Warm! 13 amp UK style plugs etc.

[terry]

Presently visiting Mddle East and need to ask someone familiar with the UK style 13 amp fused plugs, 230 volt at 50 cycles etc. the following question.

It's been unusually chilly and neighbours using electric heaters have used what it is understand are called 'Power bars' each with or without switches, some small indicator lamps/neons and several outlets. Due to poor quality (possibly made in some people's republic?) a couple of these have caught on fire! Fortunately without damage etc.

So instead we recently wired up some substantial single outlet extension cords using brand new allegedly UK made 13 amp plugs, 2.5 mm three conductor cab-tyre cable to a single three prong outlet mounted in a plastic approx four inch square box. All material was brand new.

All connections are new and good, the stranded wire ends being tinned with solder and secured tightly under those little brass screws. Arrangement made to avoid any chance of pulling the wires by double tie clamping the rubber cable sheath to the box. The 13 amp fuse holder is tight and new.

Testing one extension, about 8 feet long, with a 2000 watt small blower heater surprised to find the plug getting 'quite warm' but not hot after a couple of hours! This normal?????? The wire 'cord' is not the least warm to the touch.

It seems to be mainly the plugs that are getting warm; each plug has a solid brass earth/ground pin. The neutral (Blue) and live (Brown) pins are partially brass and partially brown plastic. They look exactlty like all other 3 prongers used for 230 volt here.

So 2000/230 = 8.7 amps; load mainly resistive with a few watts for the fan blower. So well within the 13 amp rating; eh? One reason to ask is that in North America we routinely take up to 1200 or 1500 watts (at

115/120 volts = approx 10 amps) through North American style, unfused, three prong plugs that appear to be less substantial and contain less metal etc. than the UK version. And I don't recall they (normally) get warm. Unless they or the outlet is faulty.

Any comments/advice please?

[Bob Minchin]

Sometime the connection to the fuse are poor. Avoid the type that have a pair of prongs (like part of a table fork) at each end of the fuse. The fuse caps are sivler plated and may have become tarnished. Try cleaning these. Finally the fuses themselves can run a little warm. The plug body may become warm and if it the fuse then the live pin will be warm by the neutral pin should remain cold. Bob

[jrwalliker]

It is best to avoid "tinning" the wire ends with solder. This is for two reasons. Firstly, solder has a higher resistivity than copper, so the temperature rise may be higher. Secondly, when the joint is subjected to temperature variations, the solder deforms because of a difference in temperature coefficient of expansion between the different metals and the contact pressure gradually diminishes. This results in an even higher resistance causing even more heating...

"Slightly warm" would be reasonable after a few hours, but certainly not "hot"

John

[Andy Champ]

Are they marked BS1363a?

It occurs to me it could be the pin-socket connection, not anything inside the plug. The heat would run up the pin.

Andy

[Andrew Gabriel]

I would strongly suggest not using heaters on extention cables or multi-way adaptors. Plug them into the wall socket directly.

Many of the multi-way adaptors and extention cords you find in the middle east are appauling quality and are not permitted in the UK.

You should never tin the stranded wire ends. The solder will creep and result in loss of contact pressure and a poor connection. Cut that off and remake the connections.

The BS1362 fuse will give off up to 1W at rated current. That's normal (and part of the spec).

BTW, I often find US plugs hot, and the cable warm.

[Dave Plowman (News)]

Not recommended or needed.

[terry]

=A0 London SW

The following morning; many thanks for the replies. Very knowledgeable and useful discussion. The advice to 'not' tin the ends of the wires especially interesting; thank you. Will reterminate, have enough slack to do so. Am always worried about those brass screws being so sharp as to cut off individual strands? That a BS fuse can dissipate some one watt is good info. Cos that's probably about how much 'warmth' I was feeling after a couple of hours of hot testing last evening. Must agree that the quality of much of the electrical here (and some of the workmanship!) is what some might consider appalling. Fortunately the living units are constructed of concrete block, with hard tiled floors etc. The only wood around (unlike North America) homes is in the doors and and door frames. Even the window frames are of metal, with single glass. Last night lying in bed the curtains were moving and it wasn't even windy; nothing like a good Nor'easter at minus 14 Celsius off the North Atlantic am used to back home, gusting to 100 kmh! The situation of neighbours is that wall outlets are infrequent (probably on one ring main per floor), each single outlet is switched. Nothing like the every six feet, with a limit on the number of duplex outlets on each radial 'run', that one is used to. (Just a minute while I bang on the presently not in use wall mounted AC unit to scare away birds trying to roost on it outside! Hope they don't have bird flu!). And the el cheapo (made in Mexico, Guatamala, or India etc. heaters have short cords with sometimes doubtful plugs and (on a 2kw heater for example) wires that look plastickily heavy but maybe have 18 AWG wires inside? Maybe tack welded to the heater element. Although peering into one it does seem to have an over-heat 'diode-thermistor' in series with the heater coil. No 'tip-over' switch though. Anyway; to avoid heaters with short leads getting tucked in behind furniture, individal single outlet extensions out into open floor space is we think the safest answer. Better'n than those 'power bars' especially the ones supposed to accept three or four kinds of plugs, Shuko, UK 3 prong, even NA three bladers! Also and btw, power converters! On 230 volts no less. Lets see twice the voltage, twice the current, four times the power and its 50 hertz not 60, so some power converters/adapters indeed go 'poof'! e.g. A discussion with someone with two degrees and no technical thoughts whatsoever! "And how many power bars have you had burn up, only two you say ..... Well you've been lucky then! And where did you buy those? Ah yes Almhedi souk for only ten riyals ....... I see. And they just melted, eh?. Hmm! Plastic stuck to the floor tile?" My son; it's a different world! Cheers.

