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View Full Version : NZ standards for mains earth - connection required at premises or not?



Agent_24
08-08-2014, 02:11 PM
I was just reading an article in this month's Silicon Chip magazine about mains earth faults, which raised some questions about my own house wiring.


Recently, the water pipe in my house was replaced with a plastic one. At the time I assumed the house wiring was earthed through the old pipe and questioned the plumber on this. He was unsure and said I should consult an electrician, but he said he had not found any electrical connection to the old pipe at the time.

Not long after, an electrician was around to replace worn-out thermostats in the stove. I asked him about the earth connection and he said there was no need for one in the house because New Zealand uses the Multiple Earth Neutral system, and an earth connection is provided by the electricity company 'somewhere' outside the premises.

Admittedly the article I just read is written for Australian homes and regulations, but we always seem to be very close if not the same as Australia in terms of electrical codes, and there was definitely no mention of anyone NOT having an earth in their house, either via the water pipe or a separate earth rod (or more)


Should I have an earth connection at my house or was the electrician right and it is not really needed? Does anyone here know the answer?

R2x1
08-08-2014, 02:25 PM
One of the earth points in the Multiple Earth Neutral System is close to the entry point at your premises. Without it, it is possible to have some interesting effects. Wives surprised to find themselves doing vigorous dances while hanging the washing out can adopt radical positions regarding domestic disharmony.
Rest assured, if the dancing wife happens to be your mother-in-law, your mirth does nothing to defuse the situation.

wainuitech
08-08-2014, 02:29 PM
Section 4 Page 25 ( if this link works its a PDF) http://www.med.govt.nz/energysafety/documents/legislation-policy/electricity-act-regulations-codes/standards-and-codes-of-practice/NZECP%2051%202004%20New%20Zealand%20Electrical%20C ode%20of%20Practice%20for%20Homeowner%20Occupiers% 20Electrical%20Wiring%20Work%20in%20Domestic%20Ins tallations%20%20-%20Published%2027%20July%202004%20.pdf Dont know if its upto date / still current or not

Some other interesting comments on another forum http://www.electricalforum.co.nz/index.php?action=more_details&id=1382344019 Same question

pctek
08-08-2014, 04:53 PM
At the time I assumed the house wiring was earthed through the old pipe and questioned the plumber on this.

electrician said there was no need for one in the house because New Zealand uses the Multiple Earth Neutral system, and an earth connection is provided by the electricity company 'somewhere' outside the premises.
?
Wander round the house outside, you'll see a wire in the ground somewhere......that's the house earth.
Could be under it although mostly it's up against it on the outside....somewhere.

R2x1
08-08-2014, 05:10 PM
Without an earth, you may not have an earthly chance of getting a red cent out of your insurance claim. (Don't try that at home;) )

B.M.
08-08-2014, 05:37 PM
This what you're after?

5884

tweak'e
08-08-2014, 06:08 PM
its not an earth via the water pipe but rather you earth the water pipe in case there is a short and the cooper pipes become live, which makes life in the bathroom rather short and smoky.
it gets a little interesting with some plumbing being muitiple products. eg i have cooper pipe onto pvc pipes.

R2x1
08-08-2014, 07:04 PM
5885

Here's a copy of the relevant bit of the requirements for domestic premises earthing.
Worst case, if you don't comply the coroner may get a bit terse when you say ". . . but I thought . . ."

Agent_24
08-08-2014, 07:59 PM
So, it looks like there should be one, even if under normal circumstances it may not make a huge difference, assuming the neutral connection back to the pole doesn't fail. I guess I should have the situation looked at by someone other than the previous electrician...?


Wander round the house outside, you'll see a wire in the ground somewhere......that's the house earth.
Could be under it although mostly it's up against it on the outside....somewhere.

The house is rather old. I know what the earth rods look like, having seen them on other people's houses. I have never seen anything remotely resembling one around or under my house, ever. The plumber couldn't find one either nor any evidence of there being or having been a connection to the water pipe. I think the clowns who built the place probably didn't bother, which would not surprise me considering other stupid things that have been discovered over the years.

tweak'e
08-08-2014, 09:49 PM
........other stupid things that have been discovered over the years.
like mine LOL

pctek
09-08-2014, 08:41 AM
The house is rather old. I know what the earth rods look like, having seen them on other people's houses. I have never seen anything remotely resembling one around or under my house, ever. The plumber couldn't find one either nor any evidence of there being or having been a connection to the water pipe. I think the clowns who built the place probably didn't bother, which would not surprise me considering other stupid things that have been discovered over the years.

Hmmm......they can be hard to spot, sometimes they are buried under garden and weeds (because of time).
My old house down south had one, I found it behind some rocks one day.

This newish one, it was by the toilet pipe, hidden behind weeds when we came.

B.M.
09-08-2014, 10:09 AM
If it were me I’d get under the house and look for a single green wire and trace that.

Often they were placed close to an outside tap in the hope that the soil would be damper in that area.

Billy T
09-08-2014, 06:48 PM
its not an earth via the water pipe but rather you earth the water pipe in case there is a short and the cooper pipes become live, .

Ummm.........Sorry, not so tweak'e. Grounding to a waterpipe was/is to ensure that there was/is a reliable ground for fault currents, and the earth stake was a back-up in that instance, or a life-saver after waterpipes became largely plastic. The earth stake also has to lie outside the drip line of the house to ensure that it remains wet and low impedance. AFAIK they still use copper for HW pipes, or do they have high temperature PVC these days?

