Thread: The difference between "FLEX" and "CABLE" ??

I wanted some heavy duty flex to run from a 15Amp socket out the back yard to my portable welder, having melted some so called heavy duty 15 amp flex last time I made a run this long I went to my local Middys to byt the stuff to make my own, even tough doing so is about twice the price of a made in China from the big B.

I asked for some heavy duty flex, then I asked the guy behind the counter for 4mm*2 flex and he said that there was no such thing and if I wanted heavier than 2.5mm*2 I would need to buy cable.
Can some-one please tell me the difference between cable and flex? they look the same, they use the same copper, just more of it, why the distinction?

Bloke in Middys said I should be fine with Flex if I bought thicker insulated stuff, same copper just more PVC surrounding the conductors, and here was I thinking that the heat generated by resistance was determined by the conducting area.

Anyway 50 meters of flex was too expensive so this is on hold for a while, I guess I'll buy one from K-mart and have to chance melting a hole in it again.

Regards
ted

"Flex" has more, but smaller, strands of copper. It is designed for movement "Flexing". Cable is designed for fixed installations (no movement after installation).

Be careful of "heavy duty" flex - sometime its the insulation that's heavy duty rather than the conductors! Look for 1.5mm2 flex - you can get it at Bunnings as "Tradesman" extension cords.

You can also get flex in 2.5mm2 and 4mm2 but you'll have trouble fitting it to domestic 3-pin plug.

Do you still have the melted cable? If so, can you check if the earth cable is the one that melted. If so, let me know and I'll tell you what really went wrong.

Yes I do have it still, I shortened it but I have the end where it fused, brown conductor, the live one a section about a centimeter is gone.
I remember the circumstances too, very hot day but not a total fire dav, welding down the back about 35M from the power point.
GPO was a dedicated 15A, flex was rated 15A and had 15A plug and socket, blew at about the 38M mark ( the off cut is what I found ) I still haven't got around to putting a plug on the short bit of flex.

This was a 50 meter tradesmans 15A rated extension, we had been welding for about 3 hours when it went belly up.
Does this information help??

It sounds like a faulty piece of cable. Occasionally, if you are unlucky, you can get flex that has a join in it from where the manufacturer has spliced another run of copper in to the manufacturing process. I've assumed that they'd normally know where the joins are and discard that cable, however I have seen joins in flex.

The reason I was asking about the earth conductor was to see if a situation outlined in this thread had happened - see post #12 Electical Advice On My Welding Unit

OK thanx chrisp, then I am probably safe using 2.5mm*2 flex on a run that long?? Saves me the expense of buying new stuff
OK can I ask a related question?
B******** are selling both flex and cable and the cable is almost half the price of flex, for something that was normally going to be run a long distance and loosely coiled for storage ( I mean it comes on a roll for sale and distribution purpose ) can I substitute cable for flex and save money??

When a cable is described as being 32 * 0.25mm is that 0.25mm the diameter of the wire or its area?? I tried looking for the indformation on the Olex site but no luck??

OK I just found that info on another site, it is of course the diameter of the individual wire in the cable so 32*0.25 is 1.25mm*2 or 10 amp max?? flex

Another question, if cable is cheaper than TPE flat can it be used as a substitute legally??

Originally Posted by Moondog55

OK I just found that info on another site, it is of course the diameter of the individual wire in the cable so 32*0.25 is 1.25mm*2 or 10 amp max?? flex

Another question, if cable is cheaper than TPE flat can it be used as a substitute legally??

The Olex site does have the information: http://storage.baselocation.com/olex...cc65ec42f0.pdf The current ratings for flex are provided towards the end of the document.

Regarding the 'legality', I'm not aware of any explicit ban on using building wire as normal flex cable, however, I'd doubt that it would be deemed to be 'suitable for the purpose' as it wouldn't stand up to the flexing that might be encountered. Also, the TPS sheath is relatively easy to tear.

Having said that, whatever you do past the powerpoint is usually considered your business/problem as far as the regulators are concerned (as long as you are not providing a product/service to someone else).

