Where to buy electrical cable 6491X

[deema]

I’m looking for somewhere between 200 and 500m of 4mm2 in the usual 5 colours to wire up the workshop. Where’s the best place to buy it from these days and what sort of price should I be expecting? (I’m going to wire the earth in 4mm2 too)

 

[HOJ]

I can see google getting a hit searching for what 6491X is...

No help otherwise.

However, why 5 colours, can you not just use 3?

 

[Spectric]

What is it supplying, also how did you arrive at requiring 4mm ? Then is this armoured or ?

However, why 5 colours, can you not just use 3

Not if using it for three phase and neutral with a CPC . 4mm at 500 metres is a 1Km loop ! Must be looking at around a 10mV drop per amp per metre .

 

[Spectric]

Ok, you slipped in the 6491 in the title ! so these are singles for wiring within the workshop. I would use 6491 B, the low halogen version for something more industrial that you are doing and readily available. Try TLC direct or Ewardes and should not be more than about £55 per 100 metres.

 

[Sideways]

Eddies & Denmans in your part of the world ...

 

[deema]

When wiring up, I anticipate that any socket could be single or 3 phase 32A, and build in redundancy. I’ve placed trunking around the workshop at ceiling level, so to get to a machine the wiring has to run around the shop. I have 12 machines that need wiring up, and don’t have their position determined yet. I’m hopeless at layout without actually moving the machines about. Luckily @Sideways has been press ganged to give me a hand / lead the layout. He’s brilliant at creating a layout / maximising space utilisation.

500m might be two much, however it might be more economic than buying a number of rolls of 100m. My last workshop had in the end 1km of cable, mostly due to machines moving and taking the decision in most cases to put new drops in rather than jointing cables.

 

[Spectric]

When wiring up, I anticipate that any socket could be single or 3 phase 32A

Please explain. Three phase sockets, isolators etc run from the main board as individual radials from there own protective three phase device the same as 16 amp socket, isolators etc that run from there own single phase protective device and single phase sockets that accept fused plugs can run as a radial looped in and out so a string on a given protective device that would be 32 amps if run in 4mm. Here you need to do some thinking as you can run these in 2.5mm cable and use a 20 amp protective device bearing in mind that you will probably have several radials to different areas.

and taking the decision in most cases to put new drops in rather than jointing cables

Done correctly there are no issues, but good practice does state no joints within the trunking so you would need to use an enclosure so the cables exit and re enter the trunking with decent connectors.

 

[deema]

@Spectric I really appreciate your insights and questions. Hopefully I can explain my logic. Any radial drop for a machine could be over the passage of time a say a 16/ 32A Single phase or 3 phase, or anything in-between as things change. My workshop over the last seven years changed both in where things were positioned and as I updated / changed machines. So, in anticipation that this will continue…..as I am a bit of a magpie, what ever a drop is designated to be to begin with the initial shop layout I will just run it in 4mm, that way I can change it by either adding extra phases or isolating phases phases to adapt it to what it needs to be. (I appreciate that also involves changing the isolated output socket as well as the distribution board)

The ring main for 13A sockets will probably be run in 2.5mm (probably twin and earth as it’s cheaper than singles) (I need to do the loading calcs as I’ve a feeling the length / load may need 4mm2, what do you think?) it’s around 70m (50m in the trunking) run including the drops.

 

[Spectric]

probably twin and earth as it’s cheaper than singles

But remember the CPC in a 2.5 mm T&E is only 1.5mm and if running trunking then sticking T&E in there will look like a short cut, 2.5 singles are not that expensive and again will offer more flexability in the future. Also something to note is that you should keep all your 13 amp sockets fed from the same phase within the workshop.

The ring main for 13A sockets will probably be run in 2.5mm

Ring mains are historic, search the forums as it has been discussed. Use radials for your 13 amp sockets and that means that once you reach the last socket there is no cable run back to the board. If using 4mm cable and a 32 amp circuit getting two 4mm cables into the face plate can be tight, in these cases using small enclosures and Wago connectors is the solution. Do the calcs on loading and run your 13 amp sockets from several radials, that way you will not have a 70 metre run and maybe use one for say half the workshop and another for the other half so then you might find you can use 2.5mm singles and a 20 amp protective device.

 

[deema]

@Spectric I know rings are ‘old fashioned’, but they do provide IMO redundancy for a single CPC fault. I kind of favour running a radial rated cable but making it into a ring. Sounds daft I know, but it means should the CPC connection fail anywhere I have a back up circuit.

 

[Dabop]

But remember the CPC in a 2.5 mm T&E is only 1.5mm and if running trunking then sticking T&E in there will look like a short cut

Interesting, I'd forgotten the UK undersizes its earths in a TPE- here in Australia, all three conductors in a TPE are the same size- so a 2.5mm TPE has all three are 2.5mm^2 in size... (it's been a while since I dealt with UK stuff lol)

Same goes with any other size TPE/TPS- 4mm^2 has a 4mm^2 earth, all the way up to 16mm^2 TPE- has a 16mm^2 earth too...

Another difference is ours is 'presleeved' we haven't used unsleeved/bare copper since the 1980's when it became law that all new installs were done with three insulated wires inside a cable...

