Tail size from meter to cu

[malcolmsanford]

Lloyd apart from the fact that now we have established it is a TT system and they may have to change that switch fuse if the disconnection times can not be met, why are you advocating ripping out things and installing 16mm main earth conductors for a TT earth system?

 

[lloyd1980]

ah ok missed the TT bit
thanks

and on the size of he earth (16mm) if he installed it, why would this matter ??

on a TT, your resistance should be under 200 ohms , if he wanted to put in an earth cable that was 125mm that would be ok (apart from look strange )
As long as the earth isnt undersized.

Cant see why replacing the CPC from the cut out to the CU would be a bad thing ?
Yes ensure this meets the disconnection time, but why wouldnt a 16mm earth from the cut out to the CU mean the disconnection time wasnt met?

 

[malcolmsanford]

Llloyd you could use spent Dilithium Crystals from the Warp Drive of the SS Enterprise if you are so inclined, as long as by Adiabatic equation proves it will carry the fault current.

But what you can't do is advise someone that a T + E sub main on a TT installations need ripping out quick and a 16mm installed, as if that T+E is going to suddenly explode into a roaring inferno, there is no need for a 16mm main earthing conductor on a TT system, and so why advise someone that is the minimum requirements as it isn't

 

[lloyd1980]

My point was not that the 10mm would suddenly explode haha , my point was that the cpc of the 10mm twin and earth would be too small and would need to have its size increased,
for a disconnection time to be met you would need an acceptably low impedence path back to earth, this would increase the fault curent and trip the disconnect in a faster time.
The larger an earthing conductor the easier it is for the fault curent to pass through (low resistance) and then the fault current spike increases in direct relation to the impedance.
So the higher the impedance the lower the fault current and the slower the disconnect will go, breaker tripping or fuse blowing,
So the lower the impedance the higher the fault current and the faster the disconnect will go, breaker tripping or fuse blowing.
I know my stuff when it comes to this so you cant tell me that leaving the CPC of a peice of 10mm twin and earth as the main earth conductor (TT system or whatever flipping system ) will be more beneficial to a disconnection time than replacing it with a 16mm seperate earth.

Maybe they taught you to use spent dilythiam crystals from the warp drive in college

They just taught me to use copper cable, dont think any wholesaler I know stocks spent dilythiam crystals or warp drives?
Maybe its a new square D range ?

 

[malcolmsanford]

My point was not that the 10mm would suddenly explode haha , my point was that the cpc of the 10mm twin and earth would be too small So you know that, you have done the equation and it's too small .....fair enough and would need to have its size increased,
for a disconnection time...........We are talking earthing conductors here not R1 + R2, remember the disconnection times are met by both conductors not purely the size of your earth to be met you would need an acceptably low impedence path back to earth, this would increase the fault curent and trip the disconnect in a faster time.......you seemed to have grasped that
The larger an earthing conductor the easier it is for the fault curent to pass through (low resistance) and then the fault current spike increases in direct relation to the impedance.
So the higher the impedance the lower the fault current and the slower the disconnect will go, breaker tripping or fuse blowing,
So the lower the impedance the higher the fault current and the faster the disconnect will go, breaker tripping or fuse blowing.
I know my stuff when it comes to this ......Do you so you cant tell me that leaving the CPC of a peice of 10mm twin and earth as the main earth conductor (TT system or whatever flipping system ) will be more beneficial to a disconnection time than replacing it with a 16mm seperate earth..............Yes I can if I prove it by calculation

Maybe they taught you to use spent dilythiam crystals from the warp drive in college....................not sure what they taught you

They just taught me to use copper cable, dont think any wholesaler I know stocks spent dilythiam crystals or warp drives?
Maybe its a new square D range ?[/QUOTE

Well I'll have to bow to your obvious expertise on this

 

[Spudnik]

And as the OP has been instructed by his boss, we can end it there.