double socket amps

[JohnW2]

Nonsense from you. Read https://www.google.com/url?sa=t&source=web&rct=j&url=https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=33787&ved=2ahUKEwjA74y93PHiAhUkrXEKHUdoCrMQFjAKegQIAhAB&usg=AOvVaw327ABdYfgJWezdekFCEouQ&cshid=1560816114440] this [/url]

It's not nonsense from me in terms of what the MK Technical Data Sheets have said for very many years (at least 10 years - see below). As I have said, although what they have written is potentially ambiguous (and MK Tech Support can't clarify that issue!), there are only two possible interpretations - that the total 'rating' of a double socket is either 26A or 13A (and, as EFLI and I have both said, the latter seems pretty unlikely).

As for your link, we have often discussed the quote from MK which appears within that thread. As you have shown, it appeared in the IET forum 10 years ago and, even then, no-one knew where the MK quote had come from - and people were saying (as you can see if you read that thread) that, even then, the stated 'rating' of MK sockets was, at that time, exactly as it is today (i.e. 13A "per socket outlet"), even though that material (presumably from MK at some point in history) said ...

All MK socket-outlets are manufactured to comply with BS1363 part 2: 1995 and are rated at 13A per unit. Double socket-outlets have been manufactured and tested to exceed this rating by margin that allows electrical safety and reduces the risk of heat and mechanical damage to components due to overloading. It should be noted that BS1363 part 2: 1995 does not allow double sockets to operate at twice the permissible maximum loading and it should be remembered that double socket-outlets are not manufactured to be able to withstand a 26A load for sustained periods of time.

Research by ourselves and third party organisations has shown that all MK double sockets can safely withstand a continuous load of 19.5A for an indefinite period. Increasing the load slightly will begin to cause heat and mechanical stresses on the components in a relatively short period. Testing showed that a load of 22.3A was sufficient to cause heat stress that would cause a browning of the faceplates and sufficient heat to cause insulation damage to cable cores. A load of 24A for 43 hours was sufficient to cause significant heat damage to the material in which the socket-outlet was situated and within 75 hours sufficient to cause significant damage that would lead to the very real potential of fire.

MK recommend that users of their sockets consult professional design Engineers when designing installations to avoid the possibility of heat and mechanical stress to components and installations caused by overloading of MK socket-outlets.

Kind Regards, John

 

[EFLImpudence]

Nonsense from you. Read this:

It even quotes something from one of the schemes - yeah, that's definitive.

 

[bernardgreen]

The way I see ir is that the description " 13 amp " comes from the maximum current that the plug and socket are able to carry. Perjhaps better to call it a "max 13 amp" plug. But decades too late for that to happen.

Has anyone seen a double 5 amp socket or a double 15 amp socket. ?

So why did the double 13 amp socket come into being. Could it be that the 13 amp plug could be changed to a 3 amp plug by changing the fuse fitted and hence one 13 amp sockt could be replaced by a double socket for a pair of 13 amp plugs that had fuses of less than 20 amps total. And two sockets with one plug each is better that one socket + adpator and 2 plugs

Why not rate the double socket at 26 amps.

Would anyone require 6 kW of power in a small area ? Other than a washing machine and a tumble drier next to each other the answer is almost always no. So a double socket that can sarry 26 amps is not going to be common item. ( other than the washing machine + drier situation )

So maybe the regulations were written with that in mind ( and assuming two single sockets would installed for the washing machine + drier situation.)

The weak points in any plug and socket are where current passes from one piece of metal to another piece of metal. The contact between pin of plug and spring of socket is widely recognised as being a weak point. The connection between cable and terninal is also a weak point but very often it is not recognised as a weak point by installers. It does have a contact resistance and as such will develop some heat when current passes through it. The design of the socket has to be able to conduct that heat safely way from the terminal. Production costs would lead to minimum metal and this would lead to adopting the lowest current that the regulations required which is 20 amps.

