SWA, T&E or tails??

[HappyHippyDad]

Evening all..

I am currently doing my first full rewire. The customer is having the wall knocked down with the meter/cutout and CU on it. the plan was to move the CU under the stairs and get DNO to move the supply to the same place. They have said they cannot move the cutout to where the CU will be. The approx length from cutout to CU will now be around 8m so I need to add a fused switch. My questions are about which type of cable to use:

1. I could use 2 core 25mm SWA (seperate 16mm earth) but I am unsure of how easy this is to bend through the route? It will be going straight up from the meter box and then 90degress into the house wall entering directly under the first floor floorboards. What is the best way to get it through the wall without putting too much strain on it (with regards bending angle)?

2. BS7671 states 25mm to be used, however I am fusing down to 80A, could I not use 16mm SWA as CCC is 87A?

3. Could I use tails as at no point will the tails be buried in the wall. They will be going directly under the floor boards from outside the house (suitable protected outside) and then down from the ceiling directly behind the new CU (there will be a cavity behind new CU as I will bring out from the wall). Do they need to be protected if they are not getting buried in the wall?

4. Which is easier to move around/use T&E (16mm or 25mm), SWA (16mm or 25mm) or tails?

5. Which is the best fused switch to use? KMF, wylex metal? Can I gland SWA into a KMF or does it need an adaptable box?

Cheers chaps:biggrin:

 

[Midwest]

wrong reg states not readily combustable so unless you coat the plastic in parafin it complies

Thats what the regs state, but I haven't seen any manufacturer going with anything other than metal. Unless you know different?

 

[Risteard]

wrong reg states not readily combustable so unless you coat the plastic in parafin it complies

No it doesn't. It states "non-combustible" - the "or not readily combustible" part in the Draft for Public Comment never appeared in the Standard.

 

[Risteard]

i cant remember manufacturer but at least one are saying there plastic boards comply with amd3

All the evidence suggests that their claim is false, however.

 

[shanky887614]

how so the un standard for non readily combustible is a lower temp than the old glow wire test

 

[Risteard]

how so the un standard for non readily combustible is a lower temp than the old glow wire test

But not readily combustible is NOT what the Requirement is - "non-combustible" is.

 

[Octopus]

But not readily combustible is NOT what the Requirement is - "non-combustible" is.

What they should had specified in BS 7671 is "metal"

Pratts!

 

[shanky887614]

What they should had specified in BS 7671 is "metal"

Pratts!

metal can be set on fire though

 

[Octopus]

metal can be set on fire though

Hum. Ok they should have specified the materials that are compliant!

 

[Midwest]

metal can be set on fire though

Wire wool, lithium in water. But most manufacturers are using mild steel.

 

[Risteard]

metal can be set on fire though

Everything can given sufficient heat!

 

[Midwest]

Everything can given sufficient heat!

I'm not a scientist, but I think that when metal is heated to a sufficient temperature it changes from a solid state to a molten state. If it's heated to a higher temperature it may actually boil and turn into a gas. To catch fire, is a state of combustion. If metal can be combustible, then it's not gonna be much use as a material for 421.1.201.

 

[shanky887614]

Everything can given sufficient heat!

exactly and certain types of plastic easily pass the new regs.

the british standard on the definition of non combustable materials can easily be met

 

[Risteard]

the british standard on the definition of non combustable materials can easily be met

But you must remember that "non-combustible" and "not readily combustible" are not synonymous.

 

[ImpededLoop]

I've used a few of these to supply submains etc & I agree top value and a decent quality unit,but I've been thinking...what about amendment 3? they don't comply eh?

I would say that they do comply when installed in an external meter cabinet as long as there's a fireproof wall between the cabinet and the inside of the property.

 

[shanky887614]

But you must remember that "non-combustible" and "not readily combustible" are not synonymous.

i cant remember the correct wording and my regs book is on the shelf and when i posted that i was 80miles away from it

 

[Guest77]

T&E only goes up to 16mm with a 6mm cpc.

Eye, years ago though they did make it to 25mm2.