One light circuit is tripping the system. what to look for?

[G and J]

8 minutes ago, saveasteading said:

Yes that's the plan. I was hoping for such an obvious bit of damage so it's good news. I need advice now on an acceptable way of patching in a repair, eg the boxes.

They seem appropriate to me as I can fix them to the joist to avoid any trailing cable.

I did, including after the visitors left, taking multiple chargers with them.

 

 

So it still trips even after your dangerous escapade!  Which switch goes?

[joe90]

Why not cut out say 100mm of that damaged cable and temporarily connect using a junction box (you seem to have slack if you cut the corner) if the tripping still occurs you have proved this damage was not causing the problem. 

[andyscotland]

3 hours ago, saveasteading said:

I'm down this way, nearly France, but electricicles behave the same.

 

I guess maybe @SteamyTea was thinking regs might be different, but this is just BS7671 which applies UK wide (not France though 🤣).

 

3 hours ago, saveasteading said:

Good reminder. It was Wagos that the electrician didn't like. I had done cabling on another daughters old house and asked him to do the final connections but he replaced them all.

I will take advice from @ProDaveor  other experts if they would please advise.

 

I'm not sure why the electrician didn't like Wagos if they were in a proper containment (other than that some people don't like new things).

 

When installed per manufacturer's instructions in a wagobox they are certified for use even in a totally inaccessible location (unlike anything with screw terminals). And are very hard to get wrong (again unlike anything with screw terminals). They do need to be in a proper box to provide protection for the unsheathed cables and strain relief, among other things, and the cable tie to hold the box closed is also important.

 

I would definitely use a wagobox to repair that damaged section, ultimately even if it's not the cause - and it could well be - it needs to be repaired anyway.

 

Hard to see from the photos how far it is to the junction box, if it's not too far best/cheapest bet is probably just one wagobox and then replace the whole section to the junction box. Alternatively get 2 boxes and just splice in a short replacement section. Make sure the cable you use matches or exceeds the size of the existing (I'd assume 1.5mm² will be fine, but check).

 

Unless you have a spare bit of suitable old cable lying around for the repair you are going to have different core colours in the replacement section. Old red = Brown, Old black = Blue. You should therefore also have a label like this at the origin (you can make your own) - not that there's really any electricians out there who aren't well aware of the harmonised colours by now!

 

Technically speaking as this is a repair to the fixed wiring it is Minor Electrical Works and should be done by a competent person, properly tested (with calibrated test equipment) & documented.

[G and J]

How I’d attack it would be set by whether it’s the RCD or MCB that’s tripping. 
 

Either way might be time for a kinetic type switch. 

[FuerteStu]

1 minute ago, G and J said:

How I’d attack it would be set by whether it’s the RCD or MCB that’s tripping. 

Yep. 

 

And if it's an rcbo, the way it trips.. A pop or bang. 

 

Is it live to earth, or neutral to earth

[G and J]

I think @saveasteadingsaid it happens even when the bulb is removed, and I would assume the switch is in the live side, so it is highly likely to be the returning switched live to earth (I think it’s most likely to be within one cable rather than between cables). 
 

But assumptions are dangerous things when dealing with stuff put in years ago by unknown dudes. 

[FuerteStu]

5 minutes ago, G and J said:

I think @saveasteadingsaid it happens even when the bulb is removed, and I would assume the switch is in the live side, so it is highly likely to be the returning switched live to earth (I think it’s most likely to be within one cable rather than between cables). 
 

But assumptions are dangerous things when dealing with stuff put in years ago by unknown dudes. 

Unless there is no other load on that circuit. 

It could be neutral to earth, but without load the rcd doesn't trip as there is nothing to imbalance

[Onoff]

You might find this interesting. Some of that old twin and earth with the white sheath just seems to crumble

 

https://electrical.theiet.org/wiring-matters/years/2021/84-march-2021/estimating-the-age-of-an-electrical-installation/

 

A discussion too on here from years back:

 

 

[saveasteading]

I'm going shopping apparently. 

I'll read all that clever stuff later....thanks all. 

[saveasteading]

OK thanks team. 

I'm having a few days off the subject, with family visiting I have other priorities and don't want any unforeseen consequences of a job half done.

 

I'll still be dealing with other people's problems on BH  which is much easier.

[joe90]

6 hours ago, saveasteading said:

I'm having a few days off the subject, with family visiting

And fixing taps and creating art 😎

[saveasteading]

Sorted.

 

I replaced a section of that gnawed cable, being the least disruptive course of action.

 

It works.

 

Although I can't quite see it, I think the black cable is through to copper. The earth shows some corrosion, white spots not green for some reason.

 

Thus we surmise that water got in there, and was shorting earth to neutral. The red looks to be intact.

The only sign of water is the black staining, but a single well aimed drop would be enough.

