Hot plugs

[Andy Bennet]

Thinking about it you probably need to replace the mains lead on your heater. One of these seems quite suitable - just cut the plug off the other end and replace.

[Roger Hayter]

And that is sufficient justification for one decimal place in expressing the average/median, whichever it is. Actually a precision of about a quarter of a Fahrenheit degree would probably be sufficient, but is hard to express in our number writing system.

[Roger Hayter]

UK fan heaters are all single phase. (or just possibly three phase in an industrial context.) No 120V mains supplies.

[Bruce Farquhar]

When something varies by 3.6 you don't quote it with a decimal place. Imagine you had a dodgy analogue meter which had a shaky needle. The readout varied between 52 and 55.6. You wouldn't read it as 53.8 would you? That implies some accuracy. Saying we're 98.6 will make some people think they're ill when they read 99.

[Bruce Farquhar]

Why would that make a difference? And anyway it's not really 2 phase in our US home. It's single phase, split.

[Bruce Farquhar]

We can be thankful for a lot less wiring.

[Bruce Farquhar]

Sounds a bit overkill, I'll just make sure high current devices get polished if the prongs aren't shiny.

[Bruce Farquhar]

The lead is fine. It's not overheating now I cleaned the prongs.

[NY]

I've done that before now with the plug for a 3-bar (3 kW) electric fire, when I smelled the plastic of the plug getting a bit hot. The live pin was actually too hot to touch (*). I removed the plug, took out all the pins (having dropped the live one in cold water to cool it down!) and used fine sandpaper on a flat surface to polish the four sides of each pin until they were shiny.

If I see a high-current device with a removable plug that has oxidised pins, I remove them and give them the sandpaper treatment. Sadly you can't do that with moulded-on plugs, and trying to polish them in situ is very hard.

(*) I think the screw that attached the wire to the pin may have been a bit slack, so there may have been a bit of contact resistance there as well. I always check that the exposed bit of wire that goes into the screw hole seems to have about the right thickness of strands and some haven't broken off - assuming it's stranded rather than solid wire.

[Bruce Farquhar]

Get a fibre glass pencil. Handy for oxidised battery contacts too. I polished my heater's prongs without removing them.

[Martin Brown]

They actually use brass. But the contacts are designed to be self cleaning but are not always as bright as they might be. By far the most common cause of a hot plug is actually a loose wire inside it.

However, at this time of year when elderly relatives are running 3kW fan heaters full bore that have stood idle for the best part of a year it is worth keeping an eye out for plugs that get mad hot.

3kW on a kettle isn't too bad since the load only persists for a couple of minutes but a 3kW fan heater on in a cold room could run for a couple of hours before it first cuts out. Plenty of time for any weak connection in the plug or socket to get mad hot. You know you have a very serious problem when one or other starts to melt or char.

Plugs on powerful heaters need to be checked periodically because you are running them very close to their design limits and things can gradually work loose over time.

ISTR that the recommended maximum load for portable appliances has been dropped to 2.4kW in the not so recent past but there are plenty of 3kW fan heaters still around especially in the homes of elderly people.

[Tim Lamb]

My 2 pennorth... I understood the socket contacts are a hardenable alloy. Beryllium/Copper? and that excess heat (poor contact/high current) anneals them back to soft, leading to further poor contact issues.

[Martin Brown]

That is correct - the fuse contacts are usually beryllium copper springs. I have never known them denature except in a plug that has been seriously abused with 30A or more flowing for tens of minutes. The fuse itself gets very hot internally close to melting point at this stage.

All bets are off if there is a bad connection somewhere.

[Bruce Farquhar]

Bullshit. Humans are warm blooded and don't need a nice steady ambient temperature.

[Bruce Farquhar]

I hope that doesn't apply to kettles or they'd take longer to boil.

What's the point in having plugs and sockets designed for 13A if we can't use it all? They should be designed better in the first place.

[Vir Campestris]

<fx fondles plug on fan heater>

Ah.

On closer inspection the live has almost pulled out of its terminal :(

(My dad evidently did what I do - make it up so if the cable is pulled the live disconnects first)

Thanks for the reminder.

Andy

[Bruce Farquhar]

It's odd that Americans have so many regulations about electricity, yet have such a pitifully dangerous and useless system. Or maybe that's WHY they have all those regulations, er sorry "codes". I do detest them using the word "code" - a code is something you'd use for encrypted communications.

[Bruce Farquhar]

I've seen those come loose or even rot away.

And of course it depends how hard it's yanked. A lot of Americans actually just pull plugs out by the cable, since they have the flex coming out of the front. They claim this means they come out of the socket in case of a problem, like you trip over the flex, but then if it gets half knocked out you get resistance....

[Bruce Farquhar]

When the device goes off due to the neutral coming out first, you'd stop using it anyway.

[Troll Buster]

Oh, you got codes too.