I recently checked (for other reasons) the electrical system of a house where the earth/ground stake was underneath the middle of the building and in bone-dry clay. The house had a distribution board only, and the main switchboard and metering was at least 150 metres away on the (rural) property boundary. For supply purposes it may well have functioned adequately as connected, but it was in breach of the regulations, was not a very safe situation, and should never have been certified.

The whole idea of the MEN system (multiple-earthed neutral) is to use the combined local network of grounded pipes to ensure that in the event of a phase-ground breakdown (anywhere in the supply and distribution system, adequate fault current can be guaranteed to flow so that fuses blow or circuit-breakers trip. When that wiring is deficient, people die, as has happened at least twice in the recent past when a phase-neutral transposition occurred, and the MEN connection was defective or incorrectly wired by an 'amateur electrician.' I also recall one much older case where nobody was injured, but after several hours a concrete slab got pretty hot from the current flowing through it (via reinforcing steel) after the pole connection was miswired by a linesman.

Cheers

Billy 8-{)

Poppa John
10-08-2014, 11:34 AM
Mmy suggestion as a RETIRED ELECTRICIAN.

"Stop mucking about & get it bloody checked out by a known registered electrician & get the electrical WOF from him".

In my time in Auckland we still had Power Board electrical inspectors who checked permits after work was done. Earthing was something they were very hot on. An earthing infringment was a serious thing & at worst the culprit was "Invited" to attend an interview in Wellington,m at his own expense, to explain himself.
There are no inspectors to do this now. Electricians are now "Self Regulated" & after doing a job are supposed to do a set of tests & issue an electrical WoF. One copy to the householder, onne to the Wgtn Officce & one for the sparkies records.
Part of an electricians 'licence to operate as an electrican, is to have an approved short course in resuscitatio, from St Johns. We didnt have that in my timme but it was volutary so I did it. The instructos said one thing thatI have never forgotton...A serious electric shock locks up the heart muscle. Unless it relaxes , CPR wont work. So make a fist & slam it into the persons chest where the heart is. Then do CPR. If you break a rib he will thank you later on if he lives. If he dosent laie he wont complain.
The worst electric shock is hand to hand across the chest. This has the same effect as a heart attack. Trust me....this is not a pleasant way to die! PJ

B.M.
10-08-2014, 03:11 PM
An oddity about this earth situation is I once read where more Plumbers had been electrocuted than Electricians. Seems most of them were caught whilst cutting a water pipe under a house.

I guess the water main was being used as an earth, as in tweaks photo, and the neutral had become disconnected between the meter box and the supply.

Anyway, as PJ says, get a decent electrician to check the house over and seeing it is quite old check what it has been wired out with. VIR (Vulcanised India Rubber) insulated wires are a fire hazard at best. ;)

Agent_24
10-08-2014, 03:28 PM
An oddity about this earth situation is I once read where more Plumbers had been electrocuted than Electricians. Seems most of them were caught whilst cutting a water pipe under a house.

I guess the water main was being used as an earth, as in tweaks photo, and the neutral had become disconnected between the meter box and the supply.

That's one of the things mentioned in the article. The return current ends up being split between the neutral to the pole and the on-premises ground, apparently. Some people assume (incorrectly) that the ground rod (or water pipe) at your house only carries current during a fault. Apparently this is not so.


Anyway, as PJ says, get a decent electrician to check the house over and seeing it is quite old check what it has been wired out with. VIR (Vulcanised India Rubber) insulated wires are a fire hazard at best. ;)

Will do. Though how do you know which ones are decent?!

Agent_24
18-08-2014, 02:07 PM
Hmmm......they can be hard to spot


If it were me Id get under the house and look for a single green wire and trace that.

Found it - decided to get right under the meter box and see if anything came down - no wonder I didn't see it before. Green? Yeah, with a few patches of verdigris... :lol:

Looks rather underrated, and assuming the connections haven't corroded, it's useless anyway now since the pipe no longer goes anywhere near the ground.

But at least it's got a strain relief coil, right? :waughh:

Poppa John
18-08-2014, 04:34 PM
Found it - decided to get right under the meter box and see if anything came down - no wonder I didn't see it before. Green? Yeah, with a few patches of verdigris... :lol:

Looks rather underrated, and assuming the connections haven't corroded, it's useless anyway now since the pipe no longer goes anywhere near the ground.

But at least it's got a strain relief coil, right? :waughh:

Totally useless now. The minimum length of iron water pipe used to be at least 25 feet underground or as wanted by the power board inspector. GET IT SORTED ASAP..If you really want a kick in the bum to do something ...tell your insurance company that your electrics are not safe & why!!!!!! PJ

PS. The earthing cable was 6mm but I always used 10mm. PJ

tweak'e
18-08-2014, 05:28 PM
if it all possible make the earth cable as straight as possible, lightning will go down it better. simple thing but it can save your house.

B.M.
19-08-2014, 12:18 PM
Found it - decided to get right under the meter box and see if anything came down - no wonder I didn't see it before. Green? Yeah, with a few patches of verdigris... :lol:

Looks rather underrated, and assuming the connections haven't corroded, it's useless anyway now since the pipe no longer goes anywhere near the ground.

But at least it's got a strain relief coil, right? :waughh:

Ohhhh dear, well don't get THIS (http://www.youtube.com/watch?v=XyuJhPDwhHM) guy to help. :crying :crying :crying