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Posted By Topic: Earth at All Lighting Points

DibbyD
Nov 05 2019 11:40

I've noticed in residential installs that some tradesmen are cutting the earth core on lighting circuits supplying LED downlights (only using red/black cores)

Obviously its not unsafe, seeing as the lights are double insulated, but it does mean that there's no earth continuity at any point on the lighting circuit

Anyone know if this is a requirement?

(AS/NZS3000-2007, 5.4.3 seems to say that continuity is necessary, but does have an exception for 'ELV lighting points')
   

OctaneOutlaw
Nov 05 2019 12:10

5.4.3 says "A protective earthing conductor, connected to a terminal or suitably
insulated and enclosed, shall be provided at every lighting point, including
transformers supplying ELV lighting systems."

The ELV exception is too the actual fitting as in the LED supplied on the extra low voltage side but if you read above there still has to be "a protective earthing conductor, connected to a terminal or suitably
insulated and enclosed" at the "transformers supplying ELV lighting systems."

And by cutting them off there is not earth continuity at ever point, nor are they "connected to a terminal or suitably enclosed and insulated"
   

COYS1
Nov 05 2019 19:25

I have wondered about this in the past. The wiring rules state an earthing conductor, no mention of it having to be connected, although my guess is that the likely intention is that it is connected. Does this mean it should also be tested even if unused?
   

COYS1
Nov 05 2019 19:25

By connected I mean to the earth bar.
   

OctaneOutlaw
Nov 05 2019 19:54

Well I guess if it's not connected then it's not really a PEC it's just a green/yellow insulated conductor that's floating and performing no task

"1.4.79 Protective earthing conductor
A conductor, other than a main earthing conductor, connecting any
portion of the earthing system to the portion of the electrical
installation or electrical equipment required to be earthed, or to any
other portion of the earthing system."
   

OctaneOutlaw
Nov 05 2019 19:56

And yes I believe it should be tested, without testing it how can you know that it's connected properly

Just like any other PEC, we test it to confirm its continuity and that it'll do the job that is intended to do
   

COYS1
Nov 05 2019 20:39

I guess the point is for a double insulated fitting it is essentially just a green yellow cable serving no purpose. In all fairness I'm probably being a bit stubborn in my comments, best practice is to do as you say.
   

DougP
Nov 05 2019 22:06

It's quite simple.

5.4.3 tells you that a PEC must be provided at every (new installed) lighting point, weather it is required or not.

8.3.5.1 tells you that the PEC must be tested. The required results indicate that you must test it to the full length, as the test result must be consistent with the size and length of the conductor.
   

DougP
Nov 05 2019 22:07

*whether
damn autocarrot :(
   

AlecK
Nov 06 2019 08:14

Exactly. If the PEC isn't continuous - and tested - to the end of the run, then the work is non-compliant. Not necessarily unsafe (assuming all DI fittings), but non-compliant.

Connecting the G/Y conductor to the earth bar (and at intermediate points such as switches) means there's a PEC to the first lighting point after the switch. But unless it's connected - to the ongoing cable, if not to the control gear / luminaire - then there's no PEC at the other lighting points in the string.

Yes it can be a bit tricky making that connection, as so many luminaires / control gears don't allow for connection of PECs within the fitting. But it's not that hard, because PECs - and connections in them - don't need to be enclosed.


   

greensleeve
Nov 07 2019 21:02

Most of what I see lately is the PEC bent back and taped to the cable itself.

I put in a connector and tape it down.

AlecK I thought 5.4.3 states it had to be enclosed ie connector at minimum?
   

AlecK
Nov 07 2019 21:13

5.4.3 simply requires a PEC at each lighting point (with Exceptions). Nothing there requires enclosure; and PECs can be single insulated or even (in some cases)uninsulated.
   

OctaneOutlaw
Nov 08 2019 07:10

What about the fact it says "connected to a terminal or suitably enclosed and insulated"

I just take that to mean you can't just twist them and leave them uninsulated

At least have to get that single insulation level back on them etc

Not saying it's the only method but I always put a connector on them to satisfy this
   

AlecK
Nov 08 2019 10:07

Which is a choice: one of two options; so that if it's connected to a terminal - as it must be (except at last fitting on circuit branch) - then it doesn't need to be insulated or enclosed.
   

pluto
Nov 08 2019 16:41

I like the UK wiring rules (which are very close to the international IEC 60364 rules)

Which saya a earthing connection shall be run to and terminated at each lighting point.

That makes it very clear that the earthing conductor must be run to and connected at each lighting point.

Perhaps as/nzs 3000 should be further amended to take in this UK wiring rule requirement.


By the way all NZ Electrical Wiring Regulations (with some local changes to suit local practices) up to 2003 where based on the UK wiring rules (IEE latter IET rules) , until NZ joined with the Australian Wiring Rules which also follow the IEC rules except for some local changes to suit local practices.