Comparing two 25mm² meter tails, one with 7 copper strands and another with 19 strands.
► Support this channel:
Patreon: www.patreon.com/jwflame
PayPal Donations: xo4.uk/?PPP
► Social Media:
Twitter: twitter.com/jwflame
Facebook: facebook.com/jwflame
Instagram: instagram.com/jwflame/
► Contact info, sending stuff in: etc.:
xo4.uk/?YTT
► Website - More on this video and many other subjects
Website: flameport.com
Personally i use 1 strand. Saves the early start at the gym
old me say 7, new me 19... only way to tell now is to set them on fire!!!
A funny thing, these days down here in New Zealand and Australia, inside our commercial switchboards and distribution boards, we are required to install single cores that are like the cables for a welder. IE, you might have 50mm² in from the meters to the main switch, via CT's, the wire you use there, needs to have (I could be wrong here) 625 individual cores in it, with them being so fine, you have to use either bootlace ferrules or some sort of an eyelet crimp connector on the end of it. I like this idea, back when I started my time, we used to have to solder wires into lugs, it was a pain in the rear. Personally, I also like the idea that flexible cables are being used, as opposed to mere stranded copper, the new stuff is so much easier to fit and terminate.
Try bending the 'triangulated' 25mm cores in SWA cable!
I use the Blue And Brown Tails they are the same as the supply authority use and are even more flexible.
Thanks for sharing 👍
I prefer the 19 strand tails as an electrician, the ones i get have the brown/blue outer sheath instead of the grey.
I use 19 strand Doncaster cables. Can’t seem to source the blue and brown outer sheath ones though? Mine are always grey outer. If you have a link to where you buy the blue and brown 19 stranded ones please let me know....😬
IWL Electrical Limited Ian Lawrie I bought some fromCEF recently, blue and brown, wouldn’t go back to the 7 strand again, 19 is the way to go
@@evguysltdianlawrie2274 'SHOP4ELECTRICAL' do them as well.
The 19 strand has another advantage: when connecting to a round terminal, one can use one long strand to wrap around the conductor tightly: this stops the strands from splaying out, thus making a better connection. Many years ago, this was standard practice, and some electricians also used this method when connecting final circuit conductors to fuses or breakers in dis. boards. This doesn’t work with that most nasty of cables, 2.5 sq mm T&E., or other solid conductors such as those in micc.
Sounds like a BAD idea ! Surely it's better for the strands to be able to slide over each other and be formed by the terminal hole they're being screwed down into ?
as a meter engineer i use both, but the 19 strand one is preferred in tighter scenarios, as can be bent easier...overall just get the 19 strand if you can👍🏽
Hi, what is a meter engineer? Thanks
@Keith Grout In other words, an installer. Not engineer, not even technician. Not putting down the role, but different skill sets and tasks have different terms for a reason.
@@Monkeh616 Yeah like cleaners are called sanitary engineers.
The 19-strand looks like cleaner copper :)
The 7 strand is probably a very old offcut. He didn't strip it for this video, you can see that by the shape of the strands.
More on Pro's and Con's please John?
Very helpful. Thanks
You can demo on vid which is easier to straighten - bend both into hooks, link hooks then pull apart. Hopefully the 19 will always straighten over the 7 !
I feel like the 19 strand would make better contact due to higher surface area
It's not surface area of the strands but the number of strands = the number of surfaces - so you have more surfaces to make contact with the terminal.
@@millomweb that's exactly what they said.
@@Tangobaldy It so isn't but clearly you don't understand.
@@millomweb - IT SO IS, you fucking idiot. You are simply repeating what pufferfish already said.
Just taking a moment to appreciate JW's T-shirt(s) & general clobber. Always cool.
Talking of bending cables, I hear the houses of parlement are having micc sub mains installed throughout. That must be painfull work
Definately agree here. 19 strand much easier to work with.
Tri rated is another good cable to use but probably dearer.
The 7 core tails are a nightmare to dress in to the main board especially if cold it's cold it's like trying to bend rebar with your bare hands 19 core for me..
Hi John, Thanks for your video. I prefer 19 strands as I am about to replace consumer unit in my son's house. Can you please suggest where I can buy Doncaster meter tails from? I am a qualified electrician. God bless you and best wishes, Ahmed Leicester ENGLAND
JW, I was told some years ago, by an Electrical Inspector that using Lineman pliers to twist stranded copper cables, is not only wrong, but it means the cable is wrong for the terminal size. His reasoning was that when you twist the cores, you lose copper off of the cores on the pliers and lessen the effective contact area. I still have no idea what he was on about. Most of our stuff with 16mm² and above is multi-strand (like welder cable), within feeding mains around switchboards.
It would require a huge effort to actually remove copper from the wires using pliers, by which time the wires would probably be totally destroyed. Twisting stranded wire will increase the diameter of the bundle of wires, which might make it more difficult or impossible to fit into some terminals, but that doesn't explain less contact area. Perhaps someone twisted them together, then found they were too large to fit into the terminals and cut some strands off so they would fit?
@@sparkymacsparkface7497 - generally you twist when you are inserting into a round terminal with a screw that bears down on the copper. If you don't twist, you miss half the strands. When terminating into a rectangular terminal with a rising clamp (eg: circuit breaker) then you should flatten the strands and keep them straight.
Do you need to crimp on some bootlace ferrules to the 19 strand to prevent splaying in the meter terminals? Would have thought the 7 strand might be more robust against overtighfening, closer to solid class. Thoughts?
They're still solid conductors, 1.3mm or so in diameter. No ferrule.
Is the 25mm a nominal dimension or the aggregated actual cross sectional areas of the strands. I ask because if it is the former (I.e. 25 mm2 is the area inside the brown insulation) then smaller strands should give a better packing and so the actual copper area may be higher for 19 strand than 7. Could be an appreciable difference.
It's the cross sectional area of the copper conductors. For multiple strands, it's the sum of the cross sectional area of the separate conductors. Space between them is not included, so the total area is the same regardless of the number of individual strands.
22 gauge wrapped around the bare conductor?
I'd think that more strands are also electrically less resistant, as there effectively would be more copper surface. Though that could be pedantic with AC.
Skin effect isn't relevant in this context, so no, there's no difference. At higher frequencies (50Hz being nearly DC in my world) or much higher currents, it matters, but at this level only the cross sectional area is important.
Well, if you're going to make use of all that copper surface by soldering ! I think the real benefit of more strands is the improved ability of the core to deform into the shape of the terminal hole it's clamped in- hence making more contact points with that terminal. However, if the terminal screws are properly tightened, the copper should be crushed and deformed/flattened against the terminal surface; which the 19 will do more easily.
My question is given AC likes to hug the outside of conductors as opposed to DC's strait flow, would the 19 strand give any electrical benefits. Stupid question but interesting to find out.
At such a low frequency (50Hz) the skin effect is not really relevant.
On a 50hz system skin effect in minimal so the 7 strand is fine, but whats the 19 strand for ? Motor Inverter
Unless the strands are individually insulated or separated from each other, skin effect is identical - a group of uninsulated strands together acts in the same way as a single solid conductor. Where skin effect is significant, the conductor either needs to be a set of smaller separate conductors (such as overhead power lines with 4 spaced conductors), or a different shape such as a flat bar.
@@jwflame so in a motor the individual strands being insulated makes many small paths rather than one large and skin effect changes the current carring capability at high frequency, but these wire are not enameled and act as bus but I got you JP 🤙 SO ones easier to bend than the other both act same no matter frequency allways a lesson round here fp.
@@jwflame So the answer is cost? are 7 big strands easier to... cast? Draw? BRB off to learn how copper cables are made
How Old Was You When You Received Your 1st 240 volt Belter ? And How Did You Get Interested In Electricity ? ?
Why do you capitalize every word?
@@James_Bowie - Because they are a fucking idiot.
