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Posted By Topic: Eathing

WillJ
Feb 22 2019 17:56

Just after some advice/opinions

We are installed a new switchboard in a dry cleaner store, 250a supply, the only access is through the front which is right on the foot path, the other three sides are solid concrete walls with other shops on the other side

We need to upgrade the earth electrode as its seems to be currently on the copper water main

Just want to know how/where others would go about installing new electrodes ( our inspector has said he would like to see 3)
   

Sarmajor
Feb 22 2019 20:38

And his grounds for requiring 3 are based on what..

AS/NZS3000:2007 says you have to have an earth electrode. Nothing about how many.
   

WillJ
Feb 22 2019 20:57

He said one pin per 100a
Didn't want to get into a big discussion about it with him without all the relevant info, which I'm working on now

   

DougP
Feb 22 2019 21:25

Does "our inspector" work for a network? Maybe you should find another one...

What is the supply arrangement to the building? Individual point of supply or common with other tenancies? In some cases with common tenancies, there will be a shared earth at the main distribution board or transformer.

Another option could be using the slab reinforcing if that's possible?
   

WillJ
Feb 22 2019 21:36

No hes a private inspector and yes we may find another one for this job

No common services, has its own supply pillar out the front
   

Satobsat
Feb 23 2019 00:25

Just out of interest did he say anything about how far apart they should be? I worked on a mobile extrusion factory that had an 800A board in one end of a container and a transformer in the other end. The Network drove a very large single electrode, with a very large pile driver. Took all morning.
   

WillJ
Feb 23 2019 09:51

No he said nothing about spacing

Is it acceptable to core drill a hole through the concrete slab under the switchboard and drive the earth peg/s there?
   

DougP
Feb 23 2019 11:13

Connecting to the slab reinforcing would be more compliant than an electrode inside the building.
   

Satobsat
Feb 23 2019 11:21

AS/NZA 3000:2007 5.3.6.4 states location requirements to be external to the building and exposed to the weather, unless there are certain covers that maintain soil moisture. You probably want to check with the building engineers before just cutting a hole. Why not cut a larger hole outside on the footpath and install an earth stake inspection box like in the link? Only a small 16mm or 20mm hole through the concrete wall would then be required, obviously on a downward angle towards the exterior to prevent water entering the building envelope. A bit of conduit down the wall to the box and you have protected the electrode, clamp and MEC from mechanical damage and have no trip hazard for the public.
https://www.transnet.co.nz/shop/Pillars+%26+Pits/TUDS+-+Total+Underground+Distribution+System/Earth+Rod+Inspection+Boxes.html
   

WillJ
Feb 23 2019 12:38

Just seeing if there was a alternative to outside, the footpath has all the other services running along the front

Would be great if we could get to the slab reinforcing, but thats probably harder, and its a old building so who knows what kinda steel is down there
   

zl2aj
Feb 24 2019 11:43

Outside in the footpath is probably no longer part of the installation (road reserve). You would need permission from the council to put it there (Corridoor access request) and that would likely get declined.