13 Amp fuse for a 35 watt appliance .........

[ericgibbs]

Indeed - just looked that up myself.

Looks very much like an email to the manufacturers might be in order to see what they have to say.

I would be interested in their response.

 

[picbits]

I'll dig out the instructions over the weekend and fire an email off to them on Monday.

Will let you know their response.

 

[Top Cap]

Case proved I think for the fuse protecting the cable, if it is only rated 6 Amps then a 5A fuse should be fitted. In fact you might even get away with fitting a 3A one. Here's food for thought but albeit a bit OT, many manufacturers recommend a 13A fuse for appliances using the 3 pin IEC connector. The cable fitted is usually substantial yet the connector itself is only rated at 10 Amps. It would be an interesting court case if an IEC connector manufacturer was blamed for a fire from an appliance fused at 13A. Of course the scenario is unlikely to happen but what about today's risk assessment and hazard analysis we design engineers have to suffer all the time. LOL!
Les
P.S. Is there an Earth wire on this appliance to make it a class 1 product?

 

[ericgibbs]

Case proved I think for the fuse protecting the cable, if it is only rated 6 Amps then a 5A fuse should be fitted. In fact you might even get away with fitting a 3A one. Here's food for thought but albeit a bit OT, many manufacturers recommend a 13A fuse for appliances using the 3 pin IEC connector. The cable fitted is usually substantial yet the connector itself is only rated at 10 Amps. It would be an interesting court case if an IEC connector manufacturer was blamed for a fire from an appliance fused at 13A. Of course the scenario is unlikely to happen but what about today's risk assessment and hazard analysis we design engineers have to suffer all the time. LOL!
Les

I cannot see how you get the 'case proved' from this unconfirmed query.

Remember less qualified people will be reading these posts, I wouldn't like them to take for granted,
the bigger the cable the bigger fuse concept.

 

[picbits]

My partner has a pair of xxxxx hair straighteners. I have a query on the fuse rating for this product. It says on the plug that it is fitted with a 13amp fuse (which indeed it has) and also states in the manual that it is to be fitted with a 13amp fuse.

The rating plate on the product says the product is rated at 35watts, 220-240 volts at 50Hz.

I have tested these and see an initial peak of 600 watts settling down to around 65 watts after one minute of heating up.

The cable is marked 2 x 0.75 which appears to be 0.75mm2 mains cable which is rated at 6amps maximum.

Could you verify that using a 13 amp fuse on a 35 watt product with mains cable which is only rated at 6 amps is safe to use please ? We are currently discussing this on an electronics forum and the general feeling is that a 5 amp fuse should be fitted.

Many thanks
Dom

Just sent this email off to them - will be interesting to see their reply.

 

[Top Cap]

Hi Eric, I understand your concerns but that is how it is nowadays, probably due to the almost wide spread use of the IEC connector. If you designed some equipment to run on 5A say, you MUST employ some kind of protective device inside the equipment as otherwise someone could connect another IEC cable fitted with a higher fuse i.e.13A. I work with some of the most knowledgeable persons in product safety and they all stipulate that the fuse in the plug is only there to protect the cable feeding the appliance. Like a lot of modern rules, they do appear to be rather stupid at times but nonetheless they are there so the best thing to do is, if no appliance protection is fitted, is to fuse at the rating stated on the plate of the appliance. I do that myself but it does not alter the foregoing about appliance cable size and fuse. In that respect I am just the messenger boy, please hold your fire!

 

[Nigel Goodwin]

Hi Eric, I understand your concerns but that is how it is nowadays, probably due to the almost wide spread use of the IEC connector. If you designed some equipment to run on 5A say, you MUST employ some kind of protective device inside the equipment as otherwise someone could connect another IEC cable fitted with a higher fuse i.e.13A. I work with some of the most knowledgeable persons in product safety and they all stipulate that the fuse in the plug is only there to protect the cable feeding the appliance. Like a lot of modern rules, they do appear to be rather stupid at times but nonetheless they are there so the best thing to do is, if no appliance protection is fitted, is to fuse at the rating stated on the plate of the appliance. I do that myself but it does not alter the foregoing about appliance cable size and fuse. In that respect I am just the messenger boy, please hold your fire!