 

[JohnW2]

Has anyone seen a double 5 amp socket or a double 15 amp socket. ?

I don't recall every having personally seen one, and it's very possible that they were never available/used in the UK - but if you ask Mr Google about this, you'll find plenty, of which this was the first he told me about ...

Why not rate the double socket at 26 amps. .... Would anyone require 6 kW of power in a small area ? Other than a washing machine and a tumble drier next to each other the answer is almost always no. So a double socket that can sarry 26 amps is not going to be common item. ( other than the washing machine + drier situation ) .... So maybe the regulations were written with that in mind ( and assuming two single sockets would installed for the washing machine + drier situation.)

That all seems perfectly reasonable (and we've discussed it before) but I'm not sure that it is a 'safe' way of establishing a standard. Whilst, as you say, it's very unlikley that many people would have, let alone use simultaneously from the same double socket, two 13A loads, it is not totally impossible - and I think you would probably struggle to find any Joe Public who had even dreamed of the possibility that a double socket could not safely serve 2 x 13A loads. Given your usual attitude to 'the extremely unlikely' (but not impossible), I would have expected you to be saying that the only 'safe' option would be for the Standard to require that they could safely carry 26A.

Having said all that, there may be a wider problem, particularly if the sockets are nont wired satisfactorily and/or the sockets/plugs deteriorate with time, since we do hear reports of over-heating with dryer+WM combinations. Modern dryers rarely use anything like 3kW, and even that ccyles on and off to some extent, and, even if they can use 3kW at times, a WM will only do so for brief periods. I would therefore suspect that the average total load of a dryer+WM over a reasonable period of time is usually well under 26A, and very probably appreciably less that 20A (despite the thermal damage that some people experience).

Kind Regards, John

 

[JohnD]

Modern dryers rarely use anything like 3kW, and even that ccyles on and off to some extent

Mine does. Are you thinking of heat-pump models?

a WM will only do so for brief periods.

mine heats for 15 mins on a cotton wash

So it would be quite possible to be drawing about 6kW for 15 minutes continually if both machines were running together.

Obviously my futility room has an ample supply of single sockets.

 

[JohnW2]

Mine does. Are you thinking of heat-pump models?

No, just an 'ordinary' one. Mine is 'rated' at 2.6kW but, in practice, appears to draw 2.4-2.5 kW.

mine heats for 15 mins on a cotton wash. So it would be quite possible to be drawing about 6kW for 15 minutes continually if both machines were running together.

Indeed - if (as you say), your dryers uses 3kW continuously. However, even that would (if that 15 min were the only WM heating) only represent an average of around 4.5kW (19-20A) over 30 mins, or around 3.75kW (~60A) over an hour (and don't forget that the BS1363 temperature rise test relates to a minimum of 4 hours continuous loading).

Kind Regards, John

 

[harveycatt]

I have just come off the phone to MK and their tech guy says anything up to 20 amps is fine when using a double socket.

 

[JohnW2]

I have just come off the phone to MK and their tech guy says anything up to 20 amps is fine when using a double socket.

I don't think anyone would disagree with that, given that the relevant Standard (BS1363-2) requires that it can tolerate 20A (at least, when that 20A is made up of 14A+6A) for at least 4 hours.

If you ever speak to them again, you could try to get them to tell you what is meant by "13A per socket outlet" (I couldn't get a straight answer out of them!) - since that is what they claim is the rating of their double sockets!

In any event, as has been said, if you want to be cautious, then you couldn't do any better than having two single sockets.

Kind Regards, John

 

[EFLImpudence]

Yes, of course it is.

Did he say why not 26A and what would happen if you did that?

 

[AndyPRK]

Looking at JohnW video, where he opens a modern MK socket,
I can't see any reason why it couldn't do 13A both sides.
There is about 10mm of metal which supplies both sockets, and it looks very wide

from 9:45

You never miss an opportunity to talk about shutters, do you John.


