Electrical question about fuses
Discussion
Can someone please explain to me why our slow cooker has 13Amp on the plug and yet when I opened it up to change the fuse it only had a 3amp fuse fitted?
I thought this maybe the reason it was not working as it had an underrated fuse fitted, so I found another appliance with 13amp on the plug to steal a fuse out of it and again it only had a 3amp fuse fitted, so figuring I must be misunderstanding the lettering I swapped the fuse into the slow cooker plug and it works fine so far, I fully admit that if there was not anything else lying around to rob a fuse out of I would have just gone and bought a 13amