6mm earthing on a TT system

[james king]

hi all i ahve been reading up on tt systems am i correct in saying that a tt system can have a lower earthing conductor than a tncs or tns? can anyone explain why? and also what is the lowest earthing size u have seen on a tt system ?

 

[IQ Electrical]

You can still use the adiabatic equation on a TT system to size the main earthing conductor.
Low fault currents and fast rcd disconnection usually result in a minimal size but it's still subject to mechanical protection and corrosion constraints.

The minimum possible csa is 2.5mm with mechanical protection and 4mm without.

 

[Deleted member 26818]

4mm² is quite common.

 

[cbw]

Me too, seen lots of 4mm, both insulated and uninsulated.

I will change it to a 16mm and put a new spike in when doing a CU change.