2.5mm t+e with 1mm cpc

[Blue Fox]

Hello all,

Would a ring main wired with 2.5mm t+e with a 1mm earth go down on a cert as a departure from BS7671 or in the note on existing installation box or not at all? Just done a c/u change and found ring wired with this.

Thanks

 

[green-hornet]

No it is unusual to have a cpc of 1.0mm with a 2.5 live but it is not a departure and is not required to be noted unless the disconnection times can not be achieved.

For a ring always put L-L end to end E-E end to end N-N end to end as well as r1+r2.

As long as you do not go over the maximum zs for the trip times you should be ok.

 

[Blue Fox]

Thanks for the reply, the trip times are all ok no problems there, just not sure if it needed noting on the cert.

 

[batty]

No it is unusual to have a cpc of 1.0mm with a 2.5 live but it is not a departure and is not required to be noted unless the disconnection times can not be achieved.For a ring always put L-L end to end E-E end to end N-N end to end as well as r1+r2.

As long as you do not go over the maximum zs for the trip times you should be ok.

Green giant all the first 2.5 tw/e had 1mm cpc. Most of the cables in my house are council rewired it about 30 years ago not sure when they changed it to 1.5 cpc.

Batty

 

[Blue Fox]

Green giant all the first 2.5 tw/e had 1mm cpc. Most of the cables in my house are council rewired it about 30 years ago not sure when they changed it to 1.5 cpc.Batty

The owner of this hause said it was rewired by the council she thinks in the 70's or late 60's

 

[extension15]

No it is unusual to have a cpc of 1.0mm with a 2.5 live .

It is surprisingly common..

; \

 

[extension15]

It is surprisingly common.. ; \

But my view, is these properties must be about due for a rewire (perhaps)..

 

[green-hornet]

I have not come across them often I must admit. Most of the rewires I have had to do, involve the replacement of the old imperial sizes.

I do know that prysmian cables had data sheets from the 1970,s with a 1.5 cpc with 2.5 cable they manufactured.I will keep an eye out for the 1.0mm now

 

[batty]

But my view, is these properties must be about due for a rewire (perhaps)..

Not mine I think. My neighbours has still got the original rubber. I replaced a bit in the bathroom a while back and suprisingly it was still in good condition.

Batty

 

[patspark]

hi table D.2M

14th edition 2.5/1,0

supplement on use in metric terms 1969

reprinted in metric units 1970

that should give you some idea

now i have just got to find out when the 2.5/1.5

change was made

 

[extension15]

Not mine I think. My neighbours has still got the original rubber. I replaced a bit in the bathroom a while back and suprisingly it was still in good condition.Batty

Well I did say, perhaps..

 

[binky]

1mm cpc is only an issue when protected by re-wirable fuses, which under certain circumstances do noy re-act fast enough to prevent failure of the cpc due to thermal effects. When protected by MCBs this is considered perfectly adequate for the CPC.