Repairing imperial mineral cable

[davesparks]

Hi are you still working with imperial micc. I have electricians saying to me just because of one strand of the micc cable has been cut that I need a new rearing job done. They say parts not available to reterminate imperial mic. This is for connection to light switch. You defo look like you know what you are doing. Where are you and can we chat please. Ime in Hertfordshire by the way. Thanks Andy.

Imperial MICC can be reterminated using metric parts, there is a conversion chart which shows which pots and seals are required.

You might have to shop around a bit to find an electrician who can do the job, but there are still a lot of us around.

 

[7029 dave]

Imperial MICC can be reterminated using metric parts, there is a conversion chart which shows which pots and seals are required.

You might have to shop around a bit to find an electrician who can do the job, but there are still a lot of us around.

MICC is classed as a specialised job these days, unbelievable it was once an everyday task for any Electrician back in the day.

 

[oscar21]

I've still got some pyro stuff in the shed, haven't touched it in years though.

 

[davesparks]

MICC is classed as a specialised job these days, unbelievable it was once an everyday task for any Electrician back in the day.

Unfortunately the price of it makes it hard to justify on a job these days, a 100m drum of 2l1.5 will set you back nearly £900 and a pack of 10 glands is easily £40.

I still work with it occasionally, usually repairs or small alterations/extensions to existing MICC installs.

 

[nicebutdim]

Unfortunately the price of it makes it hard to justify on a job these days, a 100m drum of 2l1.5 will set you back nearly £900 and a pack of 10 glands is easily £40.

I still work with it occasionally, usually repairs or small alterations/extensions to existing MICC installs.

Certain brands of pvc coated steel flexible conduit aren't much cheaper.

 

[davesparks]

Certain brands of pvc coated steel flexible conduit aren't much cheaper.

Wow, I rarely use any floppy conduit, which brand?

 

[nicebutdim]

Wow, I rarely use any floppy conduit, which brand?

Can't name brands, but prices vary wildly from wholesalers. Some stuff is reasonably cheap, but £45-£50/10m isn't uncommon.

 

[pc1966]

Wow, I rarely use any floppy conduit, which brand?

We have used this, I think we got it a bit cheaper elsewhere:

(1) x 64453710 & (10) x 55501340 | Lapp Flexible Contractor Pack Conduit, 27mm Nominal Diameter, Steel Spring Wire, Grey | RS

uk.rs-online.com

Works out at just over £30/m ouch!

At this point I'm sure folks are thinking "WTF why use that?" but we found it lasts outdoors when flexing, while most others we tried would split after a year or so, etc.

 

[nicebutdim]

We have used this, I think we got it a bit cheaper elsewhere:

(1) x 64453710 & (10) x 55501340 | Lapp Flexible Contractor Pack Conduit, 27mm Nominal Diameter, Steel Spring Wire, Grey | RS

uk.rs-online.com

Works out at just over £30/m ouch!

I use quite a bit of similar stuff, but at a much better price. The steel in that is more for support than protection.

 

[pc1966]

Unfortunately the price of it makes it hard to justify on a job these days

Yes, I would struggle to think of cases where MICC is going to be your go-to choice as the traditional fire alarm case is now almost always FP200 or similar. Off the top of my head:

• Churches and similar historic buildings where the bare copper would look the part, even if in reality the building pre-dated electricity by several centuries.
• Blast furnace and similar where operating at seriously elevated temperatures is needed.
• Nuclear sites (not just power stations, but some research or medical) where radiation tolerance is needed.
• Military situations where NEMP protection is needed.

Any other suggestions?

 

[7029 dave]

Yes, I would struggle to think of cases where MICC is going to be your go-to choice as the traditional fire alarm case is now almost always FP200 or similar. Off the top of my head:

• Churches and similar historic buildings where the bare copper would look the part, even if in reality the building pre-dated electricity by several centuries.
• Blast furnace and similar where operating at seriously elevated temperatures is needed.
• Nuclear sites (not just power stations, but some research or medical) where radiation tolerance is needed.
• Military situations where NEMP protection is needed.

Any other suggestions?

Petrol stations

 

[pc1966]

Petrol stations

Good call, that and refineries / chemical works might also come in the the list.

In fact any case where really high reliability is needed.

 

[ipf]

MICC is classed as a specialised job these days, unbelievable it was once an everyday task for any Electrician back in the day.

