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835 posts

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  Reply # 732237 13-Dec-2012 19:46 Send private message


No - E-N should be bonded on *any* mains distribution board (in NZ), and if it's not, that's a serious problem.

Absolutely - never gamble with potential mains problems..

(always happy to be corrected - especially by a registered sparky!)


Ok as a registered sparky......the E-N SHOULD be bonded together  in the main board, this is called the 'MEN link' current regs state only 1 MEN link per installation, although is the past the reg's have stated that there should be a MEN link in every mainbard and sub board, with the advent of RCD's this now means that in order for them to work correclt you must only have 1 MEN link.


mjb

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  Reply # 732257 13-Dec-2012 20:23 Send private message

gregmcc: Ok as a registered sparky......the E-N SHOULD be bonded together  in the main board, this is called the 'MEN link' current regs state only 1 MEN link per installation, although is the past the reg's have stated that there should be a MEN link in every mainbard and sub board, with the advent of RCD's this now means that in order for them to work correclt you must only have 1 MEN link.



Right - but wouldn't it be true that if a subboard is not RCD protected, then it could also have an MEN link? As it only matters that there is not an MEN link after and RCD?

And thanks for the clarification on SHOULD - I was certainly under the impression that it's required now.




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  Reply # 732260 13-Dec-2012 20:34 Send private message

It's just easier to only have 1 MEN link, it eliminates annoying 'random' RCD trips and when you have a large industrial installation having mutiple MEN links can cause large circulating earth currents which can cause all kinds of problems with senstive instruments.

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  Reply # 732389 14-Dec-2012 09:23 Send private message

The point about the 1.5mm cable to the outhouse is moot.... the installation could have been done under any of the previous regs.... it's probably not worth flogging that dead horse

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  Reply # 732391 14-Dec-2012 09:26 Send private message

gregmcc:

No - E-N should be bonded on *any* mains distribution board (in NZ), and if it's not, that's a serious problem.

Absolutely - never gamble with potential mains problems..

(always happy to be corrected - especially by a registered sparky!)


Ok as a registered sparky......the E-N SHOULD be bonded together  in the main board, this is called the 'MEN link' current regs state only 1 MEN link per installation, although is the past the reg's have stated that there should be a MEN link in every mainbard and sub board, with the advent of RCD's this now means that in order for them to work correclt you must only have 1 MEN link.



One particular installation where you can end up with two MEN links would be a sub board that is fed with a live and neutral from a main board, but has its own driven earth locally (in other words no earth conductor from the main switchboard) - this would require another MEN link.



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  Reply # 732423 14-Dec-2012 10:27 Send private message

richms: If it is showing nothing on L-N and connected 2 pin devices are working in the outlet, the tester is is defiantly wrong.


I'm wondering if the indicators on the front are indicating something different to what we would intuitively think from their description, because based on L-E being lit and L-N not being lit, you would think that means that the socket would not function, however on the diagramatic description on the back it says that that combination means earth not connected.

For correct wiring, it says that we should expect L-E and L-N lit, but not N-L, and this is exactly what happens on 95% of the outlets in the house, leading me to suspect that the tester is correct



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  Reply # 732465 14-Dec-2012 11:05 Send private message

I eased up the screws holding the socket in question and shone a torch in there - yup only two wires connected to the socket, both black, and no sign of a third (earth) wire in the wall cavity (no flush box, was just screwed into wood panelling). Definitely getting the sparky around now, im starting to wonder if they even used mains cabling for that outlet or if it was just low voltage figure-8 cable!

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  Reply # 732479 14-Dec-2012 11:16 Send private message

nickb800: I eased up the screws holding the socket in question and shone a torch in there - yup only two wires connected to the socket, both black, and no sign of a third (earth) wire in the wall cavity (no flush box, was just screwed into wood panelling). Definitely getting the sparky around now, im starting to wonder if they even used mains cabling for that outlet or if it was just low voltage figure-8 cable!


Sounds like fun... electricians of previous decades are notorious for the number 8 fencing wire and "she'll be right" attitude.... you would not believe the things I have seen!

Good job checking it out, and yes, a good electrician is certainly needed at this point.

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  Reply # 732487 14-Dec-2012 11:25

Evilg:
Sounds like fun... electricians of previous decades are notorious for the number 8 fencing wire and "she'll be right" attitude.... you would not believe the things I have seen!



I don't think a real electrician would use 2 core for a power point. I do wonder though why so many light fittings were installed without an earth. It may have been legal at the time but how much would the saving in wire cost have been?

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  Reply # 732520 14-Dec-2012 12:04 Send private message

nickb800: I eased up the screws holding the socket in question and shone a torch in there - yup only two wires connected to the socket, both black, and no sign of a third (earth) wire in the wall cavity (no flush box, was just screwed into wood panelling). Definitely getting the sparky around now, im starting to wonder if they even used mains cabling for that outlet or if it was just low voltage figure-8 cable!


