Electric to log cabin

[diycooper]

I have and they are for rings yes. wait I will find where I said earlier for ring and got told no .

 

[diycooper]

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.

 

[diycooper]

2.5mm SWA is not rated for 32amps.

Sorry for double post do not know how to do one with the quotes. I was not saying 2.5 was rated 32 amps I was saying it was protected with the next fuse up 32 amps ?

This is what 2 of my properties are and I have read is ok for ring but gold told no.

 

[SimonH2]

Sorry for double post do not know how to do one with the quotes.

If you mean, quote two different posts in one reply, then you have to hit reply to one post, copy the text, then go back and hit reply to the other post before pasting the first lot of quoted text in before or after the second lot. It's help if you use the "open in new tab" function of the browser so you can :

Click Quote to post 1 while holding the modifier for "in new tab" (or right click and select from the menu), copy all the text in the box, close the tab.
Click reply to post 2.
Paste in the copied text before or after what's already there according to context.
Trim all the quoted text - should be enough to show context.

I was not saying 2.5 was rated 32 amps I was saying it was protected with the next fuse up 32 amps ?

This is what 2 of my properties are and I have read is ok for ring but gold told no.

2.5 is 'usually' OK for a ring (Ring Final Circuit, RFC). That's on the basis that normally the load would be distributed around the ring, and so share the two parallel paths back to the distribution board - so in principal it shouldn't be possible to overload one leg if the circuit is properly designed.

However, 2.5 is not rated high enough to allow it to be used as a radial with a 30A fuse or 32A MCB. You would normally need to use a 20A fuse/MCB for a radial done in 2.5. If you want a radial supplied by a 30A fuse/32A MCB then you need the next size up of cable.

There is an exception to this, and that is when you spur off an RFC. You then have a single 2.5 fed from a 32A MCB - but the regs don't allow you to fit anything more than one outlet on the spur, thus a max of 26A if that's a double socket and you plug in two big loads (which is also probably more than most double sockets can actually handle !).

But note that cable current ratings cary with type of protection (it's lower when fed by fuses), and also with installation method - it's a lot lower if the cable is embedded in insulation, higher if fixed directly to something thermally conductive. Insulation type also affects it - but normally you'll be using PVC cables in a domestic environment.

As well as current carrying capacity, you need to consider volt drop, and loop impedance. If you use a long length of small cable, then the resistance could mean a) excessive volt drop at the end, and b) insufficient fault current to make protection trip in a timely manner. Classic example is someone using some very long extension leads to run tools in the garden. If they are long enough then it could be possible for there to be a hard L-E fault in the hand tool, but insufficient current to make the fuse blow - hence the fuse doesn't blow, the cable gets warm, but most importantly of all, while theis is going on, the tool body will be at half the mains voltage (120V) Hence the move to double insulated tools and RCDs.

 

[Taylortwocities]

Nice post Simon.

It made me have a good look through my copy of Ohm's Law and I see that most of what you say is not covered by Ohm's Law.

So there must be more to this electric stuff than it seems at first look

 

[ban-all-sheds]

2.5mm SWA is not rated for 32amps.

Sorry for double post do not know how to do one with the quotes. I was not saying 2.5 was rated 32 amps I was saying it was protected with the next fuse up 32 amps ?

Yes, but how can you "protect" a cable rated at less than 32A with a 32A device?

• //www.diynot.com/wiki/electrics:mcbtocable
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm
  
  
• http://www.tlc-direct.co.uk/Book/4.3.11.htm
  
  
• http://www.tlc-direct.co.uk/Book/5.3.1.htm
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/cableselection_web.pdf
  
  
• http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
  

This is what 2 of my properties are and I have read is ok for ring but gold told no.

No, you weren't told that.

I was thinking of connecting 2.5mm SWA cable to the T & E in the loft then running it down my house and burying underground to the shed.

That's not a ring.

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 ?

I gathered it was 20 amp for a 2.5 radial and 32 amp for a 2.5 ring circuit.

But your single run from the house to the garage is not a ring.

 

[diycooper]

2.5mm SWA is not rated for 32amps.

Sorry for double post do not know how to do one with the quotes. I was not saying 2.5 was rated 32 amps I was saying it was protected with the next fuse up 32 amps ?

Yes, but how can you "protect" a cable rated at less than 32A with a 32A device? With a ring which is what I was implying very early on in the thread.

• //www.diynot.com/wiki/electrics:mcbtocable
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm
  
  
• http://www.tlc-direct.co.uk/Book/4.3.11.htm
  
  
• http://www.tlc-direct.co.uk/Book/5.3.1.htm
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/cableselection_web.pdf
  
  
• http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
  

This is what 2 of my properties are and I have read is ok for ring but gold told no.

No, you weren't told that.

I was thinking of connecting 2.5mm SWA cable to the T & E in the loft then running it down my house and burying underground to the shed.

That's not a ring.

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 ?

I gathered it was 20 amp for a 2.5 radial and 32 amp for a 2.5 ring circuit.

But your single run from the house to the garage is not a ring.

 

[diycooper]

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

Read more: //www.diynot.com/forums/electrics/electric-to-log-cabin.344050/#ixzz2CTSLYczJ

Which is basically saying I understand 32 amp is for a ring and 20 amp is for a radial either way I understood it. And I also understand that if you want to use 32 amp fuse on a radial to use a higher cable like 4mm or 6 mm ?

I think we got are wires crossed ha no pun intended .

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 just clarifying my understanding with yous before I started to discuss the circuit, either or I have confirmed what I knew with a spark and he has confirmed it to be correct .

 

[ban-all-sheds]

I can't believe that someone who over the course of nearly 6 years has made 533 posts here, and read hundreds too, still doesn't understand how to use [quote] [/quote] properly.

The truth is you just can't be bothered, can you.

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

Read more: //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.

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.

 

[diycooper]

So when I said I gather its 20 amp for radial and 32 amp for a ring did that not make to you that I ment 32 mp for ring and 20 amp for raidal. Listen you can all pick bits out of a long thread and use them in what way you want.

I do understand that if I can use a 32 amp MCD which is connected to 10 mm T & E. Then connected to 4mm / 6mm SWA fed to my shed, Then the SWA connected to 2.5mm T & E on a radial and a 13 amp FCU for light. I was asking them questions to clarify my understanding. And yes I was talking about a radial but you can have 32 amp MCB on a raidal with the right cable and I Was asking cable size !

 

[ban-all-sheds]

wait I will find where I said earlier for ring and got told no .

We're still waiting.

 

[JohnW2]

wait I will find where I said earlier for ring and got told no .

We're still waiting.

I've been trying to make some sense of what the OP has been saying. Is it possible that one of his confusions is that he thinks (obviously incorrectly) that if 2.5mm² is OK for a 32A ring, then it should also be OK for a (single) cable 'feeding' that ring?

Kind Regards, John

 

[ban-all-sheds]

IHNI.

All I know is that I have no confidence that he understands what people tell him, nor any that the electrician told him what he thinks he did.

 

[diycooper]

wait I will find where I said earlier for ring and got told no .

We're still waiting.

I've been trying to make some sense of what the OP has been saying. Is it possible that one of his confusions is that he thinks (obviously incorrectly) that if 2.5mm² is OK for a 32A ring, then it should also be OK for a (single) cable 'feeding' that ring?

Kind Regards, John

This is not the case as I know the feed cable is not on a ring and directly from consumer unit,

 

[diycooper]

This is turning into a arguement than advice. If you do not think I understand then ask me questions now and I will answer them correctly, this way that will prove it instead of going threw topic which is all messed up and basically is going to get nowhere .