Right or wrong, that is because of the electrical trade in general and it's views regarding other cheaper and inferior methods of wiring being produced and introduced as replacements.
For the last 40 years we've been subject to so many alternatives. Ease for labour and pocket, being the main reasons why. Still nothing to rival it.
If nobody had ever seen or heard of the stuff and it suddenly came out on the market today, it would probably warrant it's own apprenticeship.

 

[ipf]

Paint mix areas, boiler house systems, glass fibre production areas, fire stations.

 

[Boonsy641]

Imperial MICC can be reterminated using metric parts, there is a conversion chart which shows which pots and seals are required.

You might have to shop around a bit to find an electrician who can do the job, but there are still a lot of us around.

You anywhere near Hertfordshire? I really don’t want to rewire the flat because of single strand....failing that where or how do I find the measurements of existing imperial pyro such that I can convert and get new termination kit... many thanks

 

[Boonsy641]

Imperial MICC can be reterminated using metric parts, there is a conversion chart which shows which pots and seals are required.

You might have to shop around a bit to find an electrician who can do the job, but there are still a lot of us around.

Sorry about my posts, I sound like a pining teenager.. having come across all you guys I am confident I can get micc imperial repaired.. i have an electrician coming around today but over the phone he says it’s a rewire job.. and not knowing I would have taken his word... mainly him suggesting because you cannot get termination kit for imperial these days. His words.. I don’t doubt his ability at all, but I do think he has perhaps used my lack of knowledge and worry over this to make it a larger job.. I just can’t believe that because 1 single strand of the micc cable has broken near the pot that it means rewiring the flats lights... I will take some photos of the MICC connection if ok and post them, if you all don’t mind I will then ask your advice on size of pots I needs etc (imperial to metric conversion).. I’ll get it all, and then I just need someone to do it.... thanks.. glad I found this thread

 

[littlespark]

There could be ways to solve your switch problem without working on the MICC.

Do you know which core is broken? Live? Switchwire?
Could you do away with the switch altogether and use a “quinetic” switch instead?


You don’t want an inexperienced electrician messibg with MICC. If this one thinks it can’t be done, he could make a hash of it.

Sorry to say, it’s definitely not a diy job

 

[Boonsy641]

There could be ways to solve your switch problem without working on the MICC.

Do you know which core is broken? Live? Switchwire?
Could you do away with the switch altogether and use a “quinetic” switch instead?


You don’t want an inexperienced electrician messibg with MICC. If this one thinks it can’t be done, he could make a hash of it.

Sorry to say, it’s definitely not a diy job

Oh totally agree. I have researched enough to see that I need someone who knows what they are doing that’s for sure. I see him in an hour so I’ll sound him out. The Quinetic switch sounds interesting I don’t know what that is but will research. I think the wire that broken is but the wire for the immediate light it operates. I think it is for the two lights that follow in bathroom and bedroom as they are not working because of it. As I say I think I can source a gland and pot and tool for that matter. Just need someone to do the job. I hate not knowing and really am in hands of professionals but don’t know if the advice they are offering is to benefit them or me. Hence I am pleased finding this forum and you guys. If you can offer any suggestions I would be very grateful. Having redecorated just and spent a fair amount getting the flat ready for sister. There’s not a lot of cash to pay for a rewire that’s for sure

 

[davesparks]

Could you do away with the switch altogether and use a “quinetic” switch instead?

Most flush MICC installs of that era I've worked on used shallow boxes which had the built in clamp to hold the pot. If that's the case here it would be quite a bit of work to get a deeper box in there to take anything other than a standard plateswitch.

 

[davesparks]

. I just can’t believe that because 1 single strand of the micc cable has broken near the pot that it means rewiring the flats lights..

It is always possible that this could be a symptom of a bigger issue and rewiring is necessary. But if it is a simple case of someone has done something to damage this one cable then it should be repairable.

. I will take some photos of the MICC connection if ok and post them, if you all don’t mind I will then ask your advice on size of pots I needs etc (imperial to metric conversion).

Yes, post up some clear pictures so we can see exactly what has happened and get an idea of what repair is required.

Is it the MICC cable which has been damaged or is it one individual conductor within the switch box that has been damaged?

Wherabouts are you?

 

[davesparks]

Yes, I would struggle to think of cases where MICC is going to be your go-to choice as the traditional fire alarm case is now almost always FP200 or similar. Off the top of my head:

• Churches and similar historic buildings where the bare copper would look the part, even if in reality the building pre-dated electricity by several centuries.
• Blast furnace and similar where operating at seriously elevated temperatures is needed.
• Nuclear sites (not just power stations, but some research or medical) where radiation tolerance is needed.
• Military situations where NEMP protection is needed.

Any other suggestions?

