confirm the polarity of an incoming TN-C-S supply?

Nope, just catching up after a couple of weeks holiday, which thread I'll reply in there

this one (click here) (post at 10:59 this morning). Thanks.

Kind Regards, John

 

[deadshort]

are there any issues that a socket outlet wired very close to the main dis board could casue to the RCD protecting it.

Had a mate call saying one socket on his downstairs ring main was tripping the RCD whenever something was plugged into it. He is new to the house and tells me the socket looks like a new one so could have been replaced and looks to be correctly wired.

In my humble opinion i reckon the socket outlet is more than likely the problem, but he made a statement that got me thinking, "is the socket too near to the RCD protection in terms of cable length.

I would suggest a faulty socket? I have had sockets that have had picture frames fall off the wall on to them not damaging the outer case but the knock was enough to rattle the innards and caused poor connection on the neutral pin.

Kind Regards,

DS





My understanding of an RCD is that its an out of balance device that if the flux generated in the core doesnt blance out between the L and N, it induces the smaller coil and trips the breaker, so the length of cable between the RCD and the outlet is not a problem.

Am on on the right lines here, or does his statement hold any water so to speak ?

 

[JohnW2]

I would suggest a faulty socket? I have had sockets that have had picture frames fall off the wall on to them not damaging the outer case but the knock was enough to rattle the innards and caused poor connection on the neutral pin.

It is obviously possible that a damaged/faulty socket could be the problem, albeit the issue you mention (poor neutral pin connection) would not, in itself, be enough to cause an RCD to trip.

However, I must say that the recently proposed mechanism is more than possible. Although I didn't initially twig what was being suggested, since this socket is close to the CU. it's possible that it is not part of the ring but, rather has been wired as a spur directly from the CU, with the neutral connected to the wrong bar. That would cause the RCD to trip every time that one socket was loaded.

Kind Regards, John

 

[EFLImpudence]

It could just be wired with N & E reversed wherever it is.

 

[deadshort]

Sorry John, why would a poor neutral connection not be enough (in you opinion), cause the RCD to trip ?

Kind regards,

DS

 

[JohnW2]

It could just be wired with N & E reversed wherever it is.

Well, yes, that is also true.

Kind Regards, John

 

[JohnW2]

Sorry John, why would a poor neutral connection not be enough (in you opinion), cause the RCD to trip ?

I'm afraid that I have to bounce that one back to you, and ask why you think it would be enough to cause an RCD to trip. Apart from some very esoteric situations (sometimes discussed in relation to DP switching) an imbalance between L and N currents which would cause an RCD to trip can only arise if some current is finding a route (usually via CPCs) back to the CU other than via L or N conductors - what such route are you proposing as a result of a 'poor neutral connection'?

Kind Regards, John

 

[deadshort]

No. sorry - not playing your game.

Kind regards,

DS