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Old 1st Jun 2018, 10:08 am   #41
Humber888
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Default Re: 13A Twin sockets.

Just had a thought (rare in itself), what about triple gang sockets? We have one in the kitchen used by the refrigerator, microwave oven, plus spare. This socket does have a built-in 13 Amp fuse and hence provides some protection against gross over-current draw, but are all of the 3-gang sockets fused?

Mike
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Old 1st Jun 2018, 10:36 am   #42
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Default Re: 13A Twin sockets.

We have got a fused 3 gang socket in our kitchen too.
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Old 1st Jun 2018, 10:48 am   #43
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Default Re: 13A Twin sockets.

Yes, all 3-gang sockets are fused.

Quote:
" the question arising in this thread is whether a twin 13A socket can handle 26A. Apparently not!" I would say definitely not. Even a quality manufacturer like MK only claims 20A handling.
The crux of this thread is not so much about whether a double socket can take 26A total, but more about whether something that is not integrally protected against operating outside its design parameters can be acceptable under an engineering standard.

As far as whether a socket will overheat at 26A, I would suggest we search for empirical evidence that an actual problem exists with this. They don't, even though the manufacturers may only give a 20A rating. Socket terminals only overheat if the termination is not properly executed, and then they might overheat at a mere 10A. What makes the rating 20A anyway? You can get a terminal that one approval rates at 20A and another rates at 32A according to their specific test methods. The current it will endure in practice depends on so many factors; cable gauge, screw tightness, ambient temp, rate of thermal cycling (a terminal loaded to 20A for 5 minutes in every 10 may fail sooner than one loaded to 26A permanently). By comparison, 45A shower switch terminals, manufactured, rated and approved for 45A, overheat and burn out regularly at 40A. I have no figures but would venture 1000 times as frequently as socket-outlet terminals. That's an actual problem, whereas the socket is a theoretical one. And as per the tests mentioned above, plugs and especially fuse clips overheating at 13A is a real problem.

Moving on to the more fundamental subject of how a device may be legitimately constructed in such a way as it can be pushed outside its approved envelope and operated in a dangerous way, without automatic protection taking over, I would suggest comparison with a car!
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Old 1st Jun 2018, 10:50 am   #44
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Default Re: 13A Twin sockets.

I can't help feel there's a touch of obsessive paranoia revealed in this thread: OK, you *can* overload a dual-13A socket, but IMHO you'd be more likely to overload a 'ring' by having multiple 3Kw loads on the same ring but in different rooms.

The evidence from fire-service statistics is that over the last decade domestic fires have fallen significantly, continuing a trend that was established quite some time back.

See https://www.ukfiretraining.com/news/...downwards.html

This is despite the increase in number of things like 'wall-warts' and other stuff that's left powered 24x7 (microwaves, TVs, PVRs, set-top-boxes, internet routers and the like).

I don't see 'you can take 26A from a dual 13A socket' as being anything for normal people to get their underwear in any kind of knot over: the additional stress caused by worrying unnecessarily about such very-low-probability events is probably more likely to kill you than the event itself!
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Old 1st Jun 2018, 11:51 am   #45
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Default Re: 13A Twin sockets.

Apparently it was not an overloaded wall socket that was the start of the recent tragic tower block fire, where despite the block having a refit a few years ago (where presumbly RCDs etc and smoke alarms were replaced or installed) a low current draw item - the fridge- was the culprit, which obviously didn't trip anything and despite the early signs of a problem-smells,smoke etc was allowed to get to a stage where it was a full blown fire lapping out of the windows and consequently igniting the cladding and the terrible tragedy that followed.
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Old 1st Jun 2018, 12:14 pm   #46
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Default Re: 13A Twin sockets.

Indeed a recent thread highlighted Tumble Dryers and other white goods as a really major ongoing concern, however the power is supplied to the appliance via a ring or other circuit.

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Old 1st Jun 2018, 12:19 pm   #47
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Default Re: 13A Twin sockets.

Quote:
Originally Posted by cheerfulcharlie View Post
Apparently it was not an overloaded wall socket that was the start of the recent tragic tower block fire, where despite the block having a refit a few years ago (where presumbly RCDs etc and smoke alarms were replaced or installed) a low current draw item - the fridge- was the culprit, which obviously didn't trip anything and despite the early signs of a problem-smells,smoke etc was allowed to get to a stage where it was a full blown fire lapping out of the windows and consequently igniting the cladding and the terrible tragedy that followed.
The Grenfell Tower Fire started in a Hotpoint model FF175B Fridge, but let's leave any conclusions up to the public enquiry.

Back on topic please.
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Old 1st Jun 2018, 1:13 pm   #48
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Default Re: 13A Twin sockets.

G6Tanuki - "I can't help feel there's a touch of obsessive paranoia revealed in this thread: OK, you *can* overload a dual-13A socket, but IMHO you'd be more likely to overload a 'ring' by having multiple 3Kw loads on the same ring but in different rooms."

True, but there's a critical difference - if you overload the ring you're protected by the 30A fuse which will disconnect the ring. If you overload a twin socket the fuse won't blow until/unless you draw more than 30A, but you could still be pulling 29.9A through the socket with it merrily melting without blowing fuse!

