Appliance fuses

[Ray Tay]

I see that washing machines come with a 13A fuse as standard when it may only draw around 4 amps. Common sense would say fit a 6A fuse. I intend to do this with my appliances, find out the amps drawn and put in a fuse to match.
Why are supplied fuses in appliance over rated? This surely must be less protection for the appliance and cables and flexes.
I noticed that flexes on some washing machines are not 2.5mm, so that cable is not protected fully. The flex could maybe draw too much current and heat up maybe causing a fire and the 13A fuse in the plug will not blow.

 

[bhm1712]

Fuses in plugs are not there to protect the appliance. They're there to protect the wire leading to the appliance. The same as the fuses or circuit breakers in the consumer unit.

The appliance will be internally protected by its own correctly rated fuse.

 

[bhm1712]

Depending on installation methods, 1.5mm cable is rated up to 15 amps and so a 13 amp fuse in a plug will only become a problem if the flex core size is less than 1.5mm (actually it's 1.25mm cable that is rated up to 13A but it's not often used nor found)

 

[bernardgreen]

when it may only draw around 4 amps.

It may draw a much higher current when the motor is working hard to accelerate the drum up to spin speed.

 

[endecotp]

I see that washing machines come with a 13A fuse as standard when it may only draw around 4 amps. Common sense would say fit a 6A fuse. I intend to do this with my appliances, find out the amps drawn and put in a fuse to match.

No, don't do that.
Do you honestly think you know more about this than the professional electrical engineers who designed the products?

 

[JohnD]

I see that washing machines come with a 13A fuse as standard when it may only draw around 4 amps.

Not if your washing machine is a typical UK one with a heating element to warm the water.

 

[Ray Tay]

endecotp, I am beginning to think I do. A 13A fuse when the appliances draws around 4A is way over rated. I was reading that they put 13A fuses in because the same appliance will sell in Europe where they have 16A radial circuits and no fuse in the plug. So it looks like a cover all for the makers.

bhm1712, washing machines do not have fuses in the appliance. So as you stated if the flex is 1.5mm the 13A fuse will protect it. But a lower fuse more in keeping with the current draw must be safer all around for the appliance and cables.

JohnD, what fuse rating have you seen? I have only ever seen 13A fuses in washing machines and dishwashers.

bernardgreen, The amps draw on motor start up must be in the maximum current rating on the badge?

 

[Ray Tay]

The average electric kettle draws 1800 watts, that is around 8A. A 10A fuse in the plug would do for that, yet 13A is in the plug.

 

[bhm1712]

endecotp, I am beginning to think I do.

bhm1712, washing machines do not have fuses in the appliance. So as you stated if the flex is 1.5mm the 13A fuse will protect it. But a lower fuse more in keeping with the current draw must be safer all around for the appliance and cables.

No...you don't know.

As I said, fuses in plugs are NOT for protecting the appliance or whatever is fed from the plug. It's to protect the wiring supplying it.

I think you will find that on each washing machine PCB there is a fuse which will aim to protect the circuitry of the machine. I've yet to come Across one that doesn't have one on the PCB.

Irrespective of this, if a fault develops which would blow a fuse it usually means the component which has developed the fault is knackered anyway and so whether the fuse is 13A or 4A it's going to still be broken. Your comments make me think that you believe a smaller fuse would stop a component from being damaged if it's short circuited or otherwise faulty which is a common misconception by people who don't know any better.

Go ahead and fit your under sized fuses. It won't do any harm but will mean you will potentially have a regular job to do replacing undersized fuses.

 

[bhm1712]

The average electric kettle draws 1800 watts, that is around 8A. A 10A fuse in the plug would do for that, yet 13A is in the plug.

Depends what the cable size is....if it's 13A then the cable will be 1.5mm regardless of the power rating of the element. Get it into your head that fuses in plugs protect cables not the item supplied.

 

[Ray Tay]

bhm1712, "Your comments make me think that you believe a smaller fuse would stop a component from being damaged if it's short circuited or otherwise faulty"

No I do not. The fuse will break ASAP before there may be a fire situation. The larger the fuse the longer it will smoulder.
Does the fuse on the pcb protect the heavy motor?

 

[Ray Tay]

bhm1712, I have it firmly in my head that fuses in plugs protect cables not the item supplied. In a kettle there is only one protection, the fuse. The old push out the plug protection I believe is rarely fitted in kettles these days - the lift off kettles that sit on a plinth.

 

[bhm1712]

bhm1712, "Your comments make me think that you believe a smaller fuse would stop a component from being damaged if it's short circuited or otherwise faulty"

No I do not. The fuse will break ASAP before there may be a fire situation. The larger the fuse the longer it will smoulder.
Does the fuse on the pcb protect the heavy motor?

No it won't.

Do you know how / what makes fuses actually blow?

If something is generating heat due to an
Electrical fault then it's not necessarily drawing the same current as what the fuse is rated to!

Sorry but your logic is seriously flawed/misguided.

 

[Ray Tay]

Every electrical course I have ever taken has always stated that appliance fuses must be rated to the appliance amps. Many here are say that does not apply. This is now rather confusing.

 

[bhm1712]

Every electrical course I have ever taken has always stated that appliance fuses must be rated to the appliance amps. Many here are say that does not apply. This is now rather confusing.

I seriously doubt it, but....

If so, then I'm seriously concerned by the course contents and providers.