Pros...cons...preferences..

[Deleted member 26818]

Hi - so are you saying that GN8 is wrong or that I’ve read it wrong? .

Don’t know what GN8 says.
I just go by the sizes for the British Standards and the values for K in BS7671.

 

[Deleted member 26818]

Am I missing something here?
If you know that the cpc is 26mm, why do you need to do the adiabatic?
Apologies if I'm being stupid.

If the CSA of the Steel Wire is 26mm2.
It’s not a given that the copper equivalence will be sufficient.

Here’s a link to a chart produced by John Peckham, for at a glance checking the CSA of the Steel Wire is sufficient:
Use SWA as CPC, a guide to the acceptability of steel wire armour use as CPC. - https://gadsolutions.biz/regulations/swa-as-the-cpc

Sure this has been posted in the past.

 

[Pretty Mouth]

Baddegg, my experience of the adiabatic is limited too, hence the question. Just about getting my head around it now though, i think.

Charlie, the name Pretty Mouth comes from the movie Deliverance (my favourite romantic comedy), what makes you so sure I'm a boy? Haha

 

[Deleted member 26818]

Must admit, I hadn’t noticed that he Baddegg used Cmin in his calculation.

 

[Charlie_]

All this talk of Cmin and pretty mouth is getting too much for me

 

[Deleted member 26818]

Just realised he didn’t use tabulated value for the tripping current.
So yes t should have been 0.1s.

 

[Baddegg]

If the CSA of the Steel Wire is 26mm2.
It’s not a given that the copper equivalence will be sufficient.

Here’s a link to a chart produced by John Peckham, for at a glance checking the CSA of the Steel Wire is sufficient:
Use SWA as CPC, a guide to the acceptability of steel wire armour use as CPC. - https://gadsolutions.biz/regulations/swa-as-the-cpc

Sure this has been posted in the past.

That’s where I got the 41 mm2 from....

 

[Baddegg]

If the CSA of the Steel Wire is 26mm2.
It’s not a given that the copper equivalence will be sufficient.

Here’s a link to a chart produced by John Peckham, for at a glance checking the CSA of the Steel Wire is sufficient:
Use SWA as CPC, a guide to the acceptability of steel wire armour use as CPC. - https://gadsolutions.biz/regulations/swa-as-the-cpc

Sure this has been posted in the past.

That’s where I got the 41 mm2 from....

 

[Deleted member 26818]

That’s where I got the 41 mm2 from....

My chart is slightly different from John’s.
Not really sure why?
I have 40mm2 for 2 core 10mm2, and I also have the 26mm2 for the 90 degree C flagged up as requiring verification by calculation.
Might be that it may not be acceptable for some protective devices?

 

[Baddegg]

Thanks spin, I’ve got the 90c 6942x bs 5467 cable so looks like it doesn’t comply unless by calculation.

 

[Deleted member 26818]

If you use tabulated values, it works out that you need 9.72mm2.
i.e. 200a tripping current for 40A MCB, 5s tripping time for distribution circuit.

 

[Baddegg]

By my new sums using measured values I get 4.16 so either way I’m good, thanks again

That’s using 0.1s tripping from the curve charts...

 

[Tony Reidy]

after my rather vague thread Friday about finding the 30 mtrs of 10mm 2 core swa In the back of me van.....after some views on earthing to the shed, 3 options as far as I’m aware are
1. Run a single 10mm from main met upto the shed and use that
2. Use the armour of the swa, adiabatic permitting..
3. Connect the swa to the main met at source end and TT the shed
Each option is appruthe same cost wise and it’s my own house so Labour is not a big issue, as per title just after others views and preferences....

Depending on which body you talk to the armour on swa is acceptable to cable that has cores of 95 mm and under but it's never a bad idea to bring A10 g/y with it

 

[Charlie_]

Ive has experience of some wholesalers no longer stocking 2 core swa..
I put this down to another effect of the dumbing down of the trade..

 

[Tony Reidy]

You think the cable is amusing....I’m off to do the adiabatic! Wait till I post them maths up ha ha ha

Do the maths don't forget about the insulation double thickness over and under the cable,will work out you need to use 6 mm t+e to do a lighting circuit

 

[Baddegg]

Do the maths don't forget about the insulation double thickness over and under the cable,will work out you need to use 6 mm t+e to do a lighting circuit

Im dying here Tony......you’ve lost me there sorry

 

[Tony Reidy]

Im dying here Tony......you’ve lost me there sorry

Sorry mate,you the one who used the word adiabatic I thought it was about thermal effects

Im dying here Tony......you’ve lost me there sorry

 

[Wilko]

I’m just going to remind that 10mm twin and earth typically comes with 4mm of copper for its cpc.

 

[freddo]

I’m just going to remind that 10mm twin and earth typically comes with 4mm of copper for its cpc.

Need some of the cool Irish stuff. Got some 16mm t+e here, 16mm CPC.

 

[ipf]

Need some of the cool Irish stuff. Got some 16mm t+e here, 16mm CPC.
View attachment 49083

I like it...…...t'b sure.