mix and match

[tom1]

started this job,

new cu,

underfloor heating

add some sockets

change down lights

cu, how much twin can you fit in, nice earthing terminals

the conduit is no being used so was planning on cutting it back, to fit the new cu, metal clad was suggested on here a while back, but if i can cut it out that would be best. what would be best for cutting it?

but on further investigation as the kitchen was ripped out, the wall cladding and celling riped out, the wireing is a combination of singles in the conduit and twin, and in places just singles coming out of adapterble box

the kitichen and utility ring is twin into the celing then singles in conduit then to a strip connector spuring 2 sets of 3 sockets,

the lights are similare with conduits to switches.

so disconect the spures from the ring and leave it be to feed the utility, brought a new kitchen ring in, and some 2.5 for the under floor heating which will be 2200w perhapes i should put this on with the kitichen ring?

lights are a straingt swap so just striped back the pvc to get at the cut back cpc and leave it at that.

now the cu change can i still cut back the conduit as parts of it in the house are in use, it will prob still be earthed via the back boxs

http://www.talk.electricianforum.co.uk/attachment.php?attachmentid=548&d=1269710022

 

[ProDave]

I don't understand exactly your question, but I would recommend a full rewire of that lot, or at least a lot of remedial work to put it right.

 

[a1spark]

Hi Tom.

it appears you have opened up a right can of worms here mate.

A P.i.R before starting the job would have been appropriate here, but of course its easy to say that with hinsight, although some Inspection Testing is necessary even now that work has commenced going by what is shown in your pics.

I would think A metallic consumer unit looks the best option if the conduits are still in use. If you do go for an insulated C.U. and the conduits are readilly accessible and exposed and /or are being used as the cpc then a seperate 4mm cpc will have to be run in to its nearest conduit box terminal.

 

[tom1]

can of worms is about right.

i still have the option of a second cu for the 2 new circuits,

would not like to leave it like that,

cpc has been run through the conduit, but who knows what has been connected and were, wont know untill the board has been pulled to bits,

so as the conduit has singles in parts of it its got to be earthed 4mm back to the board or metal clad

 

[steptoe]

remember you cant use a 951 clamp to earth the conduit,

we do lots of these on council refurbs and recommend total rewires on them all,

use 3core singles.

 

[tom1]

remember you cant use a 951 clamp to earth the conduit,we do lots of these on council refurbs and recommend total rewires on them all,

use 3core singles.

would be nice if you could,

is there another way of earthing it other than through a box

he will not change much now, house is decorated bar the kitchen, people never look at wireing or heating befor the go spend thousends on decor and flooring,

i pulled apart 30 amp mcb for the kitchen ring, 2 ring end to end 0.30

one cable that aprears to feed nothing, and 2.5 to garage and shead

 

[sellers]

If you want to cut the conduit mate then take cables out and get a grinder with a thin metal cutting disc. If cables can't come out take it very very steady and score round it, then hit it with a hammer to break at the score.

 

[tom1]

If you want to cut the conduit mate then take cables out and get a grinder with a thin metal cutting disc. If cables can't come out take it very very steady and score round it, then hit it with a hammer to break at the score.

no cable in it mate its all twin until you get under the floor then its mix and match, its like its been rewired and they have picked up some of the old singles to avoid running cable, or made use of the existing conduit and used singles

got some loose conduit out of the celing its hefty stuff

 

[Zeespark]

What about an earthing adaptor for conduit? looks almost like a standard coupler?

AndyGuinness

 

[tom1]

What about an earthing adaptor for conduit? looks almost like a standard coupler?AndyGuinness

like this mate

http://www.tlc-direct.co.uk/Products/MK9933.html

 

[Zeespark]

No one sec, will see if I can track it down for you.

AndyGuinness

 

[Lee321]

but if you've just cut the thread off all the conduits with your grinder headbangROTFWL

 

[tom1]

but if you've just cut the thread off all the conduits with your grinder headbangROTFWL

can you get compression fitings for conduit,

 

[Lee321]

can you get compression fitings for conduit,

yes but not seen a compression earthing adaptor

 

[tom1]

a coupler might work if it lets me shorten the conduit

 

[Lee321]

yes definately can get those. called knock on bush adaptors tho as a knock on coupler would be like a plastic coupler get me?

 

[a1spark]

Just a suggestion..........how about drilling the conduit fully through its diameter and then 4mm tap the hole .....long 4mm bolt ...followed by 2 x 4mm nuts locked together ,followed by washer..followed by crimped eylet lug [with 4mm cpc lead attached...followed by washer and another nut ?...hope that makes some sense

 

[steptoe]

Just a suggestion..........how about drilling the conduit fully through its diameter and then 4mm tap the hole .....long 4mm bolt ...followed by 2 x 4mm nuts locked together ,followed by washer..followed by crimped eylet lug [with 4mm cpc lead attached...followed by washer and another nut ?...hope that makes some sense

or simply a 3.7mm hole and tap for a 4mm bolt, lug it and all is well.

 

[Sidewinder]

or simply a 3.7mm hole and tap for a 4mm bolt, lug it and all is well.

3.3 actually Steps!

Yours would only give you a 0.15mm depth of thread, not much contact there and under mechanical load not sufficiently strong remembering the BRB requires connections to be mechanically robust. Also under possible fault conditions the contact CSA could be inadequate to conduct the fault current as the female thread form would be truncated, thus any contact would be with the peaks of the male thread, very small in CSA, however normally many in number, but in the wall of a conduit, perhaps not so many, could average out a 1 per mm thickness (APPROX.!)

Also with commercial mass produced screws such as roofing bolts, gutter bolts, brass box screws, pan heads, etc. the OD's are reduced to the minimum the standards allow as this makes them cheeper and easier to fit, they are not suitable for structural use thus they are not strength graded, nor made to close tolerances.

M4x0.7mm pitch you take the pitch from the OD 4-0.7 = 3.3mm which is the tapping drill for M4x0.7, which is the standard M4 coarse pitch range.

This also works for ANY metric thread as the thread depth is geometrically reltaed to the thread pitch in a constant ratio right across the ISO metric thread range, other ISO threads vary as they are defined in threads per inch rather than in pitch distance.

:innocent

:coat

 

[steptoe]

3.3 actually Steps! Yours would only give you a 0.15mm depth of thread, not much contact there and under mechanical load not sufficiently strong remembering the BRB requires connections to be mechanically robust. Also under possible fault conditions the contact CSA could be inadequate to conduct the fault current as the female thread form would be truncated, thus any contact would be with the peaks of the male thread, very small in CSA, however normally many in number, but in the wall of a conduit, perhaps not so many, could average out a 1 per mm thickness (APPROX.!)

Also with commercial mass produced screws such as roofing bolts, gutter bolts, brass box screws, pan heads, etc. the OD's are reduced to the minimum the standards allow as this makes them cheeper and easier to fit, they are not suitable for structural use thus they are not strength graded, nor made to close tolerances.

M4x0.7mm pitch you take the pitch from the OD 4-0.7 = 3.3mm which is the tapping drill for M4x0.7, which is the standard M4 coarse pitch range.

This also works for ANY metric thread as the thread depth is geometrically reltaed to the thread pitch in a constant ratio right across the ISO metric thread range, other ISO threads vary as they are defined in threads per inch rather than in pitch distance.

:innocent

:coat

:coat

you're right , of course,

you could prob just screw a 4mm bolt into a 3.7 hole without tapping it would be so loose.