[Rod]

A while before fitted plugs became mandatory, many of the electrical appliances I bought had tinned wire ends as new. Can't remember where from, but someone advised me to cut them off - as is the advice here. But odd that companies selling the products could supply them in that state to customers who would in general leave them like that (I assume - seems obvious to do so to the ignorant like I was).

(Seems that the companies did that to make some part of testing easier/safer for workers and just left them like that for sale.)

[Frank Erskine]

Most of the tinned ends had to be trimmed off anyway to fit the plug properly :-)

The tinned ends were probably of use to the manufacturer for attaching crocodile clips for testing.

[geoff]

I have heard this said before - and have seen others argue against it.

I accept that theoretically you may well be right - but can you back it up: has this "theory" ever been tested or proven?

[Rod]

Agreed - but didn't that also coincide with "equal wire length" plus being quite common? Which meant you didn't need to trim them.

[The Natural Philosopher]

Not croc clips. IIRC they are called SafeBlocs. Ideal for safe tempoary mains connections. Still got one somewhere.

On te solder thing, yuou get more surface arra frona squished solderedful wire, so te contact resoistance is probabltyu better.

The main reasin to discard is that the solder stiffens the wire and leads to a stress concentration. Any wiggle in the flex and one day the wires snap till theres only a few strands that get bloody hot and catch fire, or fuse and arc..

[Paul D.Smith]

...snip...

It wasn't clear which plug was getting warm, the one plugged into the wall or the one plugged into your extension. If the latter, then see answers below. If the former, have you checked the wall socket? It could well be the socket getting warm and you're feeling heat conducted into the plug.

FWIW I have a 2kW kettle and it's plug doesn't get warm.

Paul DS.

[terry]

=2E Thanks again. The slightly warm 13 amp plug (plugged into the wall outlet, which is itself of unknown origin!) IS marked BS1363; moulded into the plastic, along with what looks like other 'standards'. But the stick-on shop bar code label on one of the several plugs bought, to make up three extension, says 'Made in China'! So while they 'appear' to be of good quality ...... ? The cost here was equivalent to about 1.30 UK pounds, new. So that may be the whole story of a plug getting warm with less than 9 amps! Also accept, as suggested, it may be the outlet with heat conducted up the pins! Anyway not going to change wall outlets in this rented premises; unless it burns up/hazardous and then will probably have to do it ourselves to continue service, rather than wait weeks for action!!!! Another difference may be that a kettle (Hey I like that fast warm up of a 2 kw. 230 volt kettle, versus the common 115 volt 1200 watters of NA!) is only in use for a few minutes; whereas a small 2 kw.heater may be on for several hours? Again thanks for sharing all the info. Always learns sumptin, eh?

[Paul D.Smith]

...snip... Thanks again. The slightly warm 13 amp plug (plugged into the wall outlet, which is itself of unknown origin!) IS marked BS1363; moulded into the plastic, along with what looks like other 'standards'. But the stick-on shop bar code label on one of the several plugs bought, to make up three extension, says 'Made in China'!

PDS> I wouldn't read much into that. There is hardly any manufacturing left in the UK now so a UK certified plug being made in China would not be too surprisingl.

Another difference may be that a kettle (Hey I like that fast warm up of a 2 kw. 230 volt kettle, versus the common 115 volt 1200 watters of NA!) is only in use for a few minutes; whereas a small 2 kw.heater may be on for several hours?

PDS> Granted - I have to admit to having thought of that myself, just _after_ having hit "send". I'd heard that electric kettles were available in the US now but didn't realise they were so whimpy. As a Brit who travels to the states, using a stove-top kettle is like stepping back in time to my grandfather's kitchen ;-).

Paul DS.

[Mike Clarke]

Mike Tomlinson posted here a couple of weeks ago with details of problems he'd had with tinned wire ends, along with links to some photos of the damage.

[Dave Liquorice]

A 2kW kettle is a normal slow one. Rapid boil ones are 3kW...

This is true and TBH a *slightly* warm plug with a 2kW heater on it for several hours I wouldn't be too worried about. The problem is what is "slightly warm" to me that would be above room temp but not above body temp somewhere about 30C to 35C, rather than not quite hot but more than warm bath in the mid 40's C.