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

[saveasteading]

19 hours ago, FuerteStu said:

If its recent,

No It's been ok for 30 years....and nowhere near my recent overflowing header tank (resolved 3 weeks ago anyway). Also nobody has been near that area.

 

19 hours ago, FuerteStu said:

Moisture inside the switch, or fitting. 

The switch is well clear of any water source....the fitting I will check when I venture up. Tomorrow is always a good day for unpleasant things.

 

 

20 hours ago, FuerteStu said:

the lamp itself causing the trip.

Removed without benefit.

 

20 hours ago, andyscotland said:

to be sure I've understood: 

correct It is 30A.

 

20 hours ago, andyscotland said:

t's common for electronics (computers, LED drivers, smart stuff) to produce a small level of background leakage due to the way electronic transformers work.

As 4 family members have just left along with many chargers,  I've checked again but it still trips. Anyway, they would be on the sockets ring main not the lighting circuit.

 

Much confused though as 2 switches tripped at the same time. Isn't that like a rope or chain snapping in 2 places? surely one part breaks and the other doesn't?

DB3 the left switch, along with the red switch on the distribution board (or am I misremembering already and it was the adjacent black? )

 

I put some special food in the attic a week ago, and then more. There was scampering until 2 days ago.  There is no smell of rotting rodents but they may have gone elsewhere to be tidy. Mice smell 3 days, rats 5 days.

 

So tomorrow I will put on my new favourite wooly hat with lamp in front (highly recommended) and get up there. I believe I am checking the ceiling connection for damp or dead things, and the cable from light fitting to switch, looking for teeth marks????

[andyscotland]

38 minutes ago, saveasteading said:

 

correct It is 30A.

30 milliAmps I assume.

 

 

38 minutes ago, saveasteading said:

As 4 family members have just left along with many chargers,  I've checked again but it still trips. Anyway, they would be on the sockets ring main not the lighting circuit.

 

The thing is the RCD is across both the sockets and the lights so that would not necessarily matter. But if still tripping then sounds like that's not a factor.

38 minutes ago, saveasteading said:

 

Much confused though as 2 switches tripped at the same time. Isn't that like a rope or chain snapping in 2 places? surely one part breaks and the other doesn't?

DB3 the left switch, along with the red switch on the distribution board (or am I misremembering already and it was the adjacent black? )

 

The red switch is just a switch so it won't have been that. If it was caused by the light it should have been the RCD (the black one with a test button) on the right  of the board e.g. furthest from the red switch as that is the one that protects the half of the board with your lighting circuit breaker (the one that is switched off).

 

It is possible for 2 RCDs to trip simultaneously - the tripping current and time are both so low that they trip easily and fast. Opening the circuit is a mechanical action so it's rapid but not instant. So the downstream can detect a fault and start opening but the power remains connected for enough milliseconds that the upstream also sees the fault.

 

Ideally an installation would be designed to reduce the risk of this happening but it's not always possible (and even with the best designs can't be guaranteed in all circumstances).

 

38 minutes ago, saveasteading said:

 

I put some special food in the attic a week ago, and then more. There was scampering until 2 days ago.  There is no smell of rotting rodents but they may have gone elsewhere to be tidy. Mice smell 3 days, rats 5 days.

 

So tomorrow I will put on my new favourite wooly hat with lamp in front (highly recommended) and get up there. I believe I am checking the ceiling connection for damp or dead things, and the cable from light fitting to switch, looking for teeth marks????

 

Depending how your lighting is wired, I would also check any cable from the suspect lamp to the next fitting. And also look out for any junction boxes nearby and similarly check them for dead things/damp/visible damage.

 

Make sure you de-energise the circuit at the distribution board before you start poking around, especially as there is a chance of damaged/wet connections. And if there is anyone else home who might be tempted to turn circuit breakers on, tell them what you're doing.

[Onoff]

52 minutes ago, saveasteading said:

So tomorrow I will put on my new favourite wooly hat with lamp in front (highly recommended) and get up there. I believe I am checking the ceiling connection for damp or dead things, and the cable from light fitting to switch, looking for teeth marks????

 

For example:

 

 

 

Also junction boxes that haven't had the lids put on properly and have open cable entries. Mice can get through a hole the size of a pencil. You can get slugs, wasps etc in there too. 