If you were just using TPS once or twice of the odd welding job, you might get away with it. I wouldn't recommend repeated rolling and unrolling. The copper will harden and break. Also, the standard plugs/sockets are designed for flex and probably won't make good electrical contact with solid (or strand?) building cable.

Have a look at that link I provided above. It shows 2.5mm2 and 4mm2 flex. You should be able to purchase it through a wholesaler. However, you might need to have industrial 56-series type outlets/plugs/sockets fitted to accommodate the large diameter cable (the cost of the cable will look relatively insignificant compared to the cost of industrial fittings ).

Yes , what I was thinking is not the best.
Best practice solution is to get my sparky to install a dedicated line , will have to wait until the new garage is built and then we'll install a high capacity sub-board.

Ta mate!

Hi there, don't know if you know this! but if you weld or draw a lot of current off an extension lead always unwind all of the cable else it will heat up and melt, no matter the size of the cable...

There are many reasons cable is cable and flex is flex mostly it is to do with the way in whitch cable does not flex as eaisly as flex does that said it is much more involved than that.

It has a lot to do with the way it is constructed ever notice how flex has many thinner strands and cable is reasonably soid those little strands combined can handle a lot more current than the cable because of the a skining effect of the electrons essentialy they can move more freely between many strands than fewer solid ones.

you also need to look at its V rating this is the ammount of heat it can handle before the sheath melts. normal house cable is V70 or V90degrees celcius, cheap chinese stuff who knows.

You can deffinately buy heavier cable by the meter that would do the job its sold as orange circular cable we often use up to 10 or 16mm stuff.

just buy a cheap ass generator from bunnings and put a 15 outlet on it.

i would not suggest making your oun cables from flex over about 30mtrs MAX unless you know what your dealing with the heat your experiencing is most likely caused by a drop in voltage whitch causes a higher current whitch causes heat whitch causes higher current then more heat then fire.

oh and if the volts drop too much the circuit breakers wont trip because the current wont be enough to trip them thats my faviourite bit.

Originally Posted by chrisp

Regarding the 'legality', I'm not aware of any explicit ban on using building wire as normal flex cable, however, I'd doubt that it would be deemed to be 'suitable for the purpose' as it wouldn't stand up to the flexing that might be encountered. Also, the TPS sheath is relatively easy to tear.

Having said that, whatever you do past the powerpoint is usually considered your business/problem as far as the regulators are concerned (as long as you are not providing a product/service to someone else).

If you did it in a workplace then you'd be in trouble if an inspector found out, especially so it was done by an electrician (who ought to know better).

But I can't imagine anyone being worried about it if you're using it at home.

Would it be a better alternative to use cable??
If I was to run a "Semi-permanent" extension down to the woodshed then the cost saving of cable over flex is substantial. At the "Great Big Green Shed" I can get cable (2.5mm*2 ) for less than the wholesale price of TP&E

Flex is stranded and gives the ability to be flexable it has many small copper wires which are smaller in diameter tps cable has fewer stands bigger diameter. with what your doing supplying a designated 15 amp supply first you have to work out the distance to know the cable selection you need for ccc (current carrying capacity) you would not use flex for this purpose. You would use two core and earth tps. the depth needs to be min of 600mm deep for the trench for a distance of 20 meters for instance from main board to out let i would use min of 4mm2 but in my opinion 6mm2 would be a beter choice. Even better again use 6mms as sub mains put in a sub board then yo have the ability to install more circuits including lights etc as long as you are not drawing to much current for the cable selected make sure the breakers are the right size and you have rcd protection any electrcian in your area would carry out this professionally and to a high standard I would not recommend carring any elctrical works yourself.
Regards Ben

Hi Ben, I don't do my own hard wiring, but I am happy to do temporary work that is not fixed, sparky is actually coming today (Weather permitting ) and we are running 6mm*2 for the proposed garage.

My question really was theoretical; to allow me to make an informed decision. 4mm*2 flex is hard to find, 4mm*2 cable is easy and cheap; using 4mm*2 allows for voltage drop on really long runs that's all.