How to change a fuse on a plug socket

[JohnW2]

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Hmmm. Needless to say, I know that I can do that - but this is nothing to do with me, and I cannot insert a link into someone else's post. I was merely pointing out that ban-all-sheds had apparently posted in the wrong thread - and only he or you can do anything about that, other than (as I did) bringing people's attention to the error.

Kind Regards, John

 

[winston1]

Well I would say it is a historic thing, before we joined the EU we did use the fuse in the plug to protect the appliance, however to harmonise it was realised that if UK stuff was taken into Europe it could be a problem when the plug is changed. So the rules changed, not sure what date, but my son is 40 now, so it was at least 25 years ago when they went to school. At that time what was written on the plate was used to work out fuse sizes.

Today there are two things which control the fuse size, one the cable, and two the connector, it does not matter what size cable is used with a fig of 8 lead set, that socket is rated 2.5 amp so the fuse will be no bigger than 3 amp. We have a range of connectors rated 0.2 (shaver) 2.5, 6, 10 and 16 amp, ups there we go again with 6 amp and we only have 5 or 7 amp fuses.

So we need 2.5, 6, 10 and 13 amp fuses to protect cable and connector, but that's not what we can buy.

Right from the start of the fused plug it was stated that the fuse was to protect the cable, not the appliance.

You may think that 3 amp fuses should be used on fig 8 leads but the fact of the matter is that in Europe such leads are only protected by a 16 amp MCB without problems.

 

[JohnW2]

You may think that 3 amp fuses should be used on fig 8 leads but the fact of the matter is that in Europe such leads are only protected by a 16 amp MCB without problems.

I don't doubt that there are few, if any, problems. However, I'm not sure that one should advocate putting anything up to 16A (depending upon the nature of the load) through a connector 'rated' at 2.5A, should one?

Kind Regards, John

 

[EFLImpudence]

No but the fact that an accessory, socket or plug is only rated at 2.5 amps means it should not be used for an appliance greater than that.

The fuse is still to protect the cable.

 

[ericmark]

The Europlug is a flat, two-pole, round-pin domestic AC power plug, rated for voltages up to 250 V and currents up to 2.5 A. It is a compromise design intended to connect low-power Class II appliances safely to the many different forms of round-pin domestic power socket used across Europe.

So the plug is 2.5 A the cable is likely 2.5 A and the fig of 8 socket is 2.5 A if some one plugs it in to a 16A socket then more fool them. When I watch car races it does not mean I drive that way, and in the same way if some one in Europe wants to break the rules that's their look out, it does not mean I should copy them.

 

[JohnW2]

No but the fact that an accessory, socket or plug is only rated at 2.5 amps means it should not be used for an appliance greater than that.

Indeed, but if the cable/plug are supplied as a standalone item (not together with 'thye appliance'), I would have thought that it makes sense to do something to try to limit the current that could go through the 2.5A-rated plug, and having (when/where possible) a low-rated OPD somewhere in the path is one way of moving in that direction (even if one can't do that outside of the UK!).

Kind Regards, John

 

[EFLImpudence]

Indeed, but if the cable/plug are supplied as a standalone item (not together with 'the appliance'), I would have thought that it makes sense to do something to try to limit the current that could go through the 2.5A-rated plug,and having (when/where possible) a low-rated OPD somewhere in the path is one way of moving in that direction (even if one can't do that outside of the UK!).

It may well be wise, if and when necessary. I would include that in 'protecting the cable'.

However, are there any ≤ 2.5A appliances which can cause an overload. Indeed, how many will be anywhere near 600W?

This is the same argument for 'lighting' circuits being protected by 6A MCBs (even though using 16A cable).
That is - the switches are only rated at 6A but how many switches have anything approaching 6A going through them.

I know your "might as well argument" but that does not answer the questions.

 

[JohnW2]

It may well be wise, if and when necessary. I would include that in 'protecting the cable'.

Well, "protecting the cable and connector". Indeed, if it is a moulded connector, one could well argue that it was effectrively part of 'the cable'.

