Why don't lamps come with a 1 amp fuse in the plugs?

[JohnW2]

My comments were nothing to do with 'what is stated on the product' but, rather, were a response to Simon's apparent suggestion (at least, implication) that the connectors being rated at 10A was a reason for having a 10A fuse.

Did I ? I think the question was why a lead might be labelled as 10A when it's got cable rated for a 13A fuse. If one of the connectors is only suitable up to 10A then it would seem reasonable for the lead to be labelled as a "10A" lead.

Fair enough. The question actually asked why a 'kettle lead' should be 'rated' at 10A if it had 1.5mm² cable, and your response was to point out that the connectors were only rated at 10A (for whatever reason ). I suppose that my mind then did some extrapolating, and presumed that you would think that, if the lead (connectors plus cable) was only 'rated' at 10A, it would be irrational for it to have a fuse greater than 10A - although I have to agree that you didn't actually say that. My apologies.

Kind Regards, John

 

[JohnW2]

But none of any of this changes the fact that IEC60329 C13/14 connectors are rated at only 10A, which is why the makers of pre-formed leads state that rating on their product.

... and various similar things. Is it just my computer, or browser, or are other people experiencing the phenomenon that anything put in italics in a post is currently showing up as 'blank' (just 'white space') on their screen? In other words, what I am seeing on my screen in the above quote is (with dashes representing the 'white space') "... connectors are ----- at ---- 10A, which....".

Kind Regards, John

 

[JohnW2]

I don't think anyone has really come up with an explanation as to why (given Table 4F3A of BS7671) that Table seems to indicate that that it is acceptable for 0.75 or 1.0 mm² flex to be protected by a 13A fuse.

Because that table describes test conditions, and since 3A is the only other preferred value for BS 1362 fuses,

Fair enough - that makes sense.

Mind you, Table 4F3A itself seems to indicate surprisingly low CCCs for flexible cables - e.g. 10A for 1mm² flex, as compared with 17A for 1mm² T+E in free air (Method E).

1) That table is for cables operating at 60°C, not 70.

True - but that 10° difference would presumably only account for a very small difference in CCC.

2) You don't have the possibility of T&E (used correctly) supporting a mass of 5kg. It would seem reasonable that mechanical stresses on cables with insulation softened by running at 70°C might be a problem.

Yes, that is obviously a factor - but I'm still rather surprised that there is such a difference in the stated CCCs. However, I suppose that consistent with that explanation is the fact that the difference between CCCs of flex and T+E gets much smaller by the time one gets up to 4mm².

Kind Regards, John

 

[SimonH2]

Is it just my computer, or browser, or are other people experiencing the phenomenon that anything put in italics in a post is currently showing up as 'blank' (just 'white space') on their screen?

It's working fine for me.
Try selecting all the text - sometimes it looks different when highlighted. Otherwise, try changing the default font and see if that helps.

 

[JohnW2]

Is it just my computer, or browser, or are other people experiencing the phenomenon that anything put in italics in a post is currently showing up as 'blank' (just 'white space') on their screen?

It's working fine for me. Try selecting all the text - sometimes it looks different when highlighted.

Ah! Thanks. What I've been seeing is:

Untitled

• JohnW2
• 10 Jan 2015
• 1

... but if I highlight it, the italic words magically appear:

Untitled

• JohnW2
• 10 Jan 2015
• 1

... but I obviously don't want to have to do that every time, so...

Otherwise, try changing the default font and see if that helps.

Ill give that a try. However, I certainly haven't changed the font recently, but this phenomenon has only appeared in the past few days.

Kind Regards, John

 

[ban-all-sheds]

I don't think anyone has really come up with an explanation as to why (given Table 4F3A of BS7671) that Table seems to indicate that that it is acceptable for 0.75 or 1.0 mm² flex to be protected by a 13A fuse.

Because that table describes test conditions, and since 3A is the only other preferred value for BS 1362 fuses, if you want to test a pre-wired plug & cable rated at 6 or 10A then you have to use a 13A fuse.

As long as you don't notice the reference to 5A fuses that explanation is perfect. But even if you admit the existence of 5A fuses you'd still need 13A ones to run tests at 7A or 11A.

Right.

This is wrong.

I did indeed think that Table 2 specified the fuse ratings to be used in the tests. Seemed perfectly reasonable - I didn't look on it as "implying" anything, or think that I was drawing any inferences. If you want to test a plug+lead rated at xA then you ought to put > xA through it to check that it's not a fraction away from exploding at its rated current, if for no other reason than allowable supply voltage excursions could cause a load to exceed the rated current.

And it seemed reasonable that the test should be done under realistic conditions, which would include a fuse in the plug.

But no - for the plug temperature rise test the fuse is replaced by a calibrated link which dissipates between 0.95 & 1.0W at 13A.

Memo to self - RTFM.

 

[JohnW2]

Right. ... This is wrong. ... Memo to self - RTFM.

Thanks.

Kind Regards, John