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Posted By Topic: 2 core lighting cable

Jan 21 2014 07:18

Hi please don\'t crusify me for asking but, I have been asked to replace a domestic fuse board. However the lighting circuits are wired in 2 core with no earth at the lights or switches. So I am legal, do they need to be re-wired if I touch the fuse board or can I run a seperate earth to the lights & switches or can I leave the switches with 2 core? There will be RCD protection once the fuse board in replaced. I would prefer to re-wire but the customer wants to do the minium as he is on selling the property.

Jan 21 2014 08:34

When replacing a switchboard, there is no requirement to alter or upgrade the subcircuits fed from it, nor the mains / submains feeding it.

When replacing all of the circuit protection on a switchboard, you do have to fit RCD protection [].
But that doesn\'t man you have to provide protective earthing for subcircuits that don\'t already have it .
If you alter a subcircuit, especially by adding one or more points, then fault protection must be in place[ & 2.4.2], and all lighting points must have a PEC [5.4.3].
But those rules don\'t apply to replacing a fitting (switchboard). While RCD alone is not recognised as providing compliant fault protection, it is safer than not having any.

If you do add PECs for lighting, they can be separate from the live conductors - no need to re-wire - but minimum size applies to separate PECs [Table 5.1]


Jan 21 2014 09:33

Thanks for the reply. I didn\'t realise you could just upgrade the switchboard and leave circuits as they are. If I wanted to add an earth wire to the lighting points can I leave the switches as I don\'t think they are classed as a \"lighting point\". Also is there a refresher course you know about that covers new amendments etc. I don\'t do much domestic so would be good to get up to speed.

Jan 21 2014 10:34

Correct, a switch is not a lighting point, so for instance if a new point is added to an existing circuit the PEC only needs to go to the new fitting, not the switch, and not the other existing fittings.

Certainly adding the PECs will be a far better safety outcome than just the switchboard replacement with RCDs. But it\'s optional.


Jan 21 2014 10:48

Thanks again AlecK, do you know of a refresher course I could attend, I am in Auckland? Do you also know where I purchase an upto date wiring rules/standards with all the current ammendments?

Jan 21 2014 11:18

Ron (the host) runs refresher courses in Auckland. All the standards (up to date) are downloadable via the EWRB website. Log in via Real Me and then click across to the standards NZ website. The relevant standards should be freely downloadable from there.

If you dont have a real me logon ring 0800 661000 to get one :)

Jan 21 2014 14:04

1. So if I change a light fitting and discover it only has a 2 core cable it\'s optional to just leave it like that?
2. But if I add an additional light I need to run an earth cable to it?
3. Is this the same for Socket Outlets?

Jan 21 2014 15:43

That\'s several other completely different scenarios. The rules are different for each. And the rules can be different for the circuit wiring than for the fitting on the end of it.
AS/NZS 3000 allows repairs using original methods ; but all alterations and additions must comply with current requirements[1.9.3].
some people call that \"like-for-like\" replacement; and that\'s a useful concept.... but those words don\'t appear anywhere in the Rules.
That same fundamental difference between repairs an alterations is also in ESRs. Repair and replacement is Low Risk PEW needing only an ESC. Alteration isn\'t, and must have a CoC.

So as a repair you can replace a twin lighting cable with more twin. Or you can replace the light on the end. Or the switch, or anything else.
But a change is either installation or alteration. So if you add a new light, or move an existing one to a new location, all the current requirements for new work apply.

1. So if I change a light fitting and discover it only has a 2 core cable it\'s optional to just leave it like that?

Not necessarily. \"grandfather\" clauses like ESR 113 say an existing one can \"continue to be used\" provided it complied when installed, still complies with original Rules, and is not electrically unsafe.
But when you change it, the fitting is no longer \"continuing to be used\". You\'ve moved from \"continuing in service\" to doing a repair. The circuit wiring is continuing to be used, so can stay as is. But a change to the type of luminaire may mean old rules can\'t apply. And that change also alters the electrical characteristics of the circuit, the rules that let it remain may also no longer apply.

Whether you need to add a PEC depends on circumstances case by case. Changing readily accessible double insulated batten holder for a similar double-insulated fitting, no need for adding a PEC. But changing it for a brass-&-glass luminaire would require a PEC, because the new type of luminaire requires earthing (and probably would have required earthing under the original rules). Changing an out-of-reach fluo that was originally exempt from earthing, you generally wouldn\'t need to add PEC - but if someone has installed earthed metal within reach of it since it was installed, the original exemption no longer applies (it doesn\'t \"still comply\").
If you change a 100 W batten holder for a 1000w floodlight, rules about volt drop etc need to be considered as well as earthing.

It\'s sometimes open to argument, but bottom lines are everything you do must be safe, and you mustn\'t make things less safe than they were [ESR 13].

2. But if I add an additional light I need to run an earth cable to it?

Yes. This one is about the lighting point itself, regardless of what type of fitting you install. The original points remain under ESRs 113 etc, but the new one has to comply with current installation rules.

3. Is this the same for Socket Outlets?
No. LV Socket outlets have generally always needed a PEC. Clause 4.4.3 applies for new ones. Also, and other rules.