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Posted By Topic: Overhead wiring from bach to shed

Mar 06 2013 17:16


A customer has sent me some photos of a TPS cable ready to be taken from his bach to the shed and wants to run it overhead rather than underground, is this legal even in conduit or will a new 6mm2 2C NS cable have to be run with supports, conduit etc?

Mar 06 2013 19:46

TPS is fine supported by catenary.
Best to use polyester cord, but can use wire; plus cable ties

The Don
Mar 06 2013 19:51

As long as it is supported by a Catenary wire and is suitable for use in direct sunlight or protected then TPS is fine .
Read section 3.13 for more details

The Don
Mar 06 2013 19:54

:) snap Aleck must type faster than me LOL

Mar 06 2013 20:30

Speed does not beat accuracy.

this new keybpoeard has increased my typo rate by heaps

Trouble with catenaryn wire is need for earthing, whereas polyester (NOT nylon, nor polyethylene) has good UV resistance and doesn't need earthed.
But does stretch a bit, so have to allow for that.

other factor is use the current rating for "exposed to sun" (unless in Invercargill?)

Brian W
Mar 06 2013 21:58

Now THATS culturally insenstive Alec....

Mar 07 2013 08:20

And inaccurate... which as of course the point

Mar 07 2013 09:34

Alec, can you give me the reference requiring catenary wire to be earthed, please.

Mar 07 2013 09:56

clause 5.4.5

A catenary wire comes under "other conductive supports".

Catenary wire doesn't always need to be earthed - depends what it's attached to and where. But polyester never does.

The old ECP 28 had detailed provisions for catenary, and included the option of polyester cord. While the ECP has been superceded b the more general requirements of AS/NZS 3000; the concepts and advice are still valid.

Mar 07 2013 10:24

TY Alec

Mar 07 2013 10:56

No problem.

And I'll admit that reference isn't entirely obvious, but Standards don't like repetition so it's under earthing where it can apply to all types of aerial cabling, instead of under catenary only.

Maybe we should add the words "including catenary wires" ? That would mean it gets a reference in the index.

I reckon the ECP was better than the current rule, but to get a good NZ idea adopted you have to convince (most of) the 7 States of Oz. And even then some of them just dig their toes in - NSW still won't accept ACS on building sites. And apparently some won't accept solid 1 mm2 as a PEC in a TPS T&E or 3&E cable.


Aug 26 2017 09:56

Does a catinery wire need to be earthed if TPS is run through conduit?

Aug 26 2017 13:46

The question to answer is the catenary wire liable to become alive, TPS cable in conduit it is very unlikely that the catenary wire supporting the conduit would make contacts with the live conductors of the TPS cable inside the conduit.

Aug 26 2017 17:14

You'd be better to actually run the cord through HD solar conduit as well as the TPS to support both.
Cant see TPS, particularly the cable ties lasting 20 years in the sun.

Aug 27 2017 20:31

I had an interesting discussion with general cables recently re UV stable TPS, had to price to replace a fair few white TPS cables run open and exposed to the sun on roof mounted trays .. the upshot was, white TPS 100% not uv stable so should not be installed in direct sunlight.. Black circular TPS not UV stable so should not be installed in direct sunlight but would better stand up to the Sun. either way General cables would not guarantee the performance of the cables... ended up pricing with a firstflex uv stable orange sheath cable which would result in the outer orange sheath being somewhat bleached by the sun without any deterioration to the cable...