TT system earth cable size.......

[magnoliafan89]

Hi guys

At a job doing a re wire and the electrician i was with is changing the earth cable over from 16mm to 6mm
He says as its a tt system that it only needs a 6mm.

Is this right?

 

[Ian1981]

 

[Octopus]

Odd. If 16mm is in place why change it?

 

[Deleted member 26818]

The size should be determined via the adiabatic equation.
Whilst he may be correct that 16mm is not required, there is no reason to remove it.

 

[Ian1981]

The size should be determined via the adiabatic equation.
Whilst he may be correct that 16mm is not required, there is no reason to remove it.

It’s TT earthing.
Your not going to get hundreds of amps of fault current flowing in the earthing conductor.
(Depending on Ra) but I doubt it’s any higher than the ccc of 2.5mm single which is why the table exists
Even at 10 ohms Ra that’s only 23 amps of fault current which is never going to blow the service fuse.

 

[westward10]

It is an earthing conductor not a bluddy earth cable.

 

[HappyHippyDad]

Hi guys

At a job doing a re wire and the electrician i was with is changing the earth cable over from 16mm to 6mm
He says as its a tt system that it only needs a 6mm.

Is this right?

I think there must be a reason why he's doing this as no one would remove a cable in this scenario just because a smaller cable would be acceptable..... ooops, sorry, 'conductor' . Tell us more of the story Magnoliafan?

 

[Deleted member 26818]

What’s the scrap value of the 16mm cable?

 

[HappyHippyDad]

Oi... It's a bloody earthing conductor, not a bloody earth cable.

Alright Michael, calm down

 

[magnoliafan89]

It is an earthing conductor not a bluddy earth cable.

I never once called it a "bluddy earth cable".....just....an earth cable

 

[MDJ]

I never once called it a "bluddy earth cable".....just....an earth cable

You still haven't answered the questions asked muppet?

 

[magnoliafan89]

Jeez no need for name calling just forgot about this thread. He wanted to change it as he said there was no point it being that size

 

[telectrix]

and then along comes DNO and converts to PME.

 

[Wilko]

I do new installations in 16/10 for exactly @telectrix reason

 

[westward10]

Jeez no need for name calling just forgot about this thread. He wanted to change it as he said there was no point it being that size

Must admit it is a pretty random thing to do.

 

[Andy78]

Very odd behaviour. A bit like ripping out a 6mm cooker cable and installing a 2.5mm because the current oven uses a 13A plug top.

 

[telectrix]

will a current oven cook the current buns as well on a 13A plug top?

 

[Andy78]

will a current oven cook the current buns as well on a 13A plug top?

Yes, it just takes longer.

 

[Marvo]

What’s the scrap value of the 16mm cable?

Tel will probably know off the top of his head.

 

[telectrix]

£2.50/kilo with insulation. £4/kileo bare copper..