Just a warning, on a job with EDF in attendance, they refused to fit connect their equipment to the 19 stand meter tails that I had provided. They said other supplies will allow it but not them!
When British Gas exchanged my meter last year, the installer specifically changed the 7 strand tails for 19 as part of the job. He also changed a Henley block for 2 Lucys, which seemed a bit OTT.
What about electrical or should I say electromagnetic properties with these two?
At 50Hz on conductors this small at such short lengths the effects will be minimal, perhaps even immeasurable. That said, at least _in theory,_ because AC current density is highest close to the surface of a conductor and that effect is more pronounce the larger a conductor is, the 19 strand might be expected to show a lower resistance than the 7 strand. Multiple conductors _in proximity_ add to the complexity and is more than I can get my head around. For the maths (and how significant or not the effect might be) see: core.ac.uk/download/pdf/41822519.pdf
Read meter and think“ finally they use iso standard“ and then this. I’ll take the shiny one!
We do use the ISO standand
I've used of 325mm² with 1591 strands. Each strand is just 0.2mm². It can be bent by hand to a 200mm radius rather easily. Imagine trying to bend 325mm² with only 7 strands.
A bit old school I used bind with a thinner copper wire stops spreading and better contact, meter installers used to do this all the time.Not sure if it was part of there training.
Surely a bad idea? If the strands are able to spread/deform such that they form the shape of the hole they're being clamped in, they're making better contact with it ?
We use 25mm 19 strand for interference purposes, DNO’s spec!
You say the 7-strand is 'unbranded'... surely that is now illegal? Construction Products Regulation, Declaration of Performance etc...
It has a brand on it, but it's just a dsitributor that buys it from the actual manufacturer in Turkey or somewhere. Claims to comply and all that and probably does.
@@jwflame Complies to the absolute minimum, at any rate. There was a big recall of Atlas Kablo stuff a while back as I recall, undersized conductors. Buy cheap..
@@jwflame That's not TLC is it? I've just got 100s of metres of the stuff for a house rewire (which is all in place). There's no brand but it's made in Turkey!
May i ask a out of focus question? Why both of them are in prime numbers? Is it just coincidence or is it some reasons behind?
It's how small circles can be arranged inside a larger circle. One strand = one circle, 6 others will fit around it and use most of the space = 7 strands. The next layer contains 12 strands = 19 total. After that it's 37 strands, 61 strands, 91 strands. en.wikipedia.org/wiki/Centered_hexagonal_number
@@jwflame never think of this point, now i learned, thanks.
7 strands definitely make the hexagonal shape when closely bound, and is the right number for efficiency. 19 is 7 plus 12, where the new 12 makes a single ring of strands around the original 7, again, the most efficient use of space, I guess.
Micc used to be sold in a random numbers of cores i wondered why 1-5 mm 19 core was a thing
What's wrong with 16m tails
Hi John : is it 19 strand carry more current then 7 strand in the same size wire
No... they both have the same current ratings.
No, both are the same total size.
Technically yes but in practical use at these sizes no. In transmission lines a lot of consideration is given to the number of strands and how they are grouped as skin effect and the overall surface area of the conductor can affect losses. For a set of meter tails, over a Metre or so it would make no perceivable difference.
@Indosarnia you need to understand that it doesn't fucking matter. The answer remains the same... "NO".
I've seen tails with more strands always thought DC was more used with more strands and AC less strands as Eddie currents in AC power run on the outside of the strands and DC does not encounter Eddie currents and the power runs through the centre of the strands
Well technically humans are not capable of generating power.... Back in the real world, 50Hz is far too low a frequency for the skin effect to make any significant difference. At 50Hz it makes no significant difference how the cable is formed.