However, are there any ≤ 2.5A appliances which can cause an overload. Indeed, how many will be anywhere near 600W?

Very few, if any, I imagine. However, I was talking about the possibility of a 'sold alone' cable+plug being plugged into something which drew >2.5A.

This is the same argument for 'lighting' circuits being protected by 6A MCBs (even though using 16A cable). That is - the switches are only rated at 6A but how many switches have anything approaching 6A going through them.

Indeed. As often discussed, I think that the 6A MCB arose only as a perpetuation of the 5A fuse, neither of which probably had a particularly logical electric basis.

I know your "might as well argument" but that does not answer the questions.

I'm not particularly trying to answer questions but, yes, I do subscribe to the view that, in any situation, one "might as well" use the smallest OPD which will allow the circuit/appliance to function satisfactorily - not the least because (given the absence of downsides) it is conceivable that a 'benefit' might very occasionally result.

Kind Regards, John

 

[EFLImpudence]

I think I may have got confused between Eric's post advocating a 3A fuse for the plug/cable and Winston's saying it it not for protecting the appliance.

Very few, if any, I imagine. However, I was talking about the possibility of a 'sold alone' cable+plug being plugged into something which drew >2.5A.

True, but that same person may do all sorts of wrong things.

 

[JohnW2]

I think I may have got confused between Eric's post advocating a 3A fuse for the plug/cable and Winston's saying it it not for protecting the appliance.

Yes, possibly. There is a more 'grey' middle-ground in terms of 'protecting the connector'.

Whilst it can be (and often is!) argued that an external OPD should not be required to protect 'an appliance/equipment', since that should have adequate internal protection, the corresponding argument does not really apply to connectors, since (with the possible exception of BS1363 plugs, depending upon how one looks at it), they generally do not have (and are not expected to have) any 'internal protection'.

Kind Regards, John

 

[ericmark]

With lighting I would say more down to ceiling rose which is used as a junction box and only rated 5 amp.

As to connectors and cable the C13 to C16A have been a problem for those doing inspection and testing of in service electrical equipment (PAT testing for short) as the same plugs can be used from a computer to a kettle and although all are rated 10 amp, the cable is often too thin to supply 10 amp and it needs very careful inspection to see what cable is used.

I have not had a 10A fuse blow even when used with a 3 kW kettle, however some items do draw the 3 kW for longer than the time taken to boil a kettle. I was told there are two preferred sizes, 3 amp and 13 amp, I would buy packs of 3 amp, but always seemed to have an excess of 13 amp. But should one really fit a 13A fuse to a lead set only rated 10A even if the kettle it supplies is rated 3 kW? Is this

so you can boil two kettles together?

 

[sparkwright]

I would say calculating the minimum fuse size based on the wattage of these appliance would be a reasonably fool proof method for someone to decide which fuse to fit - because the average DIYer isn't going know the CABLE size.

 

[EFLImpudence]

With lighting I would say more down to ceiling rose which is used as a junction box and only rated 5 amp.

That could be true, but the connector blocks look very similar to these which are rated for 16A.

 

[Astra99]

When I was writing the procedures and risk assessments for Portable Appliance Testing, one of the points was the connector on a "loose" lead, and the size of the conductors in that lead. C5 and C7 (cloverleaf and figure of eight) had fuses of 3A specified and C13 with 0.75mm² cable 5A, C13/C15 with 1.0mm² 10A.

I would go on to say that the cable size is embossed on the outer sheath.

 

[JohnW2]

With lighting I would say more down to ceiling rose which is used as a junction box and only rated 5 amp.

I would agree if I found it able to take that 5A 'rating' seriously. I strongly suspect that if one could get the required conductors into them, those 'lumps of brass' could happily carry 5, if not even 10 or more times that current!

I have not had a 10A fuse blow even when used with a 3 kW kettle, however some items do draw the 3 kW for longer than the time taken to boil a kettle....

As we have observed before, it seems that one needs a current of at least 21A-22A to ever blow a 13A BS1362 fuse (even if that current persists 'for ever').

Kind Regards, John