I can't say the same about the Tenby socket, where the neutral bar to the terminal is the same width as the rest of the socket.

 

[JohnW2]

... I can't see any reason why it couldn't do 13A both sides. ... There is about 10mm of metal which supplies both sockets, and it looks very wide

I don't think it's what is 'supplying the sockets which is the potential issue, since one imagines that most of the heat produced will be at the interface between the plug's pins and the 'receptacles' in the socket.

In terms of heat dissipated in the material of the sockets' body and, more relevant, the faceplate, (rather than conducted along connected cables), with 2 x 13A that will ('if all other things are equal'!) be twice the amount of heat as with 1 x 13A, yet the faceplate of the double socket is less than double the area and mass of that of a single socket - so one would expect a greater temperature rise in a double socket with 2 x 13A than with 1 x 13A in a single socket.

Kind Regards, John

 

[Risteard]

It's not nonsense from me in terms of what the MK Technical Data Sheets have said for very many years (at least 10 years - see below). As I have said, although what they have written is potentially ambiguous (and MK Tech Support can't clarify that issue!), there are only two possible interpretations - that the total 'rating' of a double socket is either 26A or 13A (and, as EFLI and I have both said, the latter seems pretty unlikely).

As for your link, we have often discussed the quote from MK which appears within that thread. As you have shown, it appeared in the IET forum 10 years ago and, even then, no-one knew where the MK quote had come from - and people were saying (as you can see if you read that thread) that, even then, the stated 'rating' of MK sockets was, at that time, exactly as it is today (i.e. 13A "per socket outlet"), even though that material (presumably from MK at some point in history) said ...



Kind Regards, John

MK state:

"All MK socket-outlets are manufactured to comply with BS1363 part 2: 1995 and are rated at 13A per unit. Double socket-outlets have been manufactured and tested to exceed this rating by margin that allows electrical safety and reduces the risk of heat and mechanical damage to components due to overloading. It should be noted that BS1363 part 2: 1995 does not allow double sockets to operate at twice the permissible maximum loading and it should be remembered that double socket-outlets are not manufactured to be able to withstand a 26A load for sustained periods of time.

"Research by ourselves and third party organisations has shown that all MK double sockets can safely withstand a continuous load of 19.5A for an indefinite period. Increasing the load slightly will begin to cause heat and mechanical stresses on the components in a relatively short period. Testing showed that a load of 22.3A was sufficient to cause heat stress that would cause a browning of the faceplates and sufficient heat to cause insulation damage to cable cores. A load of 24A for 43 hours was sufficient to cause significant heat damage to the material in which the socket-outlet was situated and within 75 hours sufficient to cause significant damage that would lead to the very real potential of fire.

"MK recommend that users of their sockets consult professional design Engineers when designing installations to avoid the possibility of heat and mechanical stress to components and installations caused by overloading of MK socket-outlets."

 

[JohnW2]

MK state: <another copy of what I posted>

Did you actually read my post to which you're replying and, indeed, the thread from which that came?

You've just posted exactly the same material as I did in the post to which you are replying. As I said, that material is at least 10 years old, no-one knows exactly where it came from, and that, even back then, MK data sheets said (as they do now) that the capacity of a double socket was "13A per socket outlet" (which, as I said, means either 26A total or 13A total - which do you think is the more likely?).

Kind Regards, John

 

[AndyPRK]

I note when mk sell filtered sockets they engraved on the front TOTAL LOAD 13A
CORRECTED

IT’s 13A between the 2 sockets.

 

[JohnW2]

I note when mk sell filtered sockets they engraved on the front 13A maximum. Is 13A between the 2 sockets.

You tell me - it's really the same question as with MK non-filtered double sockets which don't have that engraved on them!

13A max across two 'socket outlets' would be rather odd. Would it mean that it was OK to have 13A going through one and nothing through the other, or would it mean, say, 6.5A maximum for each?

Kind Regards, John