Burnt Out 13-Amp Plug

[JohnW2]

I was in the EU three times today. It's a wonder I didn't get CE marked.

At least you didn't have to spend all day waiting in a queue at the 'border'!

 

[SUNRAY]

One of my regular calls is to a factory which uses infra red heaters (3kw) plugged in to 13 amp sockets, pays for my wine

Funny that... IR heaters and 13A plugs burning out.
In my experience IR heaters are not very effective. Oh I've sussed it, it's obvious now... the heat comes out of the plug

I also had regular visits to a factory for the same problem, eventually I replaced a 13A plug and socket with a 15A and within a year all had been replaced, never had to see to them again. I was going to use 16A, even had the bits in the car but they used many of them around the buildings and they didn't didn't want the heaters unplugged and sockets used for something else.

 

[winston1]

I seem to recall the Post Office (or maybe BT) downgraded 13a plugs to 8a on their premises.

It would appear the BS1363 plug/socket system is not fit for purpose. Time for a change perhaps!

 

[JohnW2]

It would appear the BS1363 plug/socket system is not fit for purpose. Time for a change perhaps!

I don't think there's a lot wrong with the "BS1363 plug/socket system" (the Standard), so that a lot of the issue is presumably that some of the products are not necessarily BS1363-compliant.

One could perhaps suggest that the "system" (Standard) could be 'made better' if the temperature-rise test had to be done at 26A, rather than at 20A, and certainly if a way could be found to introduce some test(s) which related to required performance during/after long-term service (although that would be difficult).

 

[DetlefSchmitz]

As someone above mentioned, there is probably no issue with brand new parts. However as time goes by, the plug pins and the socket spring contacts tarnish and their resistance goes up, out of spec. I have experienced this back when I was running loop resistance checks on my house, using a 13A plug connected to the tester. None of the readings was in spec, they were all over the place. The only way to get a good reading was to insert the plug about twenty times to remove the tarnish.

 

[JohnW2]

As someone above mentioned, there is probably no issue with brand new parts. However as time goes by, the plug pins and the socket spring contacts tarnish and their resistance goes up, out of spec. I have experienced this back when I was running loop resistance checks on my house, using a 13A plug connected to the tester. None of the readings was in spec, they were all over the place. The only way to get a good reading was to insert the plug about twenty times to remove the tarnish.

Indeed, and I think that 'someone' was me.

As I just wrote, to address that issue would mean that BS1363 would have to contain some requirements about behaviour during long-term in-service use - and I'm not sure how practical that would be.

Kind Regards, John

 

[DetlefSchmitz]

Mmm. Artificial aging techniques are available for testing. But I doubt anyone cares enough. On the other hand I have seen plugs with plated pins that may be more resistant to tarnish. Not sure how well that works on the socket side though.

 

[winston1]

I don't think there's a lot wrong with the "BS1363 plug/socket system" (the Standard), so that a lot of the issue is presumably that some of the products are not necessarily BS1363-compliant.

Sunray’s experience seems to suggest there is as the problem went away once he had changed to 15a plug/sockets.

I believe the problems are due to the fuse or it’s contacts heating up.

As I said perhaps it is time to change. Overseas systems without fuses in the plugs don’t seem to have over heating problems.

 

[JohnW2]

Mmm. Artificial aging techniques are available for testing.

They are, in many fields, and give a guide, but they are rarely able to very effectively reproduce actually in-service conditions.

But I doubt anyone cares enough.

That could be true.

On the other hand I have seen plugs with plated pins that may be more resistant to tarnish. Not sure how well that works on the socket side though.

That makes some sense. However, as winston has said (and as witness what resulted in this particular thread) it seems that the issue is quite often associated with the fuse, rather than the pins.

Kind Regards, John

 

[JohnW2]

Sunray’s experience seems to suggest there is as the problem went away once he had changed to 15a plug/sockets.

Yes but, as I implied, if the plugs/sockets had been truly BS1363-compliant, he may not have needed to change to 15A ones.

I believe the problems are due to the fuse or it’s contacts heating up.

That certainly often seems to be the case, but the requirements of the Standard should really address that.

As I said perhaps it is time to change. Overseas systems without fuses in the plugs don’t seem to have over heating problems.

The reality is that the repercussions of the change that you think 'it may be time for' would render the change almost unthinkable in the UK, as it is - unless you would be happy to see unfused plugs on 32A circuits (of which there must currently be countless millions in the UK).

Kind Regards, John

 

[mwahlgreen]

Very easy:
When using equipment for continuous loads like a electric heater in a cold room for more than a couple of hours. One MOST derate any wire or extension cords by 20%.
The same for a charging an EV.

It is actually in the standards: IEC 61439-1:2020 Appendix L4.2
https://webstore.iec.ch/publication/32338

It states that for continuous loads all internal wiring, panels and subpanels should be rated to only 80% of their rated values. This also applies to extensions cords, even as the standard directly does not cover these.

Before the update of the standard in 2020, it also stated something about deration or the deration was described somewhere else . However I have no access to older version of the standard.
As an EV electrical engineer I very qualified to make my statement.

Before HD 60264 was implemented in DK. The rule was to build for 75% load and never 100%.
Today any electrician (in EU) may make installation based on what load the customer wants for one outlet today...
In 5 years the customer need to change the socket or the wiring because the customer no wants to run a heater of that socket made for a lamp.

 

[JohnW2]

Very easy: When using equipment for continuous loads like a electric heater in a cold room for more than a couple of hours. One MOST derate any wire or extension cords by 20%. ... The same for a charging an EV. It is actually in the standards: IEC 61439-1:2020 Appendix L4.2

You seem to be implying that the 'ratings' (of cables, connectors and accessories etc.) we work with are not intended to relate to continuous usage, and I'm not sure that is necessarily the case.

In any event, if one decides that continuous use requires a 20% 'de-rating', then that can only really be applied to fixed wiring. This discussion relates to plugs/sockets (and 'extension cords') and, in relation to a sockets circuit, the designer has no control over what loads may be 'plugged in', and for how long. For such circuits, and things plugged into them, one could therefore only achieve what you suggest by always de-rating everything associated with such a circuit (cables, connectors accessories etc.) - which would essentially amount to re-defining the 'ratings'.

Kind Regards, John

 

[ericmark]

The 13A plug and socket was designed for heating homes at end of WW2 however some changes have likely derated the system.

1) reducing metal in pins to allow finger guards.
2) move to smaller metric cable.

But any fuse produces heat, and there needs to be a means to get rid of the heat, black plugs are better than white, and the larger the better to dissipate heat.

Flex, and plugs should be in free air.

 

[JohnW2]

The 13A plug and socket was designed for heating homes at end of WW2 however some changes have likely derated the system.
1) reducing metal in pins to allow finger guards.
2) move to smaller metric cable.

All true, but I very much doubt taht either of those factors, per se, have had any appreciable effect on heat production.

But any fuse produces heat, and there needs to be a means to get rid of the heat, black plugs are better than white, and the larger the better to dissipate heat.

Again, all theoretically true. However, I don't think that fuses usually get hot enough to cause any harm - when fuse-related overheating occurs in a BS1363 plug or FCU, it seems that it is almost always due to poor connections, not to the fuse per se.

Flex, and plugs should be in free air.

Maybe - but in the real world, they sometimes aren't, or can't, be - and the actual heat-producing items, particularly the fuses, obviously cannot themselves be 'exposed' in free air!

Kind Regards, John

 

[flameport]

61439-1 is a standard for low voltage switchgear.
'internal wiring' in this context is the wiring found within switchgear assemblies, NOT building wiring, extension cords or anything else.