It might have dried out and worked for a while but it is done now.

 

I'm going back up another day to look for a leak (it is tiles on sarking board). I will put some barrier over this area to shield the other blackened cable.

Also I noticed that the last electrician up there to connect a toilet fan had not put the insulation back. Someone else's job I suppose would be his view....they are like that here.

 

I'm putting a plumbing query on a new post.

[Alan Ambrose]

Maybe there's a way of covering the cables with SS mesh or tube or something to encourage the blighters to gnaw on something else?

[saveasteading]

4 minutes ago, Alan Ambrose said:

covering the cables with SS mesh or tube or something to

There must be 200m of cable up there. I will cover this area though as it clearly appeals. Expanded metal is a good idea.

 

We can hear scurrying in the attic today, but the bait is going uneaten. Maybe there is plenty of food outside and they just come for the warmth and to multiply. At least they will not eat cable before the blue wheat.

[SteamyTea]

7 minutes ago, saveasteading said:

but the bait is going uneaten

The bait in our traps at work (pest control is a legal requirement) often seems untouched. We do find the odd 'dopey' mouse that you can pick up by hand, so must have been licked/nibbled.

 

Our biggest pest is a magpie. Stole my sandwich. It comes in the building and pecks at the food waste bin.

Not allowed to kill those I think.

 

There is a case, on a new build, for fitting steel cable conduit. Then let the sparky pull the cables through. May work out cheaper overall.

Edited December 29, 2024 by SteamyTea

[joe90]

10 minutes ago, SteamyTea said:

There is a case, on a new build, for fitting steel cable conduit. Then let the sparky pull the cables through. May work out cheaper overall.

Surely a new build will be pest free as if it’s air tight it will be pest tight? 

[SteamyTea]

4 minutes ago, joe90 said:

Surely a new build will be pest free as if it’s air tight it will be pest tight? 

Pest are really down to the food hygiene practices of the owners. Those vermin will find a way in to steal your crackers.

 

Useless Knowledge: Rats dislike potatoes, so chip shops are very really bothered by them (they like fish and burgers).

[ProDave]

8 minutes ago, joe90 said:

Surely a new build will be pest free as if it’s air tight it will be pest tight? 

Yes ours is.  Only one mouse in the house in 6 years, and that was through a partly open velux window.

 

The last house, they always got into the loft.  The ridiculous practice of a cold ventilated roof with the mandatory vents large enough for a mouse means that is inevitable.   And why I am a huge fan of a warm roof design with all insulation and air tightness following the roof line.

[joe90]

1 hour ago, ProDave said:

And why I am a huge fan of a warm roof design with all insulation and air tightness following the roof line.

+1

[Onoff]

[saveasteading]

Thanks for the extensive research. You may stand down now,. I'd never heard of this but now see that there is lots of this stuff online.

I've put a bit of plastic over the area in question, then an extra layer of fibreglass, but will bear this stuff in mind.

In lockdown I had a mouse move into the car, in the channel below the windscreen.  Anti-Marten spray* would be the business

I hesitate to think what is in it that repels rodents.. 

 

Reminds me of trying to buy slug pellets in Spain. I asked for bolitas  para corocoles.

 

In UK think asking for pellets for snails would be understood.

But the guy just stared.   

'Contra corrocoles?'   ahhhhh si.

 

As I write I am told there is scrabbling in the flat roof area.  I can't spray in there. Maybe it needs a third type of poison nearby.

Otherwise it has to be traps with chocolate but yeugh, I'm squeamish with impaled mice.

 

[Onoff]

2 hours ago, saveasteading said:

Otherwise it has to be traps with chocolate but yeugh, I'm squeamish with impaled mice.

 

Poison then. Smell goes after a week or so...

[G and J]

6 hours ago, saveasteading said:

Thanks for the extensive research. You may stand down now,. I'd never heard of this but now see that there is lots of this stuff online.

I've put a bit of plastic over the area in question, then an extra layer of fibreglass, but will bear this stuff in mind.

In lockdown I had a mouse move into the car, in the channel below the windscreen.  Anti-Marten spray* would be the business

I hesitate to think what is in it that repels rodents.. 

 

Reminds me of trying to buy slug pellets in Spain. I asked for bolitas  para corocoles.

 

In UK think asking for pellets for snails would be understood.

But the guy just stared.   

'Contra corrocoles?'   ahhhhh si.

 

As I write I am told there is scrabbling in the flat roof area.  I can't spray in there. Maybe it needs a third type of poison nearby.

Otherwise it has to be traps with chocolate but yeugh, I'm squeamish with impaled mice.

 

An instant death is much more humane. And once you’ve handled enough of the buggers you get quite immune to it. 

[saveasteading]

4 hours ago, Onoff said:

Smell goes after a week or so...

Mice 3 days. Small rats 5 days. Longer but less awful in winter.