Not sure I'd call worrying about this "paranoia" - more like common-sense safety. The regulatory system forces us to obsess about earth-loop impedance, sleeving on earth wires, etc, but doesn't seem to have too much concern about a basic issue like this. All rather strange... !

Mike
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Old 1st Jun 2018, 1:22 pm   #49
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Default Re: 13A Twin sockets.

I`d be interested to know how many fires have been caused by an overloaded 13A twin socket compared with the number caused by a single 13A plug running within its rating but with loose connections and or loose fitting fuses.
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Old 1st Jun 2018, 1:56 pm   #50
John M0GLN
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Default Re: 13A Twin sockets.

Quote:
Originally Posted by julie_m View Post
I must admit, I had always assumed that a 13A double socket faceplate could withstand 13A to each outlet-- not just 13A for the whole faceplate.
I've always thought that as well, and just doing a search on a number of websites I can't find anything to the contrary, I'm not saying there isn't but it's not easy to find, I have downloaded a MK file titled 'Wiring Devices Technical' and the only reference to current for their 'two gang' as MK call them is this quote,

"2 Gang Switchsocket Outlet with Integrated
Dual USB Charging Capability

TECHNICAL SPECIFICATION
13A SOCKET OUTLETS
ELECTRICAL
VOLTAGE RATING
220-240V
CURRENT RATING
13A
Combined total 2A drawn from USB outlets"

which makes me think that each outlet is capable of 13A.

John
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Old 1st Jun 2018, 2:15 pm   #51
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Default Re: 13A Twin sockets.

Quote:
Originally Posted by Humber888 View Post
Just had a thought (rare in itself), what about triple gang sockets? We have one in the kitchen used by the refrigerator, microwave oven, plus spare. This socket does have a built-in 13 Amp fuse and hence provides some protection against gross over-current draw, but are all of the 3-gang sockets fused?
The one I have is fused at 13 Amp, most of the time it just has the door bell plugged in, I use one of the sockets weekly for vacuum cleaning, the third hardly ever used. It was fitted so that I could use the spare socket for an oxygen machine, now long gone.

Sensible observation of plugs and sockets without being paranoid about it is all I do, most of us wouldn’t leave a dripping tap or a leaking windows long before fixing it, same with electrical items.
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Old 1st Jun 2018, 2:21 pm   #52
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Default Re: 13A Twin sockets.

@ John MOGLN - "doing a search on a number of websites I can't find anything to the contrary"

Here's an example of discussions of the issue on an IET forum -

https://www.theiet.org/forums/forum/...threadid=33787
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Old 1st Jun 2018, 3:54 pm   #53
John M0GLN
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Default Re: 13A Twin sockets.

Thanks for the link, I had no doubt that there would be discussions somewhere but these are not going to be seen by the vast majority of the population who will be using 13A plugs, the MK two gang sockets described in their 'Wiring Devices Technical' file have 4 references to the current supply capability of the USB sockets but strangely none regarding the 13A sockets except that they are 13A.

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Old 1st Jun 2018, 4:23 pm   #54
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Default Re: 13A Twin sockets.

Interesting that the times quoted in MK's own stress tests are inconsistent with the assumed conditions for thermal stability in the official test.
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Old 1st Jun 2018, 4:40 pm   #55
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Default Re: 13A Twin sockets.

@ John MOGLN - Also interesting that in that IET link (from 2009) there seemed to be general ignorance of and/or lack of concern about the issue amongst the forumniks (some or many of whom are probably professional electricians). I do wonder how many professionals are aware of it even today... And the same old arguments about "hardly ever going to happen", and "don't worry about it".
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Old 1st Jun 2018, 4:44 pm   #56
G6Tanuki
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Default Re: 13A Twin sockets.

Q: Can you produce any evidence from a credible source (Fire-service, Home Office, insurance industry) that this 'issue' has ever been attributed as the cause of a fire or significant injury to property or persons?
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Old 1st Jun 2018, 4:53 pm   #57
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Default Re: 13A Twin sockets.

No, I wouldn't know where to look. And I'm not sure whether such reports provide that level of detail - maybe they just give the cause as generic "electrical fault". Others may know.

But, I keep reminding myself that being able to pull up to 26A out of a 13A-rated unit is fundamentally a "bad idea". And, as I've said, given the detail and rigour of most of the other regulations, the overlooking of this problem is extraordinary.
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Old 1st Jun 2018, 5:19 pm   #58
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Default Re: 13A Twin sockets.

13 Amp sockets and spurs are designed to comply in the first instance to BS1363. Reference should be made to this standard to find out the design, test and load criteria.


Does anyone on here have access to this document? Perhaps it might give some definitive answers.


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Old 1st Jun 2018, 7:59 pm   #59
Dai Corner
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Default Re: 13A Twin sockets.

You can buy a copy for (are you sitting down?) £254

https://shop.bsigroup.com/ProductDet...00000030365274
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Old 1st Jun 2018, 8:56 pm   #60
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Default Re: 13A Twin sockets.

...Having to buy the 18th Regs book next month at around £80 is bad enough. I think I’ll give it a miss.

That’s why I was hoping someone here would have access to a copy��


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