Type B Fuse keeps popping

[JohnW2]

Yes that is what I meant, it blew twice so I replaced it with a MCB. I have lived here for around 18months and it never happened prior to the first time circa 3 months ago. There hasn't been any rodents or major work around the house.

Fair enough - but bear in mind that work does not have to be 'major' to result in a screw, nail or drill being put through a cable!

Thinking back when it has blown, there seemed to a popping noise coming from around a blanking plate, does this suggest anything?

Given that popping noises should not come from behind blanking plates, that would sound like a good place for an electrician to start his/her investigations!

Kind Regards, John

 

[PrenticeBoyofDerry]

Look all the recommendation previously, the fault is not going to go away without employing a skilled electrician that can do some inspection/testing on the circuit, the circuit will have to be split down, to eliminate or establish where the fault lies.
Has the fault ever occurred when all appliance are off load?

 

[JohnW2]

Look all the recommendation previously, the fault is not going to go away without employing a skilled electrician that can do some inspection/testing on the circuit, the circuit will have to be split down, to eliminate or establish where the fault lies.

Indeed, but since the intermittent problem seemingly only manifests itself once every few weeks, it is unfortunately quite probable that any testing done at a particular point in time will reveal no abnormalities, no matter how much the circuit is 'split up/down'. If that proves to be the case, I imagine that inspection is the only way forward and, unless a problem is found within one of the accessible accessories, how easy that will be will depend on how accessible for inspection the wiring is.

Kind Regards, John

 

[Taylortwocities]

You could do the following:

Turn off the MCB that trips
Remove the blanking cover where you heard the popping noise
Take a photo of the wiring behind the blanking plate. Make sure there's some decent light.

Maybe we can see something that is amiss.

But, if you are really unsure about taking this step, then get your sparkyperson in and point them at the popping site!

 

[PrenticeBoyofDerry]

Look all the recommendation previously, the fault is not going to go away without employing a skilled electrician that can do some inspection/testing on the circuit, the circuit will have to be split down, to eliminate or establish where the fault lies.

Indeed, but since the intermittent problem seemingly only manifests itself once every few weeks, it is unfortunately quite probable that any testing done at a particular point in time will reveal no abnormalities, no matter how much the circuit is 'split up/down'. If that proves to be the case, I imagine that inspection is the only way forward and, unless a problem is found within one of the accessible accessories, how easy that will be will depend on how accessible for inspection the wiring is.

Well the only other option would be to make the circuit redundant and install a new one! The OP will get nowhere without some investigative inspection and testing going on, it is as simple as that! Regardless of how long it will take to establish where the fault be! We are not magicians!

 

[ban-all-sheds]

Yes that is what I meant, it blew twice so I replaced it with a MCB.

It was blowing for a reason.

Just swapping it for an MCB to make it easier to reset was the wrong thing to do.

Thinking back when it has blown, there seemed to a popping noise coming from around a blanking plate, does this suggest anything?

It suggests looking behind the plate, with the power off, to see what's going on.

 

[hohingday]

Yes I know swapping in for a MCB does not fix the problem, but it does make it easier to diagnose rather than having to change a fuse every time.

So I've looked behind it and I can see whats wrong, one of the positive cables is broken (a screw from the other side which I didn't put in) and has been touching the earth cable.

Pics attached.

What do you guys think? Whats the best way to repair?

 

[ban-all-sheds]

one of the positive cables is broken (a screw from the other side which I didn't put in)

FYI - AC doesn't have positive and negative - those are line (usually called live) conductors, with the blacks being neutral.

What does the screw attach to the wall, and in what room? Are you lucky to be alive?

Can the location of that cable be determined from the other side, or is it in a safe zone given corners/ceilings/other accessories? [wiki]electrics%3Awalls[/wiki]

Whats the best way to repair?

Cut back the cables to before the damage, reterminate in new choc-block (one of those pieces is damaged), with enough earth sleeving to cover all of the bare conductor.

And remove that (*"^^%'#~/ screw!

 

[Iggifer]

Wasn't just touching the earth cable by the looks of it! You need to get that sorted ASAP.

If you can pull some sack through you can cut back to where it's not damaged and rejoin the cables. You also need to change the connector block on the lives as you can see the brass where it's been badly cut.

There also really should be a box in the wall containing all of those cables.

I would not turn that circuit back on until its made good

 

[hohingday]

Sorry that is what I meant about positive/live.

I have no idea what the screw attaches to, I can’t see the other side of it as it has been plastered over, but it is in the blue safe zone.

There looks to be just about enough slack, I’ll get some choc block connectors and replace all of them.

I am surprised this has only been happening in the last few months as the screw must have been here prior to me moving in, so at least 18 months+!

Thanks for the advice, warnings and help.

 

[Iggifer]

Sometimes these things happen, it's unfortunate but the cable was probably hit when the screw went in, and over time it's worked its vibrated/expanded/contracted to the point where it occasionally makes contact with the live and earth at the same time, and when it does it goes bang

 

[JohnD]

heat-shrink sleeving to reinstate the damaged insulation.

 

[ban-all-sheds]

heat-shrink sleeving to reinstate the damaged insulation.

Thank heavens you've been round there and established that what looks like damage to the conductors is nothing of the sort, and that the energy released in those fault events has not vaporised any copper at all, so all that is needed is to repair the insulation.

 

[securespark]

No its one of those old metal type CUs.

Surely you mean new metal type CUs?

 

[stillp]

And remove that (*"^^%'#~/ screw!

I have no idea what the screw attaches to, I can’t see the other side of it as it has been plastered over, but it is in the blue safe zone.

If you can't see the other end of the screw, at least cut it off flush with the wall and put something like a blob of silicone over it.