Problematic Ze........

[Ian1981]

Will try, just PM me your address to mail the charred remains to........

What mft is it?

 

[westward10]

The tester will not be able to recognise if the leads are both at neutral as opposed to neutral and earth.

 

[Wilko]

0.35 is a typical value for a 100A fuse at the head. I suspect the reason they reduced the fuse to 80A is to allow for a higher Ze of 0.50 but I can't recall the exact figure.

Correctamundo - 0.38 for 100A and 0.51 for 80A (Table 41.4 BS88-3 with 5sec)

 

[Ian1981]

Correctamundo - 0.38 for 100A and 0.51 for 80A (Table 41.4 BS88-3 with 5sec)

For a bs 1361 type 2 80amp is 0.48
100amp is 0.34
This is at operating temperature not the 0.8 rule of thumb.

 

[Ian1981]

Correctamundo - 0.38 for 100A and 0.51 for 80A (Table 41.4 BS88-3 with 5sec)

Is that bs 88-3?
Never mind

 

[Dave OCD]

All this is academic really if all circuits within the installation are 30ma RCD protected, it would have been more relevant in the past before such widespread use of RCDs was regulatory.

 

[Ian1981]

All this is academic really if all circuits within the installation are 30ma RCD protected, it would have been more relevant in the past before such widespread use of RCDs was regulatory.

It becomes academic if the protective device in the cut out takes longer than 5 seconds to disconnect due to a high ze/zs at the origin.

 

[Dave OCD]

Yes of course but any circuit fault with RCD and MCB protection will disconnect well before the main fuse gets involved.

 

[Ian1981]

Yes of course but any circuit fault with RCD and MCB protection will disconnect well before the main fuse gets involved.

But if the ze is high when measured at the incoming main switch and above what is required to disconnect the fuse in 5 seconds at the cut out then that's ultimately the issue.

 

[Andy-1960]

Wait for us to have a really good wet spell, then visit site again!