Why don't lamps come with a 1 amp fuse in the plugs?

[eveares]

When ever you buy a plug in light/lamp, they always come with a 3 amp fuse in the plug?

Now as most of these lamps will be drawing under 230 watts, would it not be more safer to have a 1 amp fuse in the plug instead?

And while the cable and lamp holders of most lamps is rated at least 3 amps and likely the reason for the 3 amp fuse in the plug, is it not best practice to use the lowest fuse ratting suitable?

 

[JohnW2]

When ever you buy a plug in light/lamp, they always come with a 3 amp fuse in the plug? ... Now as most of these lamps will be drawing under 230 watts, would it not be more safer to have a 1 amp fuse in the plug instead?

I would personally say so - we've often discussed this before. I do personally use a lot of 1A fuses, but suspect I'm the exception, rather than the rule!

And while the cable and lamp holders of most lamps is rated at least 3 amps and likely the reason for the 3 amp fuse in the plug, is it not best practice to use the lowest fuse ratting suitable?

Again, I would personally say so. The nearest to an 'explanation' (for the 3A fuses) I've heard is that 1A is 'not a preferred size' - go figure!

Kind Regards, John

 

[ricicle]

The fuses in the plug are generally there to protect the cable rather than the appliance or fitting and can be sized accordingly.
Also 3 and 13A fuses were the only rating to be officially recognised by the standard hence them having their own colours, while all others are black and white.

 

[Taylortwocities]

Similarly, when one buys a BS1363 plug (or an FCU) they always come with a 13A fuse fitted. This can cause problems for the unwary.
Wouldn't it be safer if they were supplied with the minimum sized fuse (3A) ?

 

[JohnW2]

The fuses in the plug are generally there to protect the cable rather than the appliance or fitting and can be sized accordingly.

Indeed - but, given that the appliances/fitting are rarely provided with any/adequate internal fusing, it does seem to make sense to use a fuse which affords at least some protection to whatever is within the item. After all, we could usually use, say, 16A OPDs to protect 1.5mm² lighting circuits if we were concerned only about cable protection and not about what was 'on the end of the cables'.

Also 3 and 13A fuses were the only rating to be officially recognised by the standard hence them having their own colours, while all others are black and white.

Indeed - as I said, 1A is not a 'preferred' (or, as you say, even 'officially recognised') size' - but that certainly doesn't stop me make fairly widespread use of them

Kind Regards, John

 

[EFLImpudence]

Wouldn't it be safer if they were supplied with the minimum sized fuse (3A) ?

It would be 'safer' but then people would be taking them back complaining they don't work.

When would a 3A fuse actually be required?
I.e. which appliances for which you would fit a 3A fuse would actually overload the cable? - apart from extractor fans.

 

[JohnW2]

Similarly, when one buys a BS1363 plug (or an FCU) they always come with a 13A fuse fitted. This can cause problems for the unwary. Wouldn't it be safer if they were supplied with the minimum sized fuse (3A) ?

I think it would - or, at least (to avoid inconvenience to those who discovered that they had to go back to the shop to buy a 13A fuse, when required!), supply them with no fuse fitted but with 3A and 13A (and perhaps 1A ) fuses sold ('bundled') with them.

Kind Regards, John

 

[rsgaz]

Wouldn't the inrush current eventually blow a 1 Amp fuse? I know they can handle more than 1 Amp for a short time, but every single time you used the lamp would eventually take it's toll I would have thought?

First Google image that came up shows approx 3.5 Amps for a 100w lamp.

Gaz

 

[diyer56]

B&Q supply 13A plugs with various size fuses included:

13A with 13A fuse:
http://www.diy.com/departments/bq-13a-3-pin-plug/208489_BQ.prd

13A with 5A fuse:
http://www.diy.com/departments/bq-13a-3-pin-plug/170979_BQ.prd

13A with 3A fuse:
http://www.diy.com/departments/bq-13a-3-pin-plug/170982_BQ.prd

you pay 19p for the privilege

 

[JohnW2]

Wouldn't the inrush current eventually blow a 1 Amp fuse? I know they can handle more than 1 Amp for a short time, but every single time you used the lamp would eventually take it's toll I would have thought? ... First Google image that came up shows approx 3.5 Amps for a 100w lamp.

Yes, but it's only above 1A for around 10 msec, and only above 2A for 2-3 msec. I suppose that, in theory, this would 'take some toll' but I doubt that, in practice, it would end up with the fuse blowing - not for many years, at least! In any event, in this day and age it's more likely to be a <20W CFL or LED than a 100W incandescent!

Kind Regards, John

 

[eveares]

Also 3 and 13A fuses were the only rating to be officially recognised by the standard

Have 5 amp fuses never been officially recognised either? I grew up with 3, 5 and 13 amp fuses being the ones commonly sold.

It would be 'safer' but then people would be taking them back complaining they don't work.

Then supply plugs without fuses fitted then and make it very clear that the user has to by a fuse of an appropriate rating.

Can anyone also provide the time/current characteristics for a 1 amp BS1362 plug top fuse. Are these 1,2,5,7 and 10 amp fuses even truly to BS1362?

 

[JohnW2]

Have 5 amp fuses never been officially recognised either? I grew up with 3, 5 and 13 amp fuses being the ones commonly sold.

According to the Wikipedia:

The original BS 1363:1947 specified fuse ratings of 3 A, 7 A and 13 A.[48] The current version of the fuse standard, BS 1362:1973, allows any fuse rating up to 13 A, with 3 A (coloured red) and 13 A (coloured brown) as the preferred (but not mandated) values when used in a plug. All other ratings are to be coloured black.

Can anyone also provide the time/current characteristics for a 1 amp BS1362 plug top fuse. Are these 1,2,5,7 and 10 amp fuses even truly to BS1362?

See above. I can't help with time'current characteristics other than for 3A and 13A.

Kind Regards, John

 

[AndyPRK]

What happens when a lamp or CFL fails> Would that not stress a 1A ?


Plugs with sensible sized fuses have been available for a number of years.


Also remember that appliances come fitted with plugs these days so there isn't must call for the public to be purchasing plugs and fitting the wrong fuse

 

[JohnW2]

What happens when a lamp or CFL fails> Would that not stress a 1A ?

If it were something approaching a (transient) 'dead short', it would probably 'stress' even a 13A fuse. Furthermore, if a current considerably in excess of 1A were to flow for a significant time as the result of the death of a lamp, one might hope that the fuse would not only get 'stressed' but would actually operate - after all, that's what fuses are for!

Plugs with sensible sized fuses have been available for a number of years.

They have, but 13A very much remains the 'default', and probably all that is available from many sources.

Also remember that appliances come fitted with plugs these days so there isn't must call for the public to be purchasing plugs and fitting the wrong fuse

That's true, and it means that it's now much less of an issue that it was a few decades ago - but I bet there are still an awful lot of plugs being sold, for whatever reason!

Kind Regards, John

 

[AndyPRK]

Furthermore, if a current considerably in excess of 1A were to flow for a significant time as the result of the death of a lamp, one might hope that the fuse would not only get 'stressed' but would actually operate - after all, that's what fuses are for!

But you wouldn't want to replace a fuse every time a lamp failed.

I guess in relativity that doesn't happen as you would know about it!


What would you speculate plugs are purchased for these days ?