@@user-jp1qt8ut3s nothing
why not use both! JUST KIDDING for more current cap!?!?!? please explain, u do realize what "the skin effect" is but this really only applies to very high freq electricity, if u were using it at 20kHz or 50 kHz you would need the thinner wires as the skin effect would REDUCE the current carrying cap with the thicker gauge
Unfortunately in a normal stranded conductor skin effect affects the whole conductor, not the individual wires so more strands of normal wire doesn't really help. There is a special cable type known of as "litz wire" that reduces skin effect by insulating the strands and then weaving them in a specific pattern, so current is forced into the center.
should the 19 strand be ferrule crimped
Not unless you have a hydraulic crimper.. This isn't exactly a fine stranded wire - those are approximately 1.3mm² each.
Nothing in the regs about crimping.
@@martinwinfield2935 Thank God for that !!! It's so illogical to me ! Main reason being that the clamp is removed - allowing the crimp to 'ease'. Whereas a terminal screw remains tightly clamped - if tightened properly.
@@millomweb What do you mean the clamp is removed? You apply the same clamping force to a ferrule or other crimp as any other conductor in the terminal.
@@millomweb - a properly crimped terminal is infinitely better, more reliable and longer lasting than a screw termination (clamp or no clamp). So you are talking out of your arse, and/or doing it wrong.
19 strand all day long please...much easier on aging hand's /elbows... big tails and big swa kills my elbows nowadays.
I swear I keep forgetting the 19 strand exists. And when I do remember, the wholesaler never has any.
I work for a DNO. We are not allowed to use 7 strand.
Why not it has been used all the time.
The 19 strand should have slightly higher current carrying capacity due to more surface area?
The external area of the sheath is pretty much identical, and it's the limiting factor in dissipation. No change in rated capacity.
C19 any less & my hand will be in lock down lol
If electrons travel along the outside of a single conductor, what would be the effect when using multi strand conductors and would more strands be better or worse?
For uninsulated strands bunched together, it's the same as one solid core - the current flow is more towards the outside of the strands as a whole. Only make a difference if the strands are individually insulated. For small sizes like this at 50Hz, the effect is insignificant anyway.
@@jwflame thanks.
Hello J.W. I enjoy your videos. Im about to do a bit of electrical work in a few days time. Im going to change the internal cables in my 5 light floor standing lamp.... The line and neutral wires in the tops of the lamp holders have gone hard and starting to brittle. no im not qualified but my work is always neat and tidy... Ive done loads of work with electrics Re wired the spot lights a friends Hair Salon. All was checked over by an engineer and passed flying colours...............
Nobody cares about your life story. Keep on topic, for gawd's sake.
What? A three-minute video from J.W.???
Perhaps he's been STRANDed by lockdown ?
What's your point?
Hi John would supplying power to an Immerser in a cylinder through an RCBO be problematic ? Earth leakage can be common in these I believe
No, if it's leaking enough current to trip an RCBO or RCD, it's faulty and needs to be replaced.
It's a lot easier to work with when fitting into consumer units.
If you have the choice and don't use 19 strand you are silly.
My only concern is terminations, the fuse board is fine as it is clamped in terminals that clamp the cable, however, the electricity meter is "screw in" to the conductor and more likely damage the thin strands. I've never had trouble with 7strands so I'm gonna stick with 7
Damage is good ! Firstly, it abrades through manky surfaces and secondly flattens the copper (to some extent) against the terminal metal making for a very good contact; hence reducing resistance at that point. Crimping does neither as it's not clamped as tightly as the crimp itself takes most of the mechanical clamping load to deform it rather than the conductor copper.
Try using bootlace ferrules, they work great in either screw clamp or screw terminals.
pmailkeey - a properly fitted crimp terminal does clamp the conductor wires. You do have to use a quality crimp terminal in a good quality crimping tool (for small wires, a hand crimping tool with ratchet action and which is calibrated to apply the correct crimping pressure. For larger conductors, a hydraulic crimping tool.
@@Mark1024MAK ferrules would be best for this I guess, where can I get a 25mm ferrule crimper from, I've only seen up to 16mm
@@MrSJT There's really no need for a ferrule for this stuff - the strands are still quite large. 'thin' is still about 1.3mm diameter here.
If you don't have the strength to bend the 7 strand , you probably shouldn't be messing with electricity...... !
You to will get old one day. Lol.