10mm 4 core SWA

[newtothis]

A mate is clearing out his garage and asked me if I wanted 30 + metres of 10mm 4 core SWA on a wooden spool.

LOL I don't know if I'm looking a gift horse in the mouth, or being a donkey carting 5 quids worth of scrap.
Could I use it to power my shed ?

1. By just terminating one of the cores and taking 25% off the CCC ?
2. Join 2 cores together as Line and neutral and use the armour as the CPC ?
3. Just not take it ?

 

[davesparks]

You have a couple of options, assuming the cable is in good condition.
Use the brown and blue for the submain, the armour for the cpc and the black and grey for L and SwL for an external light on the shed so that you can switch the light on and not walk down there in the dark.
Or just use 3 cores and connect the unused core to earth.
Either way no need to derate the cable at all, your calculations will only be concerned with the live conductors.

When checking the cable look for any damage to the sheath, and strip a bit of the sheath off and check that the armour is not corroded at all (corrosion may appear as orange rust or as a white powdery substance)
If the armour is corroded then it suggests that water has got into it, water can travel up the cable by capillary action and ruin the whole lot, this is why the ends should always be taped over when stored/awaiting termination.

And of course you can use the wood drum as garden furniture [emoji41]

 

[davesparks]

If you want to check the length of the cable you can measure the resistance of a core from end to end then look up the resistance per metre from a data sheet to work out the length. This does require a reasonably accurate measurement. Or measure the length of one turn then count the number of turns for an approximation, remembering the turns get shorter towards the centre of the drum

 

[newtothis]

Cool Mate ! Thanks for your answer, very helpful. I cheekily sawed a bit off to practice working with it.
it has got a white powdery substance, I thought that was normal as I've seen in it loads of new cable.
see pic below

 

[davesparks]

That white powder on the cores is talc which is added to stop the insulation sticking to the bedding etc. You occasionally get a bit of cable where the talc didn't get added and th sheath or bedding no sticks to the cores so that you cannot strip it.
In the pic you can see that the armour is bright and shiny, which is good. If you find the armour is dull with a white powdery deposit on the surface of the armour it is the result of zinc Galvanising corroding.

 

[davesparks]

Cool Mate ! Thanks for your answer, very helpful.

No worries, my answer was very different before I noticed this was in the trainee section!

 

[newtothis]

Thanks again, gonna shoot round and grab it tommorrow b4 he changes his mind.

 

[Marvo]

As Dave says there' s several options on how it could be used for powering your shed, it's a more than adequate size cable and the from the photo it looks like it's very good condition. I'd take him up on his generous offer in a heart beat, buy him a 6-pack of his favorite beers and say thanks.

 

[newtothis]

The cable's mine now. I would offer him a nice drink, but he's gave me the cable in lieu of a favour i did him. :teeth_smile:
Been doing some cable calcs, hmmm I could have a tumble dryer and a chest freezer down the shed, then the missus would owe me a favour :tt1:

 

[newtothis]

thoerically if I use brown and blue for the submain. I can use the grey or black for the earth, what would I do with the armour at the shed DB ? just terminate it to the metal DB and use the grey or black sleeved yellow green as the main earth to the shed DB ?

 

[davesparks]

thoerically if I use brown and blue for the submain. I can use the grey or black for the earth, what would I do with the armour at the shed DB ? just terminate it to the metal DB and use the grey or black sleeved yellow green as the main earth to the shed DB ?

It is a hotly debated topic on here!

As you have a copper core which is big enough to be a main bond whatever the earthing system (assuming normal domestic supply) then you can bond any extraneous parts in the outbuilding. This allows you to use the suppliers earth connection for the outbuilding and don't need to isolate the suppliers earth to create a new earthing system at the outbuilding.
So you can terminate the SWA in a normal SWA gland into a metal box or metal CU, having it connected at both ends will only help lower your Zs which is no bad thing.
It is permitted to connect the armour to earth only at the supply end if a core is used as the cpc, but in my opinion better to connect both ends whenever possible/practical.
The convention, but this is not regulation, is to use the black core as the cpc when using SWA on single phase (and grey as N for a 3core)

It is advisable to connect spare/unused cores to earth, at least at one end, to avoid phantom voltages appearing on them.


I am in the middle of wiring a shed for a friend which I'll hopefully get finished this weekend. I'll try and get lots of pictures to post up here of how I've done it.

 

[newtothis]

Signed off work for 2 weeks cos of a dental op that went wrong - long story.

I have a 10mm2 T&E from my house cu to a box on the wall. I had this done a few years ago when we had our extension, I was going use this to power the brick built shed at the time. The flat roof was leaking so I didn’t have it done.


Id use the 10mmSWA as suggested, black CPC grey sleeved and into the earth terminal at the metal CU

Going to have 4 socket Radial final and 3 lights one outside he shed.

Please can anyone look at my diagram and say if there’s any obvious probs with it.
[FONT=&amp]I have enough swa to go from the shed CU to the house CU but the wife won’t tolerate the inconvenience


[/FONT]

 

[Leesparkykent]

As the distribution circuit is on an RCBO you can ditch the RCD in the shed CU and just have a main switch instead. Other wise you end up with two RCDs in series.

 

[newtothis]

As the distribution circuit is on an RCBO you can ditch the RCD in the shed CU and just have a main switch instead. Other wise you end up with two RCDs in series.

Thanks Leesparky,
I was thinking of using an MCB in a spare way not protected by an RCD in my House CU.
Would that be compliant / advisable ?

Added: Seems the MCB would be more convenient not having to go the the house if it trips, Im thnking of testing too, when I do my tests with RCDs in series it will cause me probs.

 

[davesparks]

If the T&E does not require RCD protection due to being buried in the wall then yes it would be better at the shed end.
If the T&E needs RCD protection then it'll have to go at the supply end.
The reason I say it would be better at the shed end is that if it trips whilst someone is using the power in the shed then it can be reset from their without having to go in to the house