Licence conditions on some West end theatres still require it, or required it up until recently, which is why I'm still working with it semi-regularly.
Although with some of them it's more a case of in-house staff hanging on to old rules and refusing to keep up to date, some of them still have a fit if you dare to bring 2 phases within 6 feet of each other.

The natural history museum also specify it for all of the areas with exposed stonework. You can see some fairly recently installed MICC in there which has been done to a very low standard, nowhere near straight and no thought to aesthetics.

 

[Boonsy641]

Most flush MICC installs of that era I've worked on used shallow boxes which had the built in clamp to hold the pot. If that's the case here it would be quite a bit of work to get a deeper box in there to take anything other than a standard plateswitch.

Some photos of the switch and connection

 

[davesparks]

Some photos of the switch and connection

Do you have the front half of the pot clamp? I assume this circuit is currently isolated if the clamp is missing?

Wherabouts is the damage, it doesn't look like anything is broken as far as I can see.

 

[Boonsy641]

Do you have the front half of the pot clamp? I assume this circuit is currently isolated if the clamp is missing?

Wherabouts is the damage, it doesn't look like anything is broken as far as I can see.

If you mean the cover that goes over these two cables yes I do. I unscrewed the cover and this was what lay beneath. They are both 3 core, the right hand one you can only see two cores and the third basically snapped off so you only see two. I had an electrician around who seemed to know his stuff, I think. He said not enough left of R/H 3rd core to do anything with as too short. Said that pots etc can get online also said the cable would need to be stripped back about two foot as to ensure any moisture is taken account of. He said copper becomes brittle so no guarantee when he digs out two foot of pyro that he will be able to terminate as it may be too brittle to do so but that is a risk that I must consider. He said that it would be terminated if not brittle to a sealed junction box and then twin and earth to the light switch. The big concern was if the pyro was brittle and it could not be terminated it would definitely need a rewire. The core cable that came away was for feed to other lights in the circuit I.e. bathroom and 2nd bedroom. He said that pyro was encased by concrete and that would be a big job to trace. I guess the concern was the cable being potentially too brittle to terminate if cut back

 

[davesparks]

If you mean the cover that goes over these two cables yes I do.

Good, this clamp makes the earth connection to the copper cable and the circuit must not be energised without it fitted.

I unscrewed the cover and this was what lay beneath. They are both 3 core, the right hand one you can only see two cores and the third basically snapped off so you only see two.

I can't make out the 3rd core for either of them.
Has anyone said what that thrid core is being used for?

I had an electrician around who seemed to know his stuff, I think. He said not enough left of R/H 3rd core to do anything with as too short.

It is very hard to make a repair if it is snapped off at the pot, but not always impossible.

Said that pots etc can get online also said the cable would need to be stripped back about two foot as to ensure any moisture is taken account of.

Cutting back 2 feet is unnecessary, it will only need to be cut back enough to expose enough of the snapped off core to be able to join onto it.
Has anyone carried out any testing yet to see if the cable is in useable condition or not?

He said copper becomes brittle so no guarantee when he digs out two foot of pyro that he will be able to terminate as it may be too brittle to do so but that is a risk that I must consider.

The only real risk is that the cable may have corroded due to chemicals in the plaster. But it looks like it is plastic coated MICC which has just had the last inch or two removed, you can see the orange outer sheath on one of them.
The sheath will have protected the buried cable from corrosion.

 

[7029 dave]

I keep looking at the picture and it looks like 2L1, even with the wiring configuration N's connected together in back box ? Perm Live in Common S/L out ? But hey am not there if you say 3core okay.
Silly question I take it the light/ lights dont work?
Could be a 3L1 disc but have only potted 2core

 

[littlespark]

Is it just my eyes looking at a phone screen, but I count only 4 cores between the 2 cables. 2 into a connector and 2 into the switch.

If there is even a short stump of the broken core, can a small 5A connector be screwed on and extend the wire?

 

[LeeH]

I haven’t made pyro off since my AM2 circ 1999 but I’m sure I still could with little issue.

I know this is not in the exam anymore, but is it still taught at college?

 

[davesparks]

I keep looking at the picture and it looks like 2L1, even with the wiring configuration N's connected together in back box ? Perm Live in Common S/L out ? But hey am not there if you say 3core okay.
Silly question I take it the light/ lights dont work?
Could be a 3L1 disc but have only potted 2core

They look like wedge pots rather than the usual screw on pots, were they ever used on metric cable or were they older than that?

 

[7029 dave]

They look like wedge pots rather than the usual screw on pots, were they ever used on metric cable or were they older than that?

