Extending a length of 2.5mm cable - what are the regs ?

[winston1]

I always recommend soldering.

 

[bernardgreen]

It can. But do the joint properly and it won't

Define properly, then give an idea of the cost involved in doing the joint "properly".

Then compare cost of buying new cable with the cost of a "proper" joint,

 

[winston1]

Then compare cost of buying new cable with the cost of a "proper" joint,

Indeed, but it has recommended to buy a new cable from the start.

 

[opps]

It doesn't have to be. It can be 25 amps. The cable is rated up to 27amps depending on installation methods. It won't instantly catch fire above that value.

I admit that I have no idea at which amperage 2.5mm T&E will catch fire.

AFAIK, 27 amps is for surface clipped cables. How many houses have rings that are surface mounted? 20 amps in trunking.

I fully appreciate that you know far more about this than I do but I am confused by your earlier statement that 32 amps is fine on one leg. If that is the case why can't a radial be 32 amps?

 

[winston1]

I fully appreciate that you know far more about this than I do but I am confused by your earlier statement that 32 amps is fine on one leg. If that is the case why can't a radial be 32 amps?

That is not what I said. I said "2.5mm cables will not catch fire at 32 amps."

Note that a spur off a ring in 2.5mm2 cable is protected by a 32 amp MCB only.

 

[SUNRAY]

That is not what I said. I said "2.5mm cables will not catch fire at 32 amps."

Choc bloc in particular is often of very poor quality or badly installed. I've encountered so many problems (yes including fires) with choc bloc/2.5mm²

 

[EFLImpudence]

AFAIK, 27 amps is for surface clipped cables. How many houses have rings that are surface mounted? 20 amps in trunking.

Buried in masonry is the same rating as clipped to surface.

 

[bernardgreen]

Indeed, but it has recommended to buy a new cable from the start.

Then stop waffling about how to join ends of cables together,

That is not what I said. I said "2.5mm cables will not catch fire at 32 amps."

but a defective joint could overheat enough to create a risk of fire

Note that a spur off a ring in 2.5mm2 cable is protected by a 32 amp MCB only.

Note also that the load at the end of the spur is limited to the sum of the fuses in the plugs. Maximum would be 26 amp ( two 13 amp fuses )

 

[winston1]

Note also that the load at the end of the spur is limited to the sum of the fuses in the plugs. Maximum would be 26 amp ( two 13 amp fuses )

A double socket with 2 unfused 2 way adapters each containing plugs could be 52 amps. But you know that anyway.

 

[opps]

That is not what I said. I said "2.5mm cables will not catch fire at 32 amps."

Note that a spur off a ring in 2.5mm2 cable is protected by a 32 amp MCB only.

Fair enough, I bow to your superior knowledge. At "normal" room temperature, at what amperage would it overheat?

Apropos the spur, given that a 2.5mm radial is only permitted to 20amps, doesn't that mean that there are diversity considerations in play?

 

[opps]

Buried in masonry is the same rating as clipped to surface.

Thanks.

When you say buried in masonry, do you mean plastered in without trunking? Most of the references that I have come across say 20amps in conduit. Out of interest, why the difference?

 

[MMarve]

I ran a lot of cables at my place with the help of my old sparky mate whose sadly passed; otherwise I would ask him. When we worked on my house he was very keen on there being unbroken cables between sockets, so that's the reason I don't already know the answer to this.

You know the bit where your old sparky mate was very keen on there being unbroken cables. And then the bit where you don't know the answer to your question. Well you do, if you think about it for a moment.

 

[bernardgreen]

A double socket with 2 unfused 2 way adapters each containing plugs could be 52 amps. But you know that anyway.

Why stop at 2 double sockets on a spur

 

[EFLImpudence]

Apropos the spur, given that a 2.5mm radial is only permitted to 20amps,

That is not so. I could be 27A if there were such an MCB - so 25A.

When you say buried in masonry, do you mean plastered in without trunking?

Yes, without buried conduit; trunking is not for burying.

Most of the references that I have come across say 20amps in conduit. Out of interest, why the difference?

Yes conduit, buried or not, is less - because the heat is not dissipated as well.

I believe the figure for conduit should actually be 19A but 'they' fiddled the figures a bit so that 2.5mm² in conduit could be used for ring circuits.
Or something like that happened.

 

[RandomGrinch]

Why stop at 2 double sockets on a spur
View attachment 279571

I guess that's for nafarious purposes!
We have plenty of these about, but at least they have a plug on the end!