Earth size for TT

[TJC1]

Got chatting to another electrician today who said about using 16mm earth for TT. Not that i have ever had to put steak in but am i right in saying its 10mm for a TT system?

 

[telectrix]

it's 2.5mm min. if protected mechanically and against corrosion. and my steak is in the pan, ready to cook with chips.

 

[Baddegg]

I thought it could be a minimum of 2.5 with mechanical protection.....depends on ze obviously

Beat me @telectrix

 

[TJC1]

sweet. 10mm fine then

 

[Deleted account]

sweet. 10mm fine then

I’d rather use ( and do use) 16mm . Need to get the Ze as low as practically possible. Not just under the 200 ohm threshold.

 

[Pete999]

it's 2.5mm min. if protected mechanically and against corrosion. and my steak is in the pan, ready to cook with chips.

Had my Steak for tea yesterday nice it was as well

 

[Dave OCD]

With a TT arrangement and assuming the rod or rods is relatively close to the MET the Ze will not be significantly different whether you're using 2.5mm,4mm,6mm,10 mm or 16mm. Although I'd always use 10mm just for the mechanical strength and durability.

 

[Des 56]

I would be happy to use 2.5 mm protected
I suspect any reduction of earth resistance by using larger size cable to ground (other than for reasons of mechanical protection) is minimal,driving in longer electrodes would probably help,but why go to all the trouble when the cable generally only needs to carry 30 m/amp to operate a RCD,your 10mm should be fine if your not burying

 

[James]

I would also be inclined to use 10mm
as above, it has more physical strength, who really wants to add mechanical protection to a cable so they can save £5 on the job?
10mm is always on the van so it just seems like a good choice for 99% of the jobs.