Help on lighting circuit

[piz]

Hello all
I today went to a flat to change a 16mm back box to a 25 mm to fit a dimmer switch all looked ok until I removed the old back box and it was in a copper mineral insulated cable as I understand it I cant connect these 3/4 wires so do I tell the customer she needs a re wire
Expensive dimmer!!! cant isolate it or cap it so do I just leave the breaker off with a notice the cable is like a copper pipe with white chalky powder as the insulation

Help Please

 

[Mark.W]

I don't understand! Why can't you connect the wires? It's only MIMS cable...
I might be having a senior moment.....HELP!!

 

[Lou7]

can't you dig it out and put a gland,pot and seal on it?

or

MK Electric - Item Information

I'm sure they used to do a flush version.

 

[piz]

Hi every time you strip the ouside copper back a white mineral substance appears and then breaks when you seperate the cable example the live conductors will toutch the ouside copper which is the earth

I have never done one before is it a complicated job??

 

[Mark.W]

Ok so from what I gather there is no gland, pot and seal as Lou7 rightly suggested.
I'm afraid then the chances are 99% that cable will be buggered, as the white powder you are referring is called Magnesium Oxide which is hygroscopic meaning it soaks up moisture. Do a resistance test on the cable!

Also be sure not to ingest any of the powder, you will be sick for days!!

If you have never done one then walk away, it takes a lot of practice!!

 

[piz]

Ok Many thanks

 

[Mark.W]

No probs and Good Luck

 

[Lou7]

It's quite easy but you need a few special tools, did you take the pot off ? if not then the other end will probably be the same.

Anyway if you don't know someone with the tools you might be better off stripping it out and replace with t+e.


sorry Brightsparks you got in before me.

 

[ashrow]

Piz
Micc is a skill few modern day spark can do, like the others above say you need specialist tools and the right pots,glands etc for the micc being altered (some micc is imperial size which adds even more grief!)

Just to say, as a helpful word of warning.! when you look/price at jobs like this.......... Flats 1960's, churches,schools and some 60's fire alarms may likley be wired in micc. its not commonly used now but if in doubt visit the job and remove light switch etc to see before giving a quote (a pain up the butt for small jobs but it save the agro later)

Good luck

Ash

 

[Darkwood]

Some councils still require micc use in schools and other public buildings, just run two 10mm 4core supplies up a lift shaft recently have they stopped training apprentices how to use it now???

 

[montybaber]

apparently its no longer taught (or it wont be soon) I cant see why not

 

[piz]

Yeah your right
Spoke to a couple of sparks never seen it speak to the older ones they know all about it
Thanks all of you for your help she has gone for re-wire quote

 

[Mark.W]

Wow from a dimmer switch to a re-wire, nice work! Well done.

 

[captainconduit]

apprentices not taught on micc or pyro as fp200 cable more commonly used. Must admit id rather use fp200 for fire alarms but pyro should be taugh cant believe sparks not heard of pyro

 

[chocolate]

Colleges avoid using MICC due to the high expense. I would imagine that apprentices will rarely come into contact with it. Especially with T&E and FP200 and SWA being the main wiring types in most locations.