Why don't cheap sockets handle over 5amp with photos

[martinxxxxxx]

I see a lot of burnt out sockets in student house kitchens, normally the kettle socket. I know we have had this before, but I come with pictures

Untitled

• martinxxxxxx
• 15 Sep 2012
• 1

Untitled

• martinxxxxxx
• 15 Sep 2012
• 1

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[securespark]

student house

That's why you see lots of burnt-out sockets.

To be fair, I only find burnt-out sockets after serious abuse or a loose connection in plug or socket.

I too find what you have in tenanted properties, particularly student lets, and 99% of them are down to the former, not the latter.

 

[matt1e]

student house

That's why you see lots of burnt-out sockets.

To be fair, I only find burnt-out sockets after serious abuse or a loose connection in plug or socket.

Agreed and it certainly looks as though the neutral is loose on the first pic
A good rule of thumb when tightening terminals - always use the biggest driver that fits
Ie a terminal driver that you use for light switch terminals is not the one that you should be using for socket terminals

 

[martinxxxxxx]

Well the terminals were tight, it is the first thing I check, on the first photo you can see the heat from the switch contact (which is in the live line in anycase) has burnt a hole through the plastic, no where near the neutral terminal and on the second picture you can see that it is the switch contact that is responsible for the burning. None of the fixed wiring is damage by heat, as it would be in the case of a loose terminal wire.
So why lay the blame on the poor students - they have only used appliances with a maximum of 13A appliance and fuse fitted. This socket should be rated and able to handle that. It is the skinflint landlord; fitting rubbish sockets; or the manufacturer of crappy sockets that is to blame (MB in this case).
Surely that is right? Students may use the kettle for all of their pot noodle meals, but the electricity supply should be able to deliver the power without burning out - right?

 

[JohnW2]

So why lay the blame on the poor students - they have only used appliances with a maximum of 13A appliance and fuse fitted. This socket should be rated and able to handle that. It is the skinflint landlord; fitting rubbish sockets; or the manufacturer of crappy sockets that is to blame (MB in this case). Surely that is right? Students may use the kettle for all of their pot noodle meals, but the electricity supply should be able to deliver the power without burning out - right?

Indeed. Certainly in this case, I don't see how one can possibly blame the users/students. I don't really think one can blame the landlord, either - even if (s)he has specified cheap accessories, they are still meant to be fit for purpose and compliant with BS 1363. Whether one can blame the manufacturer is also far from certain. The design, per se, is presumably 'fit for purpose' and passes all the tests required by BS 1363, so the questions are whether (a) their manufacturing/QC/QA processes are such that some units are leaving their factory which are not 'fit for purpose' OR (b) the requirements of BS 1363 (particularly in relation to long-term performance) are inadequate.

Given the very localised heat damage to just one pair of switch contacts, I would think that the most likely cause will have been some muck that got in between the contacts (the risk of which may well not be addressed by BS 1363 tests), causing a high resistance connection. If it were a manufacturing fault, then something resulting in inadequate pressure between the switch contacts would seem a likely suspect (or, of course, some surface 'fault' in the contact itself).

Kind Regards, John

 

[securespark]

All I'm saying is that when I come across this problem, it is mainly due to abuse, but then I visit an awful lot of tenanted and student properties.

 

[martinxxxxxx]

I have rarely changed over a MK or Crabtree or LeGrand one with this problem. And I agree more often than not it is the loose connections that cause problems. But in this case Not.
I wondered if we are back to the problem caused by the shrouding of the pins that is giving insufficient surface area

 

[JohnW2]

All I'm saying is that when I come across this problem, it is mainly due to abuse, but then I visit an awful lot of tenanted and student properties.

I understand that, but it's extremely difficult to see what sort of 'abuse' could result in the sort of problem we see here (overheating just of the switch contacts) - I suposse that 'playing with' the switch (repetedly switching it on/off, on load, for whatever reason!) is about the only thing which might just about do it!

Kind Regards, John

 

[JohnW2]

I wondered if we are back to the problem caused by the shrouding of the pins that is giving insufficient surface area

I don't think that the part of the pin which is shrouded would be part of the 'contact area', even if there were no shrouding - I think it's the size of the 'receptacle' within the socket (which does not even make contact with all of the metal part of the pin) which is the contact-area-limiting factor.

In any event, whilst reduced contact area (or repeated rough insertion/removal of plugs) might possibly result in overheating arising at the pin/socket interface, it could not possibly result in what we are seeing here - heat generation at the switch contacts.

Kind Regards, John

 

[martinxxxxxx]

I go into about dozens of student houses during the summer and as has been said above, this problem or similar happens a lot, so it is tempting to say the users are abusing the installation. Landlords are always asking me to state that, so they can make deductions from deposits. But I happen to think that as long as they don't swap the fuse in the their multi-adaptor plug for a nail; they are innocent of any blame. Do you think I am being unfair on the landlords

 

[EFLImpudence]

Not all adaptors have fuses.

So, it's easy to plug a kettle and toaster (and more) into one socket.

It's difficult to see what the landlord can do.
He does have you checking the installation.

 

[JohnW2]

I go into about dozens of student houses during the summer and as has been said above, this problem or similar happens a lot, so it is tempting to say the users are abusing the installation. Landlords are always asking me to state that, so they can make deductions from deposits. But I happen to think that as long as they don't swap the fuse in the their multi-adaptor plug for a nail; they are innocent of any blame. Do you think I am being unfair on the landlords

Not at all. As I said, I find it hard to see any rational way in which one could blame either the students or the landlords (and perhaps not even the manufacturers, if the accessories leaving their factory are, indeed, fully compliant with BS 1363) for this sort of problem.

As you say, replacing the fuse in a multiway adapter/extension with a nail, and then plugging in multiple high-load appliances would be about the only 'blameworthy' behaviour - and even that would not be very likely to result in the pattern of damage such as depicted in the OP.

Kind Regards, John

 

[JohnW2]

Not all adaptors have fuses. So, it's easy to plug a kettle and toaster (and more) into one socket.

True, but I would think it unlikely that even that would result in the pattern of damage we're being shown in this case - which looks like the result of poor contact between switch contacts, whether due to muck, inadequate pressure between contacts or surface abnormalities of the contacts.

Kind Regards, John

 

[JohnD]

these student-tenanted houses you keep going to, do you generally find that have been provided with good quality electrical accessories?

or are the landlords penny-pinching cheapskates?

 

[EFLImpudence]

Not all adaptors have fuses. So, it's easy to plug a kettle and toaster (and more) into one socket.

True, but I would think it unlikely that even that would result in the pattern of damage we're being shown in this case - which looks like the result of poor contact between switch contacts, whether due to muck, inadequate pressure between contacts or surface abnormalities of the contacts.

Why do you say that?

Surely the little 'blobs' in the switch which make contact are the weakest parts (smallest points of contact under proper usage) of the socket.


Edit - having reread your reply, you seem to be agreeing with me.
Why, then, is this damage inconsistent with my point?