MAX Ze value for TT?

[ackbarthestar]

Which tech manual?

In the Inspection, testing and certification guide I have seen that they point to "BS7430: Code of practice for earthing which suggests that a value of earth electrode resistance exceeding 100 ohms MAY be unstable."

The NICEIC themselves have never required a max value of 100 ohms for an earth rod, simples.

Historically, I don't think this is correct , however, you're right about the NICEIC stating that 200 ohms as the acceptable value as opposed to 100 ohms in both the training books i have.

apologies for the misunderstanding

 

[Victor]

You guys are lucky you can go up to 200ohms. Here in France every installation is a TT system with a maximum value of 100ohms, which in some areas is almost impossible to reach.

However on another point, EDF here install as standard a 500mA circuit breaker on all domestic properties.