Flex for vac.

[PeterC]

Now that the warranty's ended on the Nilfisk vac I want to fit a longer flex. The original flex is only 4m, so I'm having to move the plug at least twice and also can't get far outside. The old Numatic had a 10m flex and that would be an ideal length.

Looking at SF and TS, the 1.5mm TRS seems to be OK, but before I splurge about 10 Wetherspoons beer tokens on 25m (it's typical - SF does 10m on several cables & flexes but not on TRS), is this stuff OK for the purpose?

[Robin]

You could buy 10m and save a few beer tokens- eg

eg

[John Rumm]

or

can be bought by the metre.

[PeterC]

Thanks for that. How flexible is Arctic at non-Arctic temperatures, e.g. 10

- 25C how 'tough' is it cf. TRS. In most places that I've looked, Arctic is more expensive than TRS but on TLC it's cheaper :-)

[PeterC]

That's better. I need the 1.5 as the vac is 1.4kW nominal and has a take-off socket of, IIRC, 1.8kW.

I have ~23m of 1.5 PVC on a reel, but even in this weather it's a bit recalcitrant at times - OK for the garden (the other 27m) where there's room for it, but...

[Robin]

AIUI TRS is more flexible than Arctic at those temps. But I'll defer to anything John Rumm says.

That was my thought and - wriggling - you did mention using it outside ;)

[Andrew Gabriel]

In theory, max length of 1.5mm² extension cable with 13A fuse is 15m, due to earth fault loop impedance. If there's no way to use it without an RCD, then you might argue for a longer one, although it wouldn't pass a PAT test. With 2.5mm², you can go up to 25m, but that won't normally fit into a 13A plug. You can increase these lengths by proportionally reducing the rating of the fuse in the plug.

[fred]

My extension leads of choice here are 1.5mm2 arctic PVC (yellow for visibility rather than voltage ID) and have done me proud for many years. They are long so I hang them in long loops but a quick test at room temp shows that an 8cm loop is a comfortable bend. I wouldn't use them amongst trodden rubble but I have found them to be plenty tough in proper refurb conditions.

In contrast I have an older rubber cabled extension (larger dia as it was made from 4 core 2.5mm2) that I tend to treat more gently as it's flexibility and the fact that it picks up all sorts of stoor when used in dusty conditions make me think of it as more fragile.

Could you drop to 1.0mm2 at that length?

[meow2222]

Most vacs are 2 core, with them in practice any current to earth is going t o be through a higher resistance than the copper wiring. That makes copper R of little effect on current to earth protection IRL. An L-N short may exc eed the recommended trip time, but its not the user thats in circuit, and i t still does the job effectively.

NT

[Andrew Gabriel]

Look back up the thread and you'll see the flex is also effectively an extension lead for a power-take-off, so it can't be 2-core.

[meow2222]

Ah, fairy nuff

NT

[ARW]

Would that 15m not depend on the type of circuit it was plugged into?

A 20A 2.5mm T&E radial circuit will have a more limiting factor than a 32A ring circuit regarding the earth loop limits. Let's assume both circuits are in good condition but the 20A radial circuit socket that the extension lead is plugged into is at it's maximum earth loop reading for the 20A MCB.

[GMM]

It's not much more to scoot down to B&Q for 10m

Oddly enough, I've often found B&Q to be cheaper than Sfx for the same item in electrical supplies, which seems a bit counter-intuitive

[Andrew Gabriel]

Well yes, but you can't make an extension lead which is only safe on some circuits - they will get used on any circuit.

Extension leads are a bit like asprin - if they weren't already invented and in widespread use, they would be banned. It's impossible to design them safely. You can't stop people daisy-chaining them, or using them on appliances which already have max length cables, or overloading them.

What we should have is a wiring rule on the provision of sockets, which exists in some parts of the US. You must be able to plug in an appliance with a 6' lead positioned anywhere around the edge of the room without its flex crossing any doorway. Once you have something like that, there is no need of extension leads in the house for standard appliances. You might still need one for occasional use with portable tools, but most people won't.

[PeterC]

That seems a bit more flexible than PVC. The PVC does tend to form stiffish loops that hook round/under things like fridges,

Yes, rubber does get grotty - it's almost as if it's a bit 'sticky'.

Not with a possible nominal load of 13A, althoughthat would be intermittent.

[PeterC]

I was going to reply to your post re. 15m to say that many leads are over that and up to 40m at 1.5, but this covers that point.

I need the lead from the shed (on RCD) to the top of the garden (hence 27m being just ok and 25m being tight) and then down the other end, so sockets every 12'...!

[meow2222]

True for one semiarbitrary value of safety.

I dont think that would replace my 9 & 12 way leads. Wouldnt even replace the popular 4 ways.

Nor do I think enforcing such a rule very sensible.

NT

[PeterC]

Cheers - I'll pop in tomorrow (wrinklycard day) and see if it's pliable in my hands (then I'll look at the flex). Only £8.42 with 10% off.

[ARW]

But in this case the OP is wanting the to use the appliance outdoors! And everyone with a garden has an extension lead don't they:-)

There does seem to be a difference in maximum lengths allowed. BS 61242 seems to allow 60m for 1.5mm flex. BTW this is outside the scope of my work but I do have a 50m extension lead in the van.

[Andrew Gabriel]

Well, a 13A BS1362 (plug) fuse needs an earth fault loop impedance of no more than 2.42 ohms to clear a short circuit in the required

0.4 seconds. 60m of 1.5mm² flex has an impedance of 1.74 ohms, which is already over 70% of the permitted total value. So it's only safe if the earth fault loop impedance at the socket is