[BotusBuild]

On 19/12/2024 at 19:59, Mattg4321 said:

Only if there was a fault between the switch and an earthed back box could it cause tripping.

 

On 19/12/2024 at 19:59, Mattg4321 said:

unless subjected to very high loads or extreme temperatures etc.

 

On 19/12/2024 at 19:59, Mattg4321 said:

If in a domestic property it’s unknown how long it will last in good conditions as the earliest examples from the 60’s are still in good condition.

So, in all the quoted examples above, there is a possibility, however low that might be. Ergo, these things should be tested for. And that testing can be carried out without specialist equipment.

Regarding the last point, I bought a 1980's built property in 1997 and had to have about 25% of the wiring replaced as the cable had hardened and cracked. Sometimes, you get shit materials and knowing the quality of the rest of the property I can believe this builder was get stuff from wherever they could as cheap as they could.

🫳🎤

[saveasteading]

52 minutes ago, andyscotland said:

should have been the RCD (the black one with a test button) on the right  of the board e.g. furthest from the red switch

Memory failed on the colour, but it was that side so was the left hand black one.

 

The switch to the right that is off may be confusing things  (The one  with the tag against it)  It is another matter altogether. An outside light circuit that pings in wet conditions. so it is turned off.

 

50 minutes ago, Onoff said:

For example:

Helpful. I would be looking for such, but why would that short?  Exposed wire but the top one is not touching or near any other conductor??

 

 

 

 

[Onoff]

15 minutes ago, saveasteading said:

The switch to the right that is off may be confusing things  (The one  with the tag against it)  It is another matter altogether. An outside light circuit that pings in wet conditions. so it is turned off.

 

That's a possibility. If the outside light fitting is wet you could be getting a neutral to earth fault irrespective of whether that breaker is switched off. 

 

Might be worth isolating that "wet" light altogether. 

[Mattg4321]

4 hours ago, BotusBuild said:

 

 

So, in all the quoted examples above, there is a possibility, however low that might be. Ergo, these things should be tested for. And that testing can be carried out without specialist equipment.

Regarding the last point, I bought a 1980's built property in 1997 and had to have about 25% of the wiring replaced as the cable had hardened and cracked. Sometimes, you get shit materials and knowing the quality of the rest of the property I can believe this builder was get stuff from wherever they could as cheap as they could.

🫳🎤

Depends if you like wasting your time or not I suppose. 
 

Chances of it being any of those things mentioned are pretty slim. I like to target the most likely thing first, before clutching at straws, but have already given advice earlier in the thread, that has been repeated by someone else on here.
 

Getting up in the loft with the circuit disconnected and inspecting the installation is free and requires no insulation resistance tester. 
 

However, it’s probably still best to get hold of some proper test equipment or an electrician as ‘bang testing’ isn’t really something to be advised. 

[andyscotland]

15 hours ago, saveasteading said:

Memory failed on the colour, but it was that side so was the left hand black one.

 

The switch to the right that is off may be confusing things  (The one  with the tag against it)  It is another matter altogether. An outside light circuit that pings in wet conditions. so it is turned off.

 

Ah, I'd misunderstood the original pic. So I assume the circuit that feeds the suspect light is also on the left hand half of the board? That would make sense.

 

15 hours ago, saveasteading said:

Helpful. I would be looking for such, but why would that short?  Exposed wire but the top one is not touching or near any other conductor??

Top one would be fairly unlikely to be causing this type of fault (but should obviously still be fixed, for safety). Bottom one would be a candidate as there is a copper pipe nearby and if the exposed neutral contacted that (or was bridged to it by moisture) that would be exactly the type of trip you're getting.

 

15 hours ago, Onoff said:

That's a possibility. If the outside light fitting is wet you could be getting a neutral to earth fault irrespective of whether that breaker is switched off. 

 

Might be worth isolating that "wet" light altogether. 

 

Worth checking, but equally if we have now established that's on the other half of the board to the RCD that tripped then it is probably not the culprit in this case.

[G and J]

I’m worried.  How long do we wait for @saveasteading to escape from the rodent ruled attic before someone brave and foolhardy dons a head torch to go in after them?

[saveasteading]

28 minutes ago, G and J said:

How long do we wait

I've thought (and been reminded) of  10 other things I have to do first.

Finish 'wordle and connections', compost heap, visit the big project, get cat food.....