No idea , I do remember Pyrotenax's heatshrink pot/ seals but never used them.

 

[davesparks]

No idea , I do remember Pyrotenax's heatshrink pot/ seals but never used them.

I keep a few of the heatshrink seals for emergency, 1 size fits most, type repairs.

I got one of the wedge pot tools in a box of second hand tools a few years ago but have never used it or even found new wedge pots.

 

[7029 dave]

I keep a few of the heatshrink seals for emergency, 1 size fits most, type repairs.

I got one of the wedge pot tools in a box of second hand tools a few years ago but have never used it or even found new wedge pots.

Can you still buy them, struggled to find them got a pic to show other members if they haven't seen them before.

 

[davesparks]

Can you still buy them, struggled to find them got a pic to show other members if they haven't seen them before.

They aren't manufactured anymore.
I keep an eye out for new old stock appearing on ebay.

I've collected a stock of cable and fittings from various people clearing out their stores.

 

[Boonsy641]

Good, this clamp makes the earth connection to the copper cable and the circuit must not be energised without it fitted.


I can't make out the 3rd core for either of them.
Has anyone said what that thrid core is being used for?


It is very hard to make a repair if it is snapped off at the pot, but not always impossible.

Cutting back 2 feet is unnecessary, it will only need to be cut back enough to expose enough of the snapped off core to be able to join onto it.
Has anyone carried out any testing yet to see if the cable is in useable condition or not?


The only real risk is that the cable may have corroded due to chemicals in the plaster. But it looks like it is plastic coated MICC which has just had the last inch or two removed, you can see the orange outer sheath on one of them.
The sheath will have protected the buried cable from corrosion.

Hey Dave. Trying to attach further photo

They look like wedge pots rather than the usual screw on pots, were they ever used on metric cable or were they older than that?

hi dave struggling to get low resolution images attached due to size. Defo 3 core each cable physically counted hopefully attached will show. Please see right cable. If you zoom in you can see ehats left of small cable. Electrician that came around said that if was to reterminate then the cables may be brittle in which case may not be able to reterminate at all in which case it defo would mean rewiring. At the moment he says the cable that broke is not live but is the common core that goes to next light in the loop. It connects to light switch and feeds of the live that is already there. He says best bet is to run a new twin and earth from the circuit breaker to the light that isn’t working but that would mean conduit across ceiling as in these flats the ceiling is concrete. I really would like to reterminate the pyro but worried about it being brittle as he says and making it worse

 

[Boonsy641]

They look like wedge pots rather than the usual screw on pots, were they ever used on metric cable or were they older than that?

Dave please see pictures

 

[littlespark]

For the photos, what I do when I take a photo with my phone is to screenshot it, then crop the screenshot down to just the original photo.
On my iPhone, that brings the image size just low enough for the forum to accept.

Do you have a photo looking up into the seal side of the pot, showing where the core is broken?

I still think you might get enough of a stump of copper for a very small connector to fit on…. Even the Ideal push fit type, rather than a block connector.

 

[Boonsy641]

For the photos, what I do when I take a photo with my phone is to screenshot it, then crop the screenshot down to just the original photo.
On my iPhone, that brings the image size just low enough for the forum to accept.

Do you have a photo looking up into the seal side of the pot, showing where the core is broken?

I still think you might get enough of a stump of copper for a very small connector to fit on…. Even the Ideal push fit type, rather than a block connector.

Thanks. That works. Please see. Just see the stump

 

[Boonsy641]

For the photos, what I do when I take a photo with my phone is to screenshot it, then crop the screenshot down to just the original photo.
On my iPhone, that brings the image size just low enough for the forum to accept.

Do you have a photo looking up into the seal side of the pot, showing where the core is broken?

I still think you might get enough of a stump of copper for a very small connector to fit on…. Even the Ideal push fit type, rather than a block connector.

Can you recommend a connector? I’ll try it myself I think. Many thanks

 

[davesparks]

Defo 3 core each cable physically counted hopefully attached will show. Please see right cable. If you zoom in you can see ehats left of small cable.

Yes I can see it now, that is definately a challenge to repair but I see no reason why it would not be possible to repair that with relatively little further damage to the wall.

Electrician that came around said that if was to reterminate then the cables may be brittle in which case may not be able to reterminate at all in which case it defo would mean rewiring.

I very much doubt that the cable has become brittle, without outside influences causing it copper doesn't just degrade and become brittle.

At the moment he says the cable that broke is not live but is the common core that goes to next light in the loop.

