requirements for tt earthing?

[thekingiam]

was looking at a tt cu and the main earth goes outside into a concrete driveway cable looks quite small, is the minimum cable size requirement the same as other earthing arangements?
if i do need to replace, would i need to provide inspection pit.
its being protected by a rcd,could i use rcd as means of isolation while changing cu?.
testing earthing arangement could i do earh loop test on my multimeter instead of having to buy electrode tester?

 

[telectrix]

conductor size 6mm unless buried, then it's 16mm. you can get a Ze reading with your multifunction tester. no need to measure Ra., and yes, you can use an RCD for safe isolation.

 

[thekingiam]

thank you telctrix for fast response where you find regulation for size out of interest?
i might as well ad inspection pit as needs replacing, will have to get kango out damn..

 

[telectrix]

my bad. table 54.1. 2.5mm if mechanically protected, i.e. in conduit, 16mm if buried direct.

edit: read 542.2.1 as regards eartrh electrodes.

 

[Top Cat]

my bad. table 54.1. 2.5mm if mechanically protected, i.e. in conduit, 16mm if buried direct.

edit: read 542.2.1 as regards eartrh electrodes.

???????

My bad, you bad, he bad!

Tel i know you's bad! :crazy:

 

[Guitarist]

On TT systems see OSG table 4.4(ii)

Protected or not protected against corrosion, but not buried - 4mm

Protected against corrosion, but buried - 16mm

 

[GLENNSPARK]

conductor size 6mm unless buried, then it's 16mm. you can get a Ze reading with your multifunction tester. no need to measure Ra., and yes, you can use an RCD for safe isolation.

this is where the OSG is misleading....look at the diagram for TT earthing arrangements....its clearly showing a 16mm CSA main earthing cable....is that a case of if in doubt?....if so its a bit contemptable isn`t it....

 

[Guitarist]

this is where the OSG is misleading....look at the diagram for TT earthing arrangements....its clearly showing a 16mm CSA main earthing cable....is that a case of if in doubt?....if so its a bit contemptable isn`t it....

I'm actually trying to find where the regs and OSG agree here. Clearly states 4mm in OSG but can't find any reference in the regs to anything other than 2.5mm, 16mm & 25mm

 

[Engineer54]

If you do need to replace the earth conductor from the earth rod, then Yes, ...it would be very advisable to provide a flush to driveway inspection earth pit!!! ...lol!!

 

[GLENNSPARK]

If you do need to replace the earth conductor from the earth rod, then Yes, ...it would be very advisable to provide a flush to driveway inspection earth pit!!! ...lol!!

folk wont pay for em though eng as they see it as an unneccessary expense....protecting the earth path to your supply couldn`t be more necessary in my eyes..lol...

 

[Engineer54]

folk wont pay for em though eng as they see it as an unnecessary expense....protecting the earth path to your supply couldn't be more necessary in my eyes..lol...

Also a means of keeping the earth around the rod wet, damp, moist!!!! Not to mention a means of applying conditioning chemicals etc!! The worst thing you can do to an earth electrode is is cover it with an impermeable covering, the dam thing will dry out, especially with the UK's love of 1m rods, that are rarely coupled together for depth, let alone the use of those numbty 3/8'' twigs...lol!!

 

[sjm]

Here we go again, lol.
Page 41 of the Green OSG table 4.4(ii)
2.5mm min size when protected against corrosion and mechanical damage, ie sheathed and in conduit, buried or not buried.

 

[GLENNSPARK]

but my argument was why the hell does the pic in the OSG show 16mm CSA.....as if that CSA will make much difference to a TT earthing arrangement...lol....

 

[GLENNSPARK]

its like saying..."if in doubt just pull 16mm in"....and its that thats contemptable in my eyes.....its suggesting folk dont know.....

 

[GLENNSPARK]

patronising gets....