Dishwasher and Plinth Heater in same Double Socket ?

[JohnW2]

I thought you corrected me when I said that once, by quoting a regulation where it actually says only one accessory.

To the best of my knowledge, there are no relevant regulations. Beyond saying "with or without spurs", the very brief reg which permits ring finals says nothing at all about spurs, or what may be connected to them - and, again to the best of my knowledge, nor does any other regulation.

Kind Regards, John

 

[JohnW2]

I can't remember what the outcome of a long previous discussion about plugging two 13 amp appliances into one double socket was. Someone in the past said an MK double socket was rated a 26 amp, rather than 13 amp - but how true that is I don't know.

No-one seems to be sure where it came from, but the following, attributed to "an MK article" gets periodically posted here and elsewhere:

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.

You might also be interested to read what I wrote here about 5 years ago:

Following the recent endless discussion about the 'current rating' of double sockets, I have now had the opportunity to discuss this with a technical support engineer at MK/Honeywell. I am therefore now fairly clear as to their position, even if it seems a rather unsatisfactory situation:

• 1. The statement in their technical literature for Logic Plus sockets which reads "Current rating: 13A per socket (except 3 gang, which is 13A total)" is not only confusing and ambiguous, but simply wrong - and his 'explanation' was that this literature was created by the marketing department, over whom the engineers have limited control! MK (MK's engineers) do not intend to imply EITHER that the double socket can only supply 13A total, OR that it can supply 26A total.
  
  2. Similarly, he did not really know why all double sockets have "13A" embossed on the back, again because this is not the intended 'rating' of either half or all of the double socket.
  
  3. MK do not claim, recommend or suggest that their BS1363 sockets have any greater current carrying capacity than anyone else's. In common with all manufacturers, they merely seek to comply with BS1363, in particular the 20A temperature rise test. MK's (engineers') only view on the 'rating' of their (and everyone else's) double sockets is therefore based on the BS1363 temp-rise-test figure of 20A - although he did add that he thought most designers would try to avoid a situation in which one double socket was likley to be loaded with as much as 20A (although it's not all that clear as to how that would be achieved - unless on installed only single sockets!).

So, that really answers the question I posed at the very start of that other infamous thread. The chap I talked to said that he would pass on my 'compliant' about the potentially misleading literature to their marketing department, but I don't think I'll be holding my breath whilst waiting for any changes! There doesn't seem anything more to discuss.

Kind Regards, John

 

[stillp]

The erroneous statement that "It should be noted that BS1363 part 2: 1995 does not allow double sockets to operate at twice the permissible maximum loading" casts doubt on the veracity of any of their other statements.
Like all standards, BS1363 specifies minimum requirements. It does not prohibit manufacturers from exceeding those requirements.

 

[JohnW2]

The erroneous statement that "It should be noted that BS1363 part 2: 1995 does not allow double sockets to operate at twice the permissible maximum loading" casts doubt on the veracity of any of their other statements.

Indeed - it should really say "require", rather than "allow".

I suppose one of the problems for manufacturers is that if they did want to manufacture a double socket that would pass a BS1363-like temperature rise test at 26A (i.e. identical test to the BS1363 onne, but conducted at 26A), buyers would have to 'take their word for it', because they could not cite compliance with any Standard which required a 26A test. In other words, it would therefore only able to bear a BS1363 marking, just like those products which could 'only just' pass the BS1363 (20A) test.

Kind Regards John

 

[EFLImpudence]

The erroneous statement that "It should be noted that BS1363 part 2: 1995 does not allow double sockets to operate at twice the permissible maximum loading" casts doubt on the veracity of any of their other statements.

I would be so bold as to say - Nothing should be allowed to operate at twice the permissible maximum loading.

 

[stillp]

Well, that would be a circular argument, since if it was allowed it would be permissible!

 

[EFLImpudence]

Pedant.