Anyone can fix an MICC cable leading to a light switch in my house (London, N6)?

[davesparks]

looks like there is just about enough cable there to make the ends off again and have an inch beyond the disc to put a Wago on. But has anybody ever jointed a conductor within a pot and sealed it up again? I think one would have to be very careful to avoid soldering flux wicking into the insulant and deflux thoroughly before filling with compound.

That's exactly what I was thinking when I asked for a pic inside the switch. dig the old compound out, solder some extensions on and re-seal. I'd be game for giving it a go if I had time.

It would take a lot of mauling to break an otherwise completely intact conductor.

I don't know what the size is but the smallest imperial size MICC I've worked with is pretty tiny and easily snappable

 

[freddo]

But has anybody ever jointed a conductor within a pot and sealed it up again? I think one would have to be very careful to avoid soldering flux wicking into the insulant and deflux thoroughly before filling with compound. But it might be possible, especially if one is prepared to go to the trouble of making a scarf joint in the conductor. Then again, not much room in a 5/8" seal if that is what they are.

Yes I have, I just took my time. Prepared the ends of the conductors with a needle file, the scarf was not much of an angle, and I'm sure if I did it again I'd get away with a butt joint as described in the handbook. I was also able to remove the pot for better access. The cable was coming down the wall so that helped with keeping flux away, I did also use a flux cleaner, mostly to prevent the flux causing future corrosion. I used a fairly powerful micro jet type torch to silver solder the joint and a small oxy/mapp torch to preheat the end of the cable to prevent it sinking all the heat away, roughly following the Pyrotenax cable handbook instructions for jointing cable ends. I also used one of those helping hands things to hold the ends during soldering, I was able to fix that to the wall using one of the switch box wall fixing holes. The repaired cable passed the insulation tests off the scale of the meter. I did unclip a fair section of the cable from the wood panelling to prevent the risk of hot cable burning the wood.

The main reason for repairing rather than replacing was because I got to use a blowtorch the bare cable was very neatly run with 2 others from the same switch, the cable run was very visible so a joint box wouldn't look good and accessing the other half of the cable for replacement would be impractical as it would damage the ornate plaster covings etc.

I'm not sure why the conductor broke, was called out because the light was flickering and when the switch was unscrewed from the backbox the conductor pulled out of the sleeve, broken at the tip of the stub cap. No sign of damage or corrosion, must have been weakened during installation. I did have the benefit of this cable being metric though so it was easy to find a replacement pot. I'm not too good at opening old pots carefully to be able to reclose them. The pot was fitted a little past the gland too so I could remove a bit of the sheath for a tight fit for the new pot.

Not a quick job, I don't get many chances to improve my skills with this sort of work to be able to do it faster. I wish I'd taken some photos.

 

[Dustydazzler]

Thanks for your reply. I'll contact you shortly.

Thanks for your reply. Very helpful input.

Just fir the record contrary to popular folk law I am not Delroy from Eastway

He is a good old sparks who happens to work in London area

 

[Lucien Nunes]

the scarf was not much of an angle, and I'm sure if I did it again I'd get away with a butt joint as described in the handbook. I was also able to remove the pot for better access. The cable was coming down the wall so that helped with keeping flux away, I did also use a flux cleaner, mostly to prevent the flux causing future corrosion. I used a fairly powerful micro jet type torch to silver solder the joint and a small oxy/mapp torch to preheat the end of the cable to prevent it sinking all the heat away,

I was thinking that a plain scarf would be best silver-soldered, but a soft-soldered joint might be equally satisfactory if bound with some 32SWG TC wire first. I'd probably want to support the conductor to file it, e.g. drill the right diameter hole in a small block of material e.g. hardwood and cut the angle on one end. Feed the conductor through the hole and file it flush with the block. If it had to be done in situ in the pot, one could do something similar with a little piece of tubing.

Perhaps one of those mini spot-welders for putting the inter-cell links on battery packs would make a good weld of this size? Would avoid the flux issues and make a very quick job of it.

Many decades ago, one of my mentors did some very crafty jointing to the leadouts of a valuable prewar CRT that had been in someone's garden for years and the leads had corroded off at the welds. There were tiny, weak stubs remaining in the pinch but he managed to get inside with some 26SWG and make successful joints, and the tube turned out to be a corker.

There is no writing of any kind on the black insulation of the conductors.

The fact that it is not emblazoned with 'STUB SLV' etc. hints at it being imperial

 

[Sparky5473]

The micc on the right hand side looks like it has some cuts to the outer copper sheath before it goes through the wall so I would think that the insulation resistance could be low

 

[Lucien Nunes]

I also wondered at first whether there were dings in it, but now I'm more inclined to think it's an artefact of the pic.

 

[davesparks]

I also wondered at first whether there were dings in it, but now I'm more inclined to think it's an artefact of the pic.

I reckon it's had an intimate encounter with the chisel used to dig the hole in the wall.

