Zs to high on MCCB Protected circuit?

[shanky887614]

Why is that?

0.8ze for a distribution circuit is quite high with other circuits coming off it, maybe not now but in the future when they go to expand.

just did a quick google search and 4c 70mm swa is £23m.

for 500m thats 12.5k surely it might have been a better design for another supply from the grid.

especially if they only needed a 30amp supply

 

[Leesparkykent]

0.8ze for a distribution circuit is quite high with other circuits coming off it, maybe not now but in the future when they go to expand.

just did a quick google search and 4c 70mm swa is £23m.

for 500m thats 11k surely it might have been a better design for another supply from the grid

Or two cables in parallel maybe. Back in the day when I was subbing we once pulled in a cable cant remember the distance but I know the cable cost 12k and it come up about 50meters shy of where it was supposed to go lol. Btw the measuring/ordering of the cable had nothing to do with me lol.

 

[Flanders]

0.8ze for a distribution circuit is quite high with other circuits coming off it, maybe not now but in the future when they go to expand.

just did a quick google search and 4c 70mm swa is £23m.

for 500m thats 12.5k surely it might have been a better design for another supply from the grid.

especially if they only needed a 30amp supply

but the OP said he was putting in an upfront rcd would that not cover the disconnection time for all final circuits aswell , saying that i don't think the design is the best but we don't know the resons for the design and there could well be a good reason fot it

 

[shanky887614]

but the OP said he was putting in an upfront rcd would that not cover the disconnection time for all final circuits aswell , saying that i don't think the design is the best but we don't know the resons for the design and there could well be a good reason fot it

true but i cant see why the original installer did this

 

[biospark80]

To complete this issue I've been in touch with Schnieder as it was there MCCB in the panel, they have provided a Vigirex unit with a Toroid and a shunt trip. This is a essentially a earth current monitoring device rated from 0.3-1 amp and the shunt trip attaches to the MCCB to activate the tripping mechanism.

 

[biospark80]

Hi the original installer, has made a huge mistake. I can only assume because he was separating the earth at the load end and creating a TT ( again not sure why as it is a TN-S system, lack of research i think.) he thought that he didnt require the Zs value at the end of the supply cable.

true but i cant see why the original installer did this