2.5mm T&E or 6mm T&E?

[CC45]

Dear all,

Some years ago I bought a gasless MIG welder - but due to an admin error (mine unfortunately) I bought one with a 16A plug like this not the normal 13A plug.  I regret this but don't want to spend another £250 getting a replacement so I am about to sort out a female 16A plug so I can use the welder I've got.  My query is this - can I safely use 2.5mm T&E to supply it?  I think I can since the RCD is rated at 16A - why do this if it can't handle that.  I am happy to buy some 6mm cable but I've got 2.5mm to hand.

Any thoughts?

Cheers

CC

Edited July 15, 2016 by Nickfromwales
Typo

[ProDave]

2.5mm will, under the right conditions, withstand up to 27 amps, so will be fine for 16A.  The only thing to watch for is voltage drop, if it's a long run you might consider 4mm.

P.S an RCD is a residual current device, to trip in the event of earth leakage. It is rated usually at 30mA. What you need is an rcd and a seperate mcb rated at 16A, OR an rcbo, which is an rcd and mcb in the same housing.

[CC45]

Thanks Dave.  Its going to get wired into my current consumer unit - length is ~ 2m so I don't think that will be a prob.

Appreciate the reply.

CC

[Jeremy Harris]

FWIW, one of my car charging points is a 16A one, around 4m from the outdoor consumer unit and RCBO, and that's on 2.5mm² SWA, in fact I could have got away with running it on 1.5mm² SWA quite safely at the maximum continuous power of around 3.7 kW, with a voltage drop of just under 2V.

2.5mm² is a massive overkill for my car charger, but I happened to have a spare left over length, so used it.  It does mean I could upgrade that charge point to around 8.3 KW in future if I needed to (around 36A with a 2.74 V drop at 230 V).

Most cables are capable of carrying a lot more current than people might think, especially in short lengths.  As Dave says, it's almost always voltage drop that determines the cable size used, not the cable maximum current rating.

If you want to know the cable size and voltage drop for any given cable type, length and load, there is a useful calculator on the TLC website (in fact there's lots of useful information about wiring regs on there too).  This is a link to their technical section:https://www.tlc-direct.co.uk/Technical/index.html

And the cable voltage drop and size  calculator is here: https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

From that you can see that your 2m length of 2.5mm² T&E, clipped to a wall, with a room temp of 25 deg C, will work at it's max current rating of 27.8 A (6.39 kW at 230 V) with a 1V voltage drop.  For a max current of 16A, then you would be safe with 1mm² T&E over 2m, believe it or not (not that I'd recommend it!).  With 2.5mm² T&E  you could run a length of up to 40m and still just be just on the 5% voltage drop limit.

[CC45]

2.5mm used - did some welding - all fine.  Thanks for the advice.

 

CC