Overheated extension reel

[cwhaley]

This is the sort of stuff that should be taught in schools. There might be warning labels on extension cables but they usually assume some basic understanding of amps, watts etc. that not everyone has.

I think it is taught in schools. I remember being taught in physics how to wire a plug (not sure why it was covered, but it was part of the curriculum for that subject). Our old teacher Mr. Hunt also told us (and explained very well as I remember) about the difference between amps/currents and volts, the functions of fuses and why wires are rated for different currents. This was secondary school between 2001 to 2006 -- I can't imagine it's changed much. As with most things taught at school, however -- most of it isn't retained!

I genuinely think 'home economics' should be re-taught. The value of teaching life basics at a universal level must be very high.

I will agree with @johnny2007 though, the instructions could be more prominent. My reel has a thermal cutout, but the warning about un-wound / wound ratings is moulded into black plastic on the rear of the unit.

 

[Chainsawcharlie]

You just made a capacitor

 

[Ragnar_AT]

You just made a capacitor

In theory yes, I'd assume the capacitance is negligible though. The most important factor is the resistance of the wire and the lack of heat dissipation if the flex is wound tightly onto the reel.

 

[Millwright]

Aren‘t UK reels required to have a thermal cutout? I haven‘t seen a new reel without one on the continent for a long, long time.

Yes most if not all new reels have a thermal cut out, for normal use. This won't take into account the heat in the cable of a wound reel, as the thermal cut out is for the heat dissipation from current draw with the reel being used as designed. The current draw here was fine, but the cable being wound reduces the dissipation of the cable, the thermal cut out doesn't know that the cable is still coiled.

 

[Harry Bloomfield]

The current draw here was fine, but the cable being wound reduces the dissipation of the cable, the thermal cut out doesn't know that the cable is still coiled.

Those reel cut-outs I have examined, would generally 'see' the heat from the coiled cable, that is the whole point of the thermal cut-out..

 

[Justin Passing]

You just made a capacitor

Inductor! Twin cable is already a capacitor. You made a tank circuit.
So it'll have a resonant frequency, f = 1 / (2π × √(L × C)). Very poor Q though, because R is significant.

 

[Diver Fred]

My wife and I ran a B&B until recently. You quickly realise that many people simply don’t read anything.

We had a saniflo toilet in one room, we had two notices telling people to be careful what they put down the loo but to no avail. I lost count of the times I had the thing apart cutting off sanitary towels (or worse) wrapped around the cutting blades. Lovely!

Used to regularly holiday on an onshore cruise boat,12 punters max with 2 crew. One week there was a gentleman in the party who had led, say we say, an adventurous life in the company of other gentleman... We discovered, mid trip that he couldn't read as one or both of the 'electric' toilets would fail every morning - after the skipper had sorted the problem for the third day he asked who was disposing of tampons down the toilets; it turn out be not one of the girls on board but this chap whose sphincter muscles had effectively lost their ability to close completely, he used tampons as a form of plug.
He either had ignored or didn't understand the 'do not dispose' notice.