I'm starting to envision masking (if really bad) or electrical tape tapped on to a light circuit somewhere lol. That's a shocker, no pun intended.

Good idea testing your plugs. First thing I do when moving in to a new home, re-wire the phones, cut the power and make sure all the wires on sockets and light switches are nice and firmly anchored. Strip the one's gone green and reconnect them. There's a lot of old stuff almost literately hanging in there from days passed.

I'm not a reg' sparky but safety conscious after living through one house fire and seeing some real messy old wiring in some places.


edit: I'm also glad they changed the regs regarding MEN. Neutral rightly should not be allowed to flow through earth, especially if older wiring has a smaller earth than neutral. Where I am now, someone reversed neutral and earth on one socket and I blew a few power supplies until I realised I could fell around 85v AC off my satellite dish and the ground.



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  Reply # 732523 14-Dec-2012 12:11 Send private message

This reminds me of the absolute worst that I have seen: In the garage of a mates student flat, someone in the past had added four light fittings, connected with several short lengths of outdoor grade telephone cable (modern black sheath, gel filled, two twisted pairs inside) As the the cable lengths were too short, they were joined in several places with electrical tape, and these joins hung down to head level.

I dont know how the cable didnt melt with the current being put through it, even though it was only four light bulbs

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  Reply # 732530 14-Dec-2012 12:27 Send private message

nickb800: This reminds me of the absolute worst that I have seen: In the garage of a mates student flat, someone in the past had added four light fittings, connected with several short lengths of outdoor grade telephone cable (modern black sheath, gel filled, two twisted pairs inside) As the the cable lengths were too short, they were joined in several places with electrical tape, and these joins hung down to head level.

I dont know how the cable didnt melt with the current being put through it, even though it was only four light bulbs


That's nuts. I beat the wire was pretty hot though. It might have been the gel helping to dissipate the heat?

I ripped out a lot of fluro lighting in a shop at the start of the year. They masking tapped together the additional fittings, as in paper tape. It was well out of reach, and relatively low current but still.

The worst I saw was burned off ends on a cable where an outside lamp used to be. So out of curiosity put a multimeter on it and it was still live. It wouldn't even switch off. Checked the switch and it looked like a swiss army knife with the amount of twisted together other circuits coming off it.

But that was at least plastic. I hate the old clothed wiring stuff that's all brittle these days. They made that out of asbestos didn't they?





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  Reply # 732549 14-Dec-2012 13:11 Send private message

kiwirock:
nickb800: This reminds me of the absolute worst that I have seen: In the garage of a mates student flat, someone in the past had added four light fittings, connected with several short lengths of outdoor grade telephone cable (modern black sheath, gel filled, two twisted pairs inside) As the the cable lengths were too short, they were joined in several places with electrical tape, and these joins hung down to head level.

I dont know how the cable didnt melt with the current being put through it, even though it was only four light bulbs


That's nuts. I beat the wire was pretty hot though. It might have been the gel helping to dissipate the heat?

I ripped out a lot of fluro lighting in a shop at the start of the year. They masking tapped together the additional fittings, as in paper tape. It was well out of reach, and relatively low current but still.

The worst I saw was burned off ends on a cable where an outside lamp used to be. So out of curiosity put a multimeter on it and it was still live. It wouldn't even switch off. Checked the switch and it looked like a swiss army knife with the amount of twisted together other circuits coming off it.

But that was at least plastic. I hate the old clothed wiring stuff that's all brittle these days. They made that out of asbestos didn't they?




Gee thats scary, I cant understand how blase people can be about electrical work.

Havent worked with clothed wiring, but my old flat had ancient plastic insulated wiring that had gone brittle - really an accident waiting to happen

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  Reply # 732678 14-Dec-2012 17:39 Send private message

Evilg: The point about the 1.5mm cable to the outhouse is moot.... the installation could have been done under any of the previous regs.... it's probably not worth flogging that dead horse


Unlikely as this has been in the reg's since the 1960's, the house is a 1970's vintage.


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  Reply # 732681 14-Dec-2012 17:40 Send private message

nickb800:
richms: If it is showing nothing on L-N and connected 2 pin devices are working in the outlet, the tester is is defiantly wrong.


I'm wondering if the indicators on the front are indicating something different to what we would intuitively think from their description, because based on L-E being lit and L-N not being lit, you would think that means that the socket would not function, however on the diagramatic description on the back it says that that combination means earth not connected.

For correct wiring, it says that we should expect L-E and L-N lit, but not N-L, and this is exactly what happens on 95% of the outlets in the house, leading me to suspect that the tester is correct


Um... L-N is the same as N-L


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