How many 2.5mm T&E into a 13A socket?

[Alexander Lamaison]

So now this apocalyptic socket is running at 600C?

Alex

[John Rumm]

If you use 1.00mm (the smallest you could use), then you need to take more care ensuring it does not get buried in insulation since that will reduce its max load to around 8A, which does not leave much room for any additional derating factors with a 6A circuit.

You also need to watch your circuit lengths a bit more as the PSSC will rise.

Personally I am happy to use 1.00mm^2 T&E on many lighting circuits, however you need to assess more carefully when to switch to the larger size. If doing the work professionally, it would probably make more sense to default to 1.5m to save needing to carry more cable sizes.

On a one off, material cost would matter less. However that would not encourage me to use 2.5mm^2 on the lighting circuit for other reasons.

On a shower its a fair comment - the smallest you could get away with would typically be 6mm^2. While its slightly easier to work with than

10mm^2, they are both are a pig - so you may as well allow more future shower options with the larger size.

The argument does not extend to wiring lights with 2.5mm^2 cable as your previous post seemed to suggest.

Same would apply to using the "right" size.

Doubt the extra weight makes much difference...

Tim has covered the point about stresses on terminals etc. There is the additional point that you may think you have pushed a cable "home" into a terminal when in fact you only have a grip end the very end of it due to an overstuffed terminal.

[John Rumm]

Unlikely on both counts...

They are assuming you will use an average of around 8A

Your fuse won't blow at 100A (unless its a 40A one)

Just as well no one makes that assumption then.

[Tim Watts]

On Tuesday 02 April 2013 19:41 Major Scott wrote in uk.d-i-y:

You fuckign well should be - you are required to meet the 0.4second disconnection time, with an overcurrent device. The type of device is irrelevant.

Don't bother replying, there will be no further debate on this point.

[Tim Watts]

On Tuesday 02 April 2013 22:07 Major Scott wrote in uk.d-i-y:

Yes. And?...

[Major Scott]

It's a good guide. You wouldn't use lighting wire then fit a 30A fuse. In a portable appliance you don't fit a fuse higher than the flex is rated.

[Major Scott]

Yes I know, but it'll stop me consistently using too much which could damage other components.

If I use too much electricity on my ringmain, the fuse should blow before the wire catches fire.

[Major Scott]

At least someone is doing it properly. So if you all think 20A is ok, w= hy do you think MK is testing at 26?

A tumble dryer draws full power continuously unless you select the gentl= e low heat cycle.

A few dozen is a bit much, this house probably has 16 (2 bedrooms). Any= way, I bought my (brass) double sockets for =A33 each. I assume 26A ins= tead of 20A would make them maybe =A33.50 each. That's =A38 extra.

=A38 per house...... less than a tin of paint.

Some people are not.

-- =

Mick and Paddy are reading head stones at a nearby cemetery. Mick says "Crikey! There's a bloke here who was 152!" Paddy says "What's his name?" Mick replies "Miles, from London!"

[Alexander Lamaison]

It should be a guide. The problem seems to be you're using it as a rule and ignoring what the regs actually say.

Alex

[Major Scott]

They'll get a bit hot though, and the contacts will wear down.

Or get an MK.

It should eventually, or why call it a 20A fuse?

Surely 6A extra isn't going to change the price by much. You've still g= ot the same amount of most of the materials.

-- =

Joey's teacher sent a note home to his Mother saying, "Joey seems to be = a very bright boy, but spends too much of his time thinking about sex an= d girls." The Mother wrote back the next day, "If you find a solution, please advi= se. I have the same problem with his Father."

[Major Scott]

I've got copper heating pipes in my airing cupboard that get that hot, and I don't much like bottles of stuff being against them.

[Major Scott]

Say there's a bit where the heat can't escape and will build up...

[Major Scott]

A few decades ago, it was all we had. They worked fine.

[Major Scott]

Actually paper ignites at 233C.

[Alexander Lamaison]

MK's USP is to go that extra step beyond what's required in order to justify their price premium. Otherwise you'd you'd buy a cheap asian import, as all (legal) manufacturers meet the minimum spec.

13A (domestically, usually less) for a couple of hours. NBD. Even with the dishwasher and washing machine elements occasionally joining in.

Although your argument sounds good, the proof is in the pudding. If it made financial sense, more manufacturers would make their double-sockets exceed the standard. But they don't, so it doesn't. Simples.

Alex

[Alexander Lamaison]

Cry me a river.

Good question. I think a 20A (non-rewireable) fuse is called a 20A fuse because it can provide overload and fault protection for those circuits with a design current of = 20A. But that cable rating of >= 20A already takes into account the fact that the fuse doesn't even think about blowing until about 30A so all is well.

And just because it provides overload protection for circuits with >=20A cable rating doesn't mean it can't provide fault protection for cables with = 20A. Well, ok, it is, but that's basically because they hacked the regs to make the use of a rewireable fuse a cable derating factor. This forces it to realign again. Why didn't they just rate them 0.725 lower in the first place?

Alex

[Major Scott]

A ring main can be 40 amps of cable (2 x 20A). 8/6 isn't much different= to 40/30, in fact it's identical. I suppose that doesn't usually go un= der insulation though.

If I was going to add one light and had some 2.5mm^2 cable to hand, I'd = rather not bother driving to B&Q.

They must have a finite life, mind you that might be mor than the house = bricks :-)

Har har....

That's why I give them a tug after I've tightened them.

-- =

Peter is currently listening to 10 minutes of laughter set to music.

[Alexander Lamaison]

You mean like insulation? Then your cable has to be appropriately derated. Of course heat can't build up indefinitely so a cable surrounded by insulation is 'only' derated by half.

Alex

[Alexander Lamaison]

Because the people who installed them a few decades ago made sure there was an adequate PFC to blow them!!

[Alexander Lamaison]

450C actually [1], but who's counting? And I was talking about the match. [1]

Alex