Possible electric fault following rewire

[Harry38271]

Hello all,

We've had a rewire and our electrican is currently away on holiday so we're unable to ask them for advice.

Please can I ask for your help with the fault. We had a full rewire including new consumer unit in the property and LED downlights installed (integrated slim line led variant).

We have light switches in the kitchen and utility (BG Nexus Brushed Steel look) which give a tingly sensation when we use them or touch the faceplate itself, but only when we're barefoot (tile floor above conrete). Would I be correct in saying there's a fault with the ground, and could it likely affect the other switches also, or the whole consumer unit?

 

[littlespark]

Is it an instant crack, or a more sustained tingly feeling?
Is it every time it’s touched?
Is it every person or just certain people?

First of all, if the board has been done right, then all circuits including lighting will be protected by RCD or RCBO… which means any earth fault above 30mA will trip off the power. (If not sure, post photo of the new board, lid open showing the breakers, with any names and addresses stickers of contractor blanked off)

Saying that, those devices can go faulty, even when new, so test them using the button on them.


The usual reason for shocks off a light switch is static. The person gets charged up walking around the house on carpet, becomes insulated on the tiled floor, then “earths” themselves when they touch a metal switch, even the fixing screw on a plastic switch can be earthed through the metal back box.


You can sometimes get erroneous “ghost” voltages through capacitance, where cables run parallel close together, or electronic devices leaking electricity to earth…


Basically, there are a number of reasons, and not all can be pinpointed.

 

[Avo Mk8]

I don't have a BG metal faceplate switch to hand, but for the Click brand (the screwless clip-on faceplate) there is no electrical connection between the ground terminal on the switch and the metal faceplate. The faceplate is isolated.

If that is also true for BG, and assuming we are talking a "screwless" type, it could just be capacitive coupling from the wiring behind the switch.

 

[Harry38271]

Is it an instant crack, or a more sustained tingly feeling?
Is it every time it’s touched?
Is it every person or just certain people?

First of all, if the board has been done right, then all circuits including lighting will be protected by RCD or RCBO… which means any earth fault above 30mA will trip off the power. (If not sure, post photo of the new board, lid open showing the breakers, with any names and addresses stickers of contractor blanked off)

Saying that, those devices can go faulty, even when new, so test them using the button on them.


The usual reason for shocks off a light switch is static. The person gets charged up walking around the house on carpet, becomes insulated on the tiled floor, then “earths” themselves when they touch a metal switch, even the fixing screw on a plastic switch can be earthed through the metal back box.


You can sometimes get erroneous “ghost” voltages through capacitance, where cables run parallel close together, or electronic devices leaking electricity to earth…


Basically, there are a number of reasons, and not all can be pinpointed.

Hi littlespark, thanks for your prompt reply!

The issue happens when touching the faceplate, or the switch and screws. The light switches are BGNBS12 1 Gang 2 Way Light Switch - Nexus - Brushed Steel.

It's a sustained tingly feeling almost every time it's touched by different people. Only in the kitchen and utility, which are separate rooms but utility is an extension attached to the kitchen, both atop concrete floor on tiles, other rooms are wood flooring.

Sorry not sure of the protection on the consumer unit. Tested all and they all go off when we press the test button.

Please see attached pictures of the consumer unit and other connections. This is a three bedroom extended property with one utility and a separate sitting room extension via the lounge. We did have one of the breakers trip when we plugged an internet wifi extender into one of the power sockets in the extension but it seemed to work fine after. Please advise if the electrical installation doesn't seem suitable for the property type.

 

[westward10]

I suspect they are not effectively earthed.

 

[Harry38271]

I don't have a BG metal faceplate switch to hand, but for the Click brand (the screwless clip-on faceplate) there is no electrical connection between the ground terminal on the switch and the metal faceplate. The faceplate is isolated.

If that is also true for BG, and assuming we are talking a "screwless" type, it could just be capacitive coupling from the wiring behind the switch.

Hi Avo Mk8, also thanks to you for the prompt reply.

The switch is a BGNBS12 1 Gang 2 Way Light Switch - Nexus - Brushed Steel, I could turn all electrics off and try to get a picture of the connections if that helps?

Thank you,

 

[Harry38271]

I suspect they are not effectively earthed.

Hello westward10,

Thank you for the advice, please can I ask whether it's possible other light switches are poorly earthed aswell as we can only tell the issue with the kitchen and utility light switch when we are barefoot (on tile above concrete which I believe creates a ground between our body) but everywhere else in the house is wood flooring so is it likely they are not grounded properly and we still don't know about it? Is the most sensible solution to have another electrician have a look as our current is going to be away for a few weeks now.

 

[Avo Mk8]

I suspect they are not effectively earthed.

If they are like my Click ones, and you put the cpc in the earth terminal provided, grounding it in compliance with 'the regs' it does not ground the metallic faceplate, which is isolated.

 

[littlespark]

I have never heard of that make of consumer unit... but then, i live in the back end of nowhere... so not surprising.

Separate RCBO for each circuit, which is good.... and SPD included... Hasn't cut corners.... except for the missing blank.

Yes, you just need someone that can test between the faceplate and a known good earth.


Im wondering why RCBO didnt trip? Not enough current? 30mA ain't a lot.

 

[Avo Mk8]

Hi Avo Mk8, also thanks to you for the prompt reply.

The switch is a BGNBS12 1 Gang 2 Way Light Switch - Nexus - Brushed Steel, I could turn all electrics off and try to get a picture of the connections if that helps?

Thank you,

Ok, so I gather you switch has visible screw heads each side of the switch.
That means my post #3 was completely irrelevant. Sorry everyone.
As Westward10 said, it does seem as if they are not earthed properly.
Unless you are DIY confident to investigate (with the electricity off!) it would be worth finding someone to check this out.

 

[westward10]

I have never heard of that make of consumer unit... but then, i live in the back end of nowhere... so not surprising.

Separate RCBO for each circuit, which is good.... and SPD included... Hasn't cut corners.... except for the missing blank.

Yes, you just need someone that can test between the faceplate and a known good earth.


Im wondering why RCBO didnt trip? Not enough current? 30mA ain't a lot.

I suspect the SPD has been fudged in explaining the pi**ed main switch and the half space.

 

[SJD]

The photos of a Danson consumer unit with surge protection all show the SPD to the right of the main switch, which is what I'd expect. So with the SPD fitted to the left of the main switch, I'm wondering how the busbar connection is made from the main switch to the MCBs. Unless the SPD is some older type with a single L terminal at the bottom?