Online assistance for electrical trade people Login  |  Register  |   Forgot Password
Assistance for electrical trade people
 

 

 

 


Click here to send Ron a pdf document for publication on this Topic

Documents must be less than 200k in pdf format

Posted By Topic: A couple of clarification questions..

DougP
Jan 29 2018 13:13

1. Room heaters. Specifically standard bathroom wall heaters with a pull cord.
- If the isolation is at the switchboard, does the pull cord switch comply for functional switching? 4.9.3(a)

2. Main earth stake.
Is the expensive protection tube a specific requirement? Or is it simply part of general cable protection requirement?
I can't see anywhere under earthing/main earth etc where any protection for the connection to the stake is required.
   

pluto
Jan 29 2018 13:45

DougP Jan 29 2018 13:13

Your question 1. Room heaters. Specifically standard bathroom wall heaters with a pull cord.
- If the isolation is at the switchboard, does the pull cord switch comply for functional switching? 4.9.3(a)
answer 1 YES

Your question 2. Main earth stake.
Is the expensive protection tube a specific requirement?
Answer 2 See 3000 clause 5.5.1.2 (a) The main earthing conductor to earth electrode connection has to be accessible.
Question 3
Or is it simply part of general cable protection requirement?

Answer 3
No see answer 2

   

DougP
Jan 29 2018 14:30

Thanks Pluto.
So 5.5.5.1(a) explains about the pit, but for above ground, do we look to 5.5.5.2 regarding protection?
The case in question is a stake that is against the wall with the connection above ground, but the final connection to the stake is not protected. Should it have a cover tube?

And as a follow up question, 5.5.5.3 regarding corrosion - in Australia, they spray the top of the stake and the clamp and cable with galv paint - but I've never seen anyone do that in NZ.
Any thoughts?
   

AlecK
Jan 29 2018 14:56

Yes 5.5.1.2 (c) requires protection of the connection.

That doesn't require a proprietary "toby"; but it does require something to reduce the chances of the connection being broken by disturbance.

Note the MEC must also be protected throughout it's length, the protection being suitable for the location, under Section 3.
-----------------------

And yes (d) requires that this connection be suitably corrosion-resistant. Specifically, 5.5.5.3 applies; ie when exposed to weather "will prevent the entry of moisture affecting the conductor".

It's long been common practice in NZ to use brass clamp connectors. Brass being an alloy of copper & zinc, one might expect it would be OK to connect copper wire to galvanised rod. But in fact copper & zinc are incompatible, and in presence of moisture the zinc separates out of the brass over time. There are many reports of old electrode connections that are significantly corroded. Of course everything was fine when originally installed & inspected, but time takes its toll.

So it is good practice to use an anticorrosion treatment - but needs to be done in a way that doesn't reduce the effectiveness of the connection. "Spray-galv" (applied after making the connection) will be better than nothing, but a compound specifically designed to avoid corrosion, keep moisture out, and not "glue" the parts together is preferable.