Rings have never been a thing here- all circuits are individual radials for 15A outlets or above, but the standard 10A 'powerpoint' ie outlet is allowed up to a dozen on a 'radial off a radial off a radial' daisychain ie the feed from the 'fusebox' (consumer unit) from a 20A RCD (RCB in the UK) goes to the first powerpoint, then there is a feed off to the next one and so on along the line... (no junction boxes are normally used, it's just two cables joined at the powerpoint itself in its terminals...)

Each three phase outlet has to be on its own individual feed as well as each individual 15A or 20A powerpoint...

Another handy feature of Australian powerpoints- a 10A plug will fit in a 10A, 15A or 20A outlet, and a 15A will fit a 15A or 20A outlet, but a 20A plug will only fit a 20A outlet- all 'compatible' but restricted to only powerpoints that will handle the load...)

10A powerpoint

15A powerpoint (note the 'longer' earth hole at the bottom with a corresponding larger pin on the plug- 10A plug earth pin fits in the 15A outlet, but not vice versa...)

20A powerpoint (this ones a bit harder to spot in a photo), but all three pins are the same size as the 15A earth pin- spacing stays the same and a 10A plug or 15A plug will also safely plug into it...

 

[Sideways]

Love that Australian flat thermoplastic cable !
The hierarchy of outlets is clever too.

 

[Sideways]

@Spectric I know rings are ‘old fashioned’, but they do provide IMO redundancy for a single CPC fault. I kind of favour running a radial rated cable but making it into a ring. Sounds daft I know, but it means should the CPC connection fail anywhere I have a back up circuit.

I did this in my much smaller shop and consider it a good solution. I had no issues getting a couple of 4mm singles into the terminals of any metalclad faceplate.
One oversized loop around the wall pretty much sorts the 13A outlet requirement. As all your machinery will be on switched CE sockets all you are catering for is chargers, electronics and corded powertools.
Need a temporary concentration of mobile power somewhere, just make up a tough rubber extension lead fed from a 16A CE plug.

I do agree with @Spectric that rings are archaic and we should stop installing them in homes, but for this application it is actually an elegant and robust solution.

 

[Spectric]

but for this application it is actually an elegant and robust solution.

Why and what makes it elegant ? You are running a cable from the board round the workshop and back to the board when you can just run from board to the last socket with no return.

I have never used a ring in an industrial premises, used to use rings in the 90's if I had to do domestic which I would go out of my way to avoid as industrial was a nicer enviroment. The days of having a six way board with a couple of rings, upstairs / downstairs lighting circuits and a cooker point are gone, there is much more design involved today with many more circuits where you address the intended loads rather than just throw in 2.5 for power, 1.5 for lighting and 6 for the cooker.

 

[Spectric]

Interesting, I'd forgotten the UK undersizes its earths in a TPE

Yes that has caused issues with some installations using long cable runs when it comes to final testing and type C protective devices when you find the loop impedance is either marginal or to high.

but they do provide IMO redundancy for a single CPC fault.

Think about that statement and add "under a fault condition" ! You have a 32 amp protective device but would only have a 1.5 mm CPC that potentially would need to handle 160 amps and that is enough to make it act like a fuse wire. On the other hand if one of the lines went open then you have a 2.5mm cable protected by a 32 amp device . Yes I really dislike rings, testing them can be a nightmare and for some reason people like adding things and modifying them which can then be another problem for someone else.

 

[Jake]

But remember the CPC in a 2.5 mm T&E is only 1.5mm

And the same on 4mm T&E of course.

 

[Sideways]

Why and what makes it elegant ? You are running a cable from the board round the workshop and back to the board when you can just run from board to the last socket with no return.

Subject to doing the maths on voltage drop etc:
He'll be putting in sockets around the wall of one big room, so the cable is following the same route whether you put in a ring or two radials each going halfway around and near enough meeting at the opposite side of the room.
The topology actually suits a ring in this instance.
The owner / user is an EE so all the usual caveats about domestic installations being abused, hacked, etc shouldn't apply as he'll know better.
Wire the CPC in 4mm and the caveats about undersize earths don't apply. It's a modern build so RCD protected on top.
Wire the line conductors in 4mm and the wiring is sufficient for a 32A breaker even in single fault conditions.
With a ring, you have two 4mm conductors sharing the load when you get a concentration of demand in any one part of the shop as you might when just one or two people are doing tasks around a particular piece of floor at one one time. That's why I like it in this very specific situation.

 

[Dabop]

And the same on 4mm T&E of course.

Its not until you get up into the truly huge sizes that you see the 'undersized earth cable' start to appear with some brands (which are best avoided imho)- the 10mm^2 TPE has a 4mm^2 earth, and the 16mm^2 TPE has a 6mm^2 earth conductor
(which is stupid imho- as the earth fault conditions are the maximum current a device would ever see, and the earth wire is smaller than the normal load carrying conductor??? WTF???)
And yes, we got 16mm^2 'flat' TP available here lol

A 'proper 16mm^2 TPE/TPS should always have all three the same size imho

rather than the UK version...

look at that ridiculously small earth cable...
That could be required to handle the full fault condition (limited only by the circuits wiring resistance!!!)

As 'The Mask' likes to say....