Discuss Example of use of Adiabatic Equation. in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net
so im trying to work out the minimum size main earth for main supply ze=0.11 its a tncs supply i would say k=143 and for the main consumerunit i would say its 5 second disconection time so
230/0.11=2091
so doing the caculation i get 32.9mm and this cant be right what am i doing wrong it must be T
a bs 1361 will go quicker than 0.1 s at that fault curent.
so taking pg 244 time/current characteristics for 1361 60 a fuse at 5 seconds is 330A so doing the calc again i get 5.16mm this is better but what is right or for a consumerunit disconection time is it 0.4
please help i done it on a pir with a 6mm main earth which i doubled up to 12mm but minimum size is 5.16mm now this is safe just not conforming to bs7671 2008
Do you apply the sq root before before dividing by the K factor?Just a quick question on the rules in maths if this thread is still live. In the equation do you apply the sq root before before deviding by the K factor ? If you do the sq root last, the answer is vastly different.
Mick
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