Just checking our new wiring to figure out the cost and quantity of the sockets etc and noticed that while the Live and Neutral are 2.5mm², the ground wire has all been done in 1.5mm². All of the sockets are grounded but (as in a previous post) the lighting fixtures aren't.

I always thought that all three wires should be 2.5mm² - your advice on this would be appreciated. It's not too late to get this sorted out (ie I still owe a significant sum) but I'll need to act fast and I won't be popular!

Reduced CSA of the ground conductor is standard in the UK, it saves money obviously. Of course the systems there are design verified and/or loop measurements made at the time of installation to ensure that the protective device will operate in the prescribed time, something unheard of here.

In reality, unless you have very long runs and assuming you have an RCD then 1.5 will be just fine.

Many thanks, Crossy.

The size of earthing conductor is determined by the size of the current carrying conductors. Normally 2.5sqmm is the minimum for an earth conductor unless it is laid up in the same sheath as the current carrying conductors.

In Thailand the earth conductor size is 1.5sqmm minimum for 2.5sqmm curent carrying conductor. This complies with Thai standards.

Here is a guide.

2.5 sqmm active, 2.5sqmm earth.

4.0 sqmm active, 2.5sqmm earth.

6.0 sqmm active, 2.5sqmm earth.

10.0 sqmm active, 4 sqmm earth.

16.0 sqmm active, 6 sqmm earth,

25 sqmm active, 6sqmm earth.

Minimum size of main earth 4.00sqmm.

Ref AS3000.

Otherwise as Crossy states, you should have no problems.