I wrote this very early on.
Why you say 20 amps was thinking 32 amp for main fuse ?
I gathered it was 20 amp for a 2.5 radial and 32 amp for a 2.5 ring circuit.
Cable distance is 18 meters tops.
Supply is 240v.
Thanks for reply
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//www.diynot.com/forums/electrics/electric-to-log-cabin.344050/#ixzz2CTSLYczJ[/QUOTE]
You can't even be rsed to remove that last line that the site inserts when you copy and paste a post, can you. - Just like you could not be bothered spell checking or was you getting upset and writing very fast. You seem to be good at that, getting upset that is !
Anyway...
In my loft I have a 10mm T & E cable isolated which runs to the fuse board on a 40amp fuse. I was thinking of connecting 2.5mm SWA cable to the T & E
If the fuse on that 10mm is 40amp then you can not connect 2.5mm cable to it.
The fuse would have to be reduced to 20 amp at the most.
Why you say 20 amps was thinking 32 amp for main fuse ?
First of all, he explained why he said 20A, it's because you'd said that you were going to connect a 2.5mm² cable to the 10mm² cable which is on a 40A breaker.
Secondly, you had
not said that you were thinking of changing that 40A breaker to a 32A one. But if you had, that would also have been wrong.
I gathered it was 20 amp for a 2.5 radial and 32 amp for a 2.5 ring circuit.
It is,
but you had not been talking about a ring, you had been talking about the radial to the shed, and as you had been talking about a 2.5mm² radial that is why you were told that it had to be on a 20A fuse.
Cable distance is 18 meters tops.
And there you went again, talking about the radial to the shed.
Nobody has told you that 32A is wrong for a 2.5mm² ring final.
Nobody.
Which is basically saying I understand 32 amp is for a ring and 20 amp is for a radial either way I understood it.
You gave no evidence of having understood it, and lots of evidence that you didn't get what people were telling you.
Even now the fact that you are still banging on about having been told that 32A for a 2.5mm² ring is wrong shows that you don't understand what you are writing or what you are reading.
Again I said I gathered it was 20 amp for a 2.5 radial and 32 amp for a 2.5 ring circuit. I had not even got onto designing the circuit at this stage
Wrong - you had got onto designing it, and your first design was to put a 2.5mm² cable on a 40A breaker.
either or I have confirmed what I knew with a spark and he has confirmed it to be correct .
I suggest you accept the fact that you really do not have a good enough understanding of all of this to be DIYing, and let that electrician do it all for you.