Adiabatic equation Question

[jimmer]

I have just done a periodic on a flat that is supplied by 16.0mm pvc T&E (6.0 mm cpc only earth conductor) on a 60A 1361 switch fuse on a TN-S system. The DB Ze at the flat is 0.21 No matter what way i'm doing my sums i cant seem to get what i think is the right answer. I get 3.01mm minimum cpc is this right?
Any help much appreciated

 

[Des 56]

3.01 is my calculation as well

 

[Danny Pross]

Hi
With the info you gave I get 3.01 also.

But I thought that ZS should be used rather than ZE?
If you use the Max tabulated ZS for a 5sec disconnection (0.7 from table 41.4 p49), you get 230/.7=328.6 as I
I squared is then about 107958.
t from Fig 3.1 (p244) is then about 5sec on 328A
106958*5=539790 root=734.7
k=115
734.7/115=6.38

So assuming that your actual ZS is less than the 0.7 max, your 6mm CPC would be ok.

The 3.01 you had originally also just confirms that a 6mm would be ok - not that you should use 3mm.

But I really think it should be based on ZS

I hope this is helpful - and am more than happy to be corrected if I have gone wildly wrong on this.

CH

 

[jimmer]

Hi
With the info you gave I get 3.01 also.

But I thought that ZS should be used rather than ZE?
If you use the Max tabulated ZS for a 5sec disconnection (0.7 from table 41.4 p49), you get 230/.7=328.6 as I
I squared is then about 107958.
t from Fig 3.1 (p244) is then about 5sec on 328A
106958*5=539790 root=734.7
k=115
734.7/115=6.38

So assuming that your actual ZS is less than the 0.7 max, your 6mm CPC would be ok.

The 3.01 you had originally also just confirms that a 6mm would be ok - not that you should use 3mm.

But I really think it should be based on ZS

I hope this is helpful - and am more than happy to be corrected if I have gone wildly wrong on this.

CH

The figure quoted was DB Ze (or Zs) at the board in the flat not at the main incomer, that was 0.07. It looks like the 6mm2 is ok as the cpc. Thanks to Des and Danny