earth wire sizing

[tester11]

I have always used 1.5mm single earth when wiring sockets in a conduit system, a guy on site just now is saying it should be 2.5mm earth same as live amd neutral conductors, is this correct amd why would it change because u use conduit ??

 

[chrish_1977]

I don't think it has to be, but I think it might be best practice as its in singles, when I do singles I use all the same size

 

[Guest111]

If you read the regs the cpc should be a minimum of half the size of the phase conductor,ie a 1.5 earth on a 2.5 phase conductor,however I must admit having spent most of my life in industry we always used 2.5 for all three.

 

[Deleted member 26818]

The minimum CSA for a protective conductor that is not incorporated in a cable such as T&E is 2.5mm², if provided with mechanical protection, 4mm² if not provided with mechanical protection.
Regulation 543.1.1 ...
"If the protective conductor:
(iii) is not an integral part of a cable, or
(iv) is not formed by conduit, ducting or trunking, or
(v) is not contained in an enclosure formed by a wiring system,
the cross-sectional area shall not be less than 2.5mm² copper equivalent if protection against mechanical damage is provided, and 4mm² copper equivalent if mechanical protetion is not provided (see also Regulation 543.3.1)."

Not 100% sure what exactly an enclosure formed by a wiring system is?

 

[loop3]

@ spin. Containment. Cms.

 

[telectrix]

pc went loopy then'

agreed as to containment being enclosure . conduit/trunking. but not tray/basket as that's not enclosed.

 

[Deleted member 26818]

I can't see it meaning containment.
Containment would provide mechanical protection, and if mechanical protection is provided the minimum CSA is 2.5mm².
Parts (iii) - (v) allow the protective conductor to be smaller than 2.5mm².

 

[telectrix]

i read it as.. if the cpc is not iii,iv,or v, then the min. is 2.5mm if mechanically protected and 4mm if not.

 

[Deleted member 26818]

The last paragraph states the minimu CSA is 2.5mm² if provided with mechanical protection.
Other than mechanical protection, what does containment provide?

 

[telectrix]

true. another ambiguous reg. you could argue that sheathed singles are mechanically protected as opposed to normal single insulated singles. it's open to more than one interpretation.

 

[wade88]

CPC is 1.67 times smaller than line conductors in T&E cable. So whats the problem with using 1.5mm singles. Ask him if he wants any gravy with his beef.

 

[Stroppy]

because the regs say: "The minimum CSA for a protective conductor that is not incorporated in a cable such as T&E is 2.5mm²"

I presume the reason being that when incorporated in T&E the CPC is somewhat protected by being surrounded by the other conductors and the sheathing, whereas in singles in an enclosure all conductors have equal protection.

 

[monkeyelectric]

I use 2.5mm for all 3 for sockets and 1.5mm all 3 for lighting or 4mm all 3 for 32a socket radials, after that i start dropping earth size

 

[Deleted member 26818]

true. another ambiguous reg. you could argue that sheathed singles are mechanically protected as opposed to normal single insulated singles. it's open to more than one interpretation.

Very ambiguous.
I'm wondering whether it's a reference to busbar trunking?
The definition for a wiring system states: "An assembly made up of cable or busbars and parts which secure and, if necessary, enclose the cables or busbars."

 

[wade88]

because the regs say: "The minimum CSA for a protective conductor that is not incorporated in a cable such as T&E is 2.5mm²"

I presume the reason being that when incorporated in T&E the CPC is somewhat protected by being surrounded by the other conductors and the sheathing, whereas in singles in an enclosure all conductors have equal protection.

Regs smegs