Using rebar as earthing.

[scania164]

Seems like a good way of saving on supply earth sizes?
Opt for a TT with a ufer earth instead of a TN-S?

 

[Knobhead]

To be changed.

Care to elaborate?

 

[Rockingit]

OK, I'll bite..... genuinely curious now. On a recent install there was a largeish (3m DIA) hollow steel silo buried about 4m deep into the concrete/foundations as the former for a cellar. So I thinks 'bingo' - what a great way to lower my Zs values.....so I duly put a 10mm bond from it to the nearest sub board about 5m away. And the net result was barely any difference to the readings. So, did I go wrong somewhere in my assumptions, or is there some part of the plot I'm missing??

 

[malcolmsanford]

The clue here Rock is in the regs and regulation 542.2.3 and the word "embedded"

I'm not a civil engineers but as far as I can see to get a foundation you dig a huge hole in the ground, inside that hole you lay a wick load of steel ree-bar and then pour tons of concrete on it, so you get your "embedded" part.

Again I'm not also a chemical engineer but I know that the chemicals that are used in the curing process for the concrete acts like a "Benotite" and with a vast volume of this and the steel that is embedded, you do get great values at least as good as a TN-S value.

I can only think that your steel "Silo" was not embedded sufficiently into the fabric of the concrete/ree-bar to be making a good connection

As I said previously out here using this I have got values of under a ohm, the lowest I can remember was about 0.72.

 

[Marvo]

Maybe the silo was coated or insulated to prevent corrosion?

 

[Geoffsd]

The reg. (542.2.3 (v))does say the rebar should be welded.

Does that mean it can only be used if it is planned and intended to be used as an electrode?

 

[telectrix]

not too well up on the subject of rebar. more my style would be FUBAR. :shuriken:

 

[mayfair]

Someone pinched my job LOL.

 

[Engineer54]

The reg. (542.2.3 (v))does say the rebar should be welded.

Does that mean it can only be used if it is planned and intended to be used as an electrode?

I've yet too see any foundation slab re-bar installation that was welded!! Probably nor has the author's of that Reg, and why it states ''Should'' and not ''Must''!! ...lol

 

[Geoffsd]

The reg. doesn't say 'should' - that was me, sorry.


542.2.3 Suitable earth electrodes shall be used...

(v) Welded metal reinforcement of concrete (except pre-stressed concrete) embedded in the ground.