You are working on an entirely false premise, that all appliances have plugin mains leads, this is the exception rather than the norm - an item with a fixed mains lead has no need to have an internal mains fuse, though many of course do.

Also, IEC connectors come in two basic types, low current and high current, and you can't fit a low curent lead in a high current socket.

 

[Diver300]

I've seen how much damage a short causes when it is only protected by a 13A fuse.

I often fit lower fuses than the appliances come with. My most usual size is 1A.

The appliance rating is usually a good indication of the fuse needed. The only time that you need a larger fuse is when there is a large motor in the appliance. One fridge rated at 200 W or so would blow a 3A fuse eventually.

The worst fusing I came across was a slow cooker rated at 250 W that came with a 13A fuse. It is only resistive so there was no surge at all, so a 2A fuse is fine.

I agree that IEC320 C13 leads shouldn't have a fuse above 10A. Also the IEC320 C7, figure of 8 connectors are rated at 2.5 A so the fuse shouldn't be higher than that, although I don't think that a 3 A fuse is pushing it too far.

 

[Hero999]

13A for 0.75mm² cable, that sounds dodgy.

What is the cable insulation made from? If it's PVC then no way but if it's high temperature 150°C silicon rubber then it might be alright.

 

[picbits]

Cable insulation is unknown, its feels like pretty decent quality cable though and it wouldn't suprise me if it was high temperature.

Will post up their reply (if I get one).

 

[picbits]

Here is the reply from the manufacturer :

Thank you for your email.



I passed your email on to our test Engineer, please see below for his reply:-



Under normal use there is no overload of the cable.



A 3A fuse is not fitted because of the possibility of the switch-on current may cause it to blow prematurely.



There are two preferred values of fuse 3A and 13A in the fuse standard. Therefore the alternative 13A fuse is fitted. The standard for plugs refers to the fitting of a 13A fuse for 0.75mm² cable during the testing of plugs.



There are two possible failure modes for the product, either it becomes open circuit which is not a problem for the fuse or cable, or, there is a short circuit in which case the fuse blows very quickly and the cable is protected.



Hope this is information is sufficient and helpful.





Yours Sincerely

 

[crutschow]

Good engineering practice is to have a fuse no larger than the appliance requires. If something shorts, you don't want more current flowing than necessary. And if you get a high resistance short you could be dissipating a large amount of power without blowing the fuse. 13A (3100W) for a 35W appliance is total overkill. If there's a concern about surge current, use a slo-blo fuse.

 

[ericgibbs]

Good engineering practice is to have a fuse no larger than the appliance requires. If something shorts, you don't want more current flowing than necessary. And if you get a high resistance short you could be dissipating a large amount of power without blowing the fuse. 13A (3,100W) for a 35W appliance is total overkill. If there's a concern about surge current, use a slo-blo fuse.

hi Carl,
I agree.

People keep talking about short circuits which is not always the case.

Like you, I rate fuses to be the lowest possible value that avoids blowing at switch ON, slow blow usually gets the job done, this would apply to picasm's type of hand held appliance.

 

[picbits]

Who's Picasm ?

 

[ericgibbs]

Who's Picasm ?

Woops! Having a Senior moment, Sorry picbits

 

[Hero999]

The IEE regulations would advise against using a 13A fruse for 0.75mm² cable.

I can see why he didn't use a 3A fuse but I don't understand why he didn't use a 5A fuse, perhaps the surge current would still be too high.

 

[ericgibbs]

The IEE regulations would advise against using a 13A fruse for 0.75mm² cable.

I can see why he didn't use a 3A fuse but I don't understand why he didn't use a 5A fuse, perhaps the surge current would still be too high.

There are also 7A and 10A fuses available for domestic UK mains plugs.

 

[Nigel Goodwin]

There are also 7A and 10A fuses available for domestic UK mains plugs.

And 5A for that matter, but the two most common values are 3A and 13A.

 

[Hero999]

I've not seen very many 7A and 10A fuses, 5A is the most common value after 3A and 13A.

 

[Top Cap]

I was rather surprised to find that though .75mm2 is rated at 6A, the silicon insulated version is rated a full 13A. Possibly that is the type of cable being used for the device, especially as heat is involved and how the manufacturers get away with fitting a13A fuse.