6mm earthing conductor

[juanpabs]

Seen something today while performing a fire alarm test at a relatively sized office that struck me as strange. Thought there was no better place to query it than here. Like I said decent sized office, 3 phase tn-c-s supply can't really say too much more about the installation because this wasn't what I was there for, but i think I remember seeing 5 separate DBs on my way around so quite a large load yet only a 6mm earthing conductor! Now most commercial supply's I've seen have at least a 10mm earthing conductor, noticed the periodic warning which says it was done previously, less than 5 years ago! So I would presume that it all calculates correctly or this would have been sorted then?

 

[trev]

Without doing the adiabatic there's no real way of knowing.

 

[Richard Burns]

A 6mm² earthing conductor would likely comply with the requirements for minimum csa as regards the fault current and was probably installed some time ago and has never been upgraded to meet the current requirements of minimum 10mm² for TNCS.