just curious why the bare earth wire in twin and earth cable is sheathed in electric fittings eg sockets?
why sheath earth wire?
- Thread starter squowse
- Start date
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Sheathed in electric what?
sorry - now edited
The wiring regulations require that it is both identified (514.3.1&2) and insulated (543.3.2).
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yes. presumably there is some logic behind the regulations? i mean it could be identified by it being bare. it's not like you get mixed up when you strip the end of a cable is it? also what benefit is there in it being insulated?
Interesting point for you Ding... I beleive those requirements came in with the 14th Edition in 1966... one of my lecturers back when I was at college was saying that in the few years after there were quite a few guys who didn't want to change and didn't use it... it seems refusal to work to the latest standards isn't a new thing
H
holmslaw
..
Bare or sleeved, you still get some tw@s using it as a live conductor..
Less likely to create a fault when some tw@ uses it as a live conductor?
with ref to this thread why do cable manufacturers not produce T&E with the earth already insulated just like the other conductors. i am sure i saw cable with a pre covered earth years ago
1) £
2) Maybe it's thought more likely you'll hit the cpc as well as a live when you put a screw into it?
3) £
2) Maybe it's thought more likely you'll hit the cpc as well as a live when you put a screw into it?
3) £
Try splicing T&E if the earth was pre insulated!!!!
You would cut one insulant or another!!!!!
PRACTICALITY
You would cut one insulant or another!!!!!
PRACTICALITY
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If you look at the electrochemical series Zinc (Zn) is -0.76 volt and Copper (Cu) is +0.34 volt giving total of 1.103 volts see http://www.chemguide.co.uk/physical/redoxeqia/ecs.html these are the main components in the Daniel cell which is used as a standard to measure voltage.
Zinc is dissolves and when a salt bridge is used copper is precipitated from solution. Back in 1967 when I took the first CSE it was a question in the science exam and I had never heard of a Daniel cell my teacher had missed it out of the syllabus only question I could not answer so not likely to forget. It is also a major problem with boats where copper coated anodes (Earth rods) are used on shore and zinc cathodes are welded onto the boats for catholic protection.
Having seen the results of crowded back boxes and bare earth cables I would say main reason to use sleeves is safety. As to why not produced as a cable with earth wire already covered well they are. NYY 600/1000V to VDE0271/0276 3 Core (blue, brown & Green/Yellow) see http://www.batt.co.uk/products/index.asp?area=2&p1=20&p2=140&p3=395 but as already pointed out it costs more than the twin and earth which replaced the old lead sheaved cable and was made to look the same but since the grey outer is now non conductive an earth wire had to be added. We are now returning to metal outer cable with 'Guardian' XLPE/Ali-Tube/LSZH 600/1000V 'ERA' Approved which complies with BS 8436 see http://www.batt.co.uk/products/index.asp?area=2&p1=20&p2=140&p3=394 and here the reason that the earth is not pre-insulated is so that down the whole length the earth core is able to contact the ali-tube so ensuring if any metal penetrates the cable the protection device will open.
It does seem to have taken a long time to realise the problems in removing the outer metal covering and to revert to the old ideas.
Eric
Zinc is dissolves and when a salt bridge is used copper is precipitated from solution. Back in 1967 when I took the first CSE it was a question in the science exam and I had never heard of a Daniel cell my teacher had missed it out of the syllabus only question I could not answer so not likely to forget. It is also a major problem with boats where copper coated anodes (Earth rods) are used on shore and zinc cathodes are welded onto the boats for catholic protection.
Having seen the results of crowded back boxes and bare earth cables I would say main reason to use sleeves is safety. As to why not produced as a cable with earth wire already covered well they are. NYY 600/1000V to VDE0271/0276 3 Core (blue, brown & Green/Yellow) see http://www.batt.co.uk/products/index.asp?area=2&p1=20&p2=140&p3=395 but as already pointed out it costs more than the twin and earth which replaced the old lead sheaved cable and was made to look the same but since the grey outer is now non conductive an earth wire had to be added. We are now returning to metal outer cable with 'Guardian' XLPE/Ali-Tube/LSZH 600/1000V 'ERA' Approved which complies with BS 8436 see http://www.batt.co.uk/products/index.asp?area=2&p1=20&p2=140&p3=394 and here the reason that the earth is not pre-insulated is so that down the whole length the earth core is able to contact the ali-tube so ensuring if any metal penetrates the cable the protection device will open.
It does seem to have taken a long time to realise the problems in removing the outer metal covering and to revert to the old ideas.
Eric
[quote="ericmark";p="1087679" are welded onto the boats for catholic protection.
Eric[/quote]
Bloody hell that's what the crazy nuns were on about!!!!!!!
Eric[/quote]
Bloody hell that's what the crazy nuns were on about!!!!!!!
H
holmslaw
..
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