OK, that makes a bit more sense now.


I think you have 2 possible options here.

1 repair the existing cable

2 repurpose the switched live (marked yellow) as a permanent live and then fit a wireless switch with a reviver at the light to replace the switched live. The wireless switch may have to go on a surface box mounted over the existing switch position.

 

[davesparks]

Can you recommend a connector? I’ll try it myself I think. Many thanks

The only connection you could make onto that is by, with great care, cutting the plastic stub back and soldering then heat-shrinking.

There's no mechanical connector I can think of that will make a good connection to that tiny stub

 

[ipf]

If there isn't enough cable to repair, take the switch up 6 inches, new box with knockouts, or as existing with earth clamps fitted, strip back and re terminate.
Need a decent, experienced spark, though.
High switch, but what's the cost?

 

[7029 dave]

How the hell did that 3rd core snap off

 

[7029 dave]

If there isn't enough cable to repair, take the switch up 6 inches, new box with knockouts, or as existing with earth clamps fitted, strip back and re terminate.
Need a decent, experienced spark, though.
High switch, but what's the cost?

With Gland couplers and bush would make it a tad lower

 

[nicebutdim]

I haven’t made pyro off since my AM2 circ 1999 but I’m sure I still could with little issue.

I know this is not in the exam anymore, but is it still taught at college?

Indeed it is, although few will ever get much experience of using it.

 

[Boonsy641]

Yes I can see it now, that is definately a challenge to repair but I see no reason why it would not be possible to repair that with relatively little further damage to the wall.


I very much doubt that the cable has become brittle, without outside influences causing it copper doesn't just degrade and become brittle.

OK, that makes a bit more sense now.


I think you have 2 possible options here.

1 repair the existing cable

2 repurpose the switched live (marked yellow) as a permanent live and then fit a wireless switch with a reviver at the light to replace the switched live. The wireless switch may have to go on a surface box mounted over the existing switch position.

Dave. Can you recommend a wireless switch. If repurposing the yellow cable to permanent live then that would provide power to bathroom and bedroom that is currently in darkness. Is that right? Forgive my naïve Rss but how would the witless switch be powered? And you mean mounting witless switch over the top of normal switch? Is this something an electrician would find challenging or easy? Many thanks. Really appreciate your help on this I truly do

 

[Boonsy641]

How the hell did that 3rd core snap off

I have my doubts but initial electrician came round due to flickering light and tightened cables but before he did so he opened a few of the light switches and on this one when he opened it he said the cable easily came away.

 

[Boonsy641]

If there isn't enough cable to repair, take the switch up 6 inches, new box with knockouts, or as existing with earth clamps fitted, strip back and re terminate.
Need a decent, experienced spark, though.
High switch, but what's the cost?

My issue it seems is getting someone who could do this. It’s totally beyond the electricians I have had around. (So far 3). They have suggested a rewrite and then trunking or lowering ceilings!! I am absolutely dumbstruck that a single core of a cable is broken and I have been told it could abe a rewire running into the thousands. I know I don’t know electrics but I can’t understand why this cannot be fixed. Are any of you guys available to fix this please. Or recommend someone who can? Last electrician came around and I used all your comments and he went quiet. I feel he expected me just to accept a rewire. Thanks everyone. You are the light in a dark bathroom and 2nd bedroom!!

 

[westward10]

As is #90 this can be done. Carefully cutting the stub back with a razor blade or very fine file then snap it away and solder, someone who has patience and a deft hand.

 

[davesparks]

I know I don’t know electrics but I can’t understand why this cannot be fixed.

This type of cable has fallen out of common use, it can be time consuming to work with and the skills needed to fix it are rarely found within the domestic sector. So most electrician's you find doing domestic work either don't want to work with it, don't know how to work with it or some won't even recognise what it is.

Are any of you guys available to fix this please.

Depends how long you can wait! My other half is in Stevenage so I'm often in the area but I am fully booked now for a few weeks.

 

[Boonsy641]

This type of cable has fallen out of common use, it can be time consuming to work with and the skills needed to fix it are rarely found within the domestic sector. So most electrician's you find doing domestic work either don't want to work with it, don't know how to work with it or some won't even recognise what it is.



Depends how long you can wait! My other half is in Stevenage so I'm often in the area but I am fully booked now for a few weeks.

All the good one are fully booked is the rule. It just says to me that those fully booked are worthwaiting for. Sorry to ask and I am humble asking. How confident are you that you can fix it ?(sorry Dave. Have to ask) hope you don’t mind. Ime in Hitchin by the way