 

[Deleted member 148954]

That's exactly what I was thinking when I asked for a pic inside the switch. dig the old compound out, solder some extensions on and re-seal. I'd be game for giving it a go if I had time.


I don't know what the size is but the smallest imperial size MICC I've worked with is pretty tiny and easily snappable

Here are the pics of what's behind this switch. Hopefully they help figure out what could be done here. Thanks again for your help.

 

[Lucien Nunes]

It's a pity we can't see the seal discs clearly or exactly where within them the conductors have snapped. But scaling the size off the pic compared to the box and cable, I am increasingly convinced that they are 5/8" seals on imperial cable. If the existing seals can't be salvaged and re-used, metric pots can be fitted; it may be necessary to drill out the cable entry and solder to the sheath, according to the specific cable diameter.

@Eugene: Do you know what year the property was built / wired? Is the circuit protected by an RCD or RCBO? Could you tolerate the box being moved 5cm up the wall?

Slightly odd setup there, with two cores from one cable and one from the other going to each gang of the dimmer, but there are a number of reasons why that might have come about. Clearly some previous convictions with those bits of terminal block.

 

[Deleted member 148954]

It's a pity we can't see the seal discs clearly or exactly where within them the conductors have snapped. But scaling the size off the pic compared to the box and cable, I am increasingly convinced that they are 5/8" seals on imperial cable. If the existing seals can't be salvaged and re-used, metric pots can be fitted; it may be necessary to drill out the cable entry and solder to the sheath, according to the specific cable diameter.

@Eugene: Do you know what year the property was built / wired? Is the circuit protected by an RCD or RCBO? Could you tolerate the box being moved 5cm up the wall?

Slightly odd setup there, with two cores from one cable and one from the other going to each gang of the dimmer, but there are a number of reasons why that might have come about. Clearly some previous convictions with those bits of terminal block.

Thanks. The house was built sometime in the 1960s. Don't know about RCD or RCBO - there is a fuse box of course but that's all I know. Yes, the box can be moved 5cm up the wall.

 

[UNG]

Have never know MICC to be used domestically except as a sub main up a tenement building in Edinburgh.

Sometime around the I think late 50's / early 60's BICC produced the Octpus wiring system which was used for wiring flats I believe it had a central box and all the cables were terminated into it this was laid out on the shuttering and the cables laid out to there various positions before the concrete was poured. A friend of my mum worked at the BICC factory in Prescot terminating the ends on piece work and was paid something like 3d per end it doesn't sound a lot but they could terminate upto 20 ends per hour. I remember seeing the film at college back in the 70's and it was amazing how they did it

Around Prescot you quite often find the odd older house wired in MICC usually the owner or past owner worked at the MICC part of the factory or were a relative of someone who worked there

 

[ipf]

I

Sometime around the I think late 50's / early 60's BICC produced the Octpus wiring system which was used for wiring flats I believe it had a central box and all the cables were terminated into it this was laid out on the shuttering and the cables laid out to there various positions before the concrete was poured. A friend of my mum worked at the BICC factory in Prescot terminating the ends on piece work and was paid something like 3d per end it doesn't sound a lot but they could terminate upto 20 ends per hour. I remember seeing the film at college back in the 70's and it was amazing how they did it

A penny a minute, 5 bob an hour, eh?
Must have been in the fifties UNG, maybe early 60’s, though.
I remember the octopus, they used loads in 60’s high rise flats.

 

[ipf]

Why the insulated lugs with metal screws in the switch back box?

It's still not clear to me where, exactly, the wires have broken.

 

[7029 dave]

Never liked this type of MICC clamp switch box, they were always shallow not designed for dimmers etc.
The better way would of been to use full terminations Micc glands then pot and coupler and bush into a standard deeper box .

 

[ipf]

Never liked this type of MICC clamp switch box, they were always shallow not designed for dimmers etc.
The better way would of been to use full terminations Micc glands then pot and coupler and bush into a standard deeper box .

I agree.... but when that one was designed the best description of a household dimmer was a lamp getting towards the end of it's life.

 

[7029 dave]

I agree.... but when that one was designed the best description of a household dimmer was a lamp getting towards the end of it's life.

Never got on with them stupid clamp (on the pot) accessories. Used them once that was enough

 

[ipf]

Never got on with them stupid clamp (on the pot) accessories. Used them once that was enough

Hey up......look what I've found. A church attic littered with them.

Installed correctly, they had their uses, I suppose


.

 

[7029 dave]

Hey up......look what I've found. A church attic littered with them.

Installed correctly, they had their uses, I suppose


View attachment 101651.

View attachment 101650

Nah would look better with a glanded MICC and stop end box , more expensive but a quality job lol

 

[littlespark]

Orange pvc coated MICC…. Now that’s a proper job!

Fire alarms in red as well?

 

[Dustydazzler]

I am certain that Del used on of those pancake pyro boxes on a job when he had to repair a damage pyro cable is a garage