2.5mm on 32A MCB

[DPG]

In design terms cable must carry less than or equal to the protective device. i.e. 32a protecting a 17a ccc does not meet this criteria. Look up Ib In and try not to make me do it please

Look up non-fused spurs from an RFC. Haven't got the regs in front of me but would be interested to see what they say. Appendix 15. Daz

 

[westward10]

Which reg is it contravening?

How is the 4mm installed.

 

[FatAlan]

I thought Iz had to be greater than or equal to In otherwise the cable would fail before the protective device?

 

[The Ghost]

Appendix 15 shows one double socket is ok only. That is in 2.5, but I think if I came across that I would advise the client this is potentially hazardous, and in design terms fails on 433.1.1 although I could just about believe one double socket may not overload 6 sockets have a high potential to do so. Anyway if I was installing the circuit I would no way do it that way.

 

[The Ghost]

Yeh you are right thats what 433 etc. says I just worded it wrong my brain is a bit fried having just completed a couple of hundred pages of EICRs. @FatAlan

 

[DPG]

Appendix 15 shows one double socket is ok only. That is in 2.5, but I think if I came across that I would advise the client this is potentially hazardous, and in design terms fails on 433.1.1 although I could just about believe one double socket may not overload 6 sockets have a high potential to do so. Anyway if I was installing the circuit I would no way do it that way.

But the OP says it IS one double socket fed from the 2.5mm Daz

 

[7029 dave]

What do you mean what cable is the 4.0? It's bog standard 4mm+1.5mm cpc T&E. Length 1m. If someone adds another socket from the 2.5 in future, that's their look-out.

Yep, you could say the same, somebody could spur a spur off on RFC .

 

[The Ghost]

Yep just reread it and your right I think i'll hush up my mouth

 

[Wilko]

So - are we saying that a 5m spur in 2.5 protected by 32A mcb is ok?

 

[HandySparks]

So - are we saying that a 5m spur in 2.5 protected by 32A mcb is ok?

Yes, if there's only one accessory on the end of it.

Not something I'd install, but I wouldn't be rushing to change it either if found.

 

[hightower]

In bah humbug mode - I think the max length by reg xyz is 3m

I'm not sure there is a regulation stipulating max length. I think the 3m length reg you are thinking of is specifically for pendants with smaller flex.

So a scenario: you need to install an extractor fcu and the ONLY circuit you have accessible to take it off is the cooker on a 32A breaker. Does that mean you take it from the cooker point in 4mm+ to the fcu, or would you take it in 2.5?

 

[kingeri]

Thanks everyone for the input. I am happy it was not just me who this got thinking.

 

[Wilko]

I'm not sure there is a regulation stipulating max length. I think the 3m length reg you are thinking of is specifically for pendants with smaller flex.

So a scenario: you need to install an extractor fcu and the ONLY circuit you have accessible to take it off is the cooker on a 32A breaker. Does that mean you take it from the cooker point in 4mm+ to the fcu, or would you take it in 2.5?

I think 433.2.2 gives us up to 3m grace (if I'm reading it right) to use the smaller cable to get to the fcu. I was thinking there had to be some give and take in the scenario you mention, but what limits it? 433.2.2 was all I found. Always happy to learn though

 

[westward10]

Still don't know how the 4mm is installed.

 

[westward10]

I'm not sure there is a regulation stipulating max length. I think the 3m length reg you are thinking of is specifically for pendants with smaller flex.

So a scenario: you need to install an extractor fcu and the ONLY circuit you have accessible to take it off is the cooker on a 32A breaker. Does that mean you take it from the cooker point in 4mm+ to the fcu, or would you take it in 2.5?

To shove 2.5 conductors in with 6.0 is just plain poor practice.

 

[hightower]

To shove 2.5 conductors in with 6.0 is just plain poor practice.

How so?

 

[kingeri]

Still don't know how the 4mm is installed.

Ref method C.

 

[Midwest]

Poor practice, but there you go.

I seem to remember someone starting a thread, annoyed at people stating something was 'Good practise', but here's a personnel statement that something is 'Poor practise'. You can't have it both ways

 

[kingeri]

I seem to remember someone starting a thread, annoyed at people stating something was 'Good practise', but here's a personnel statement that something is 'Poor practise'. You can't have it both ways

I agree. Also, it would be nice to have something more like, "I think that is poor practice because....".

I often see things which I think may not be the best way of doing something, but I can't automatically C2 it because I don't like it!

 

[davesparks]

How so?

the size difference between 2.5 and 6 means that the 2.5 is unlikely to be properly clamped by the terminal screw. With great care it is possible to do, but better to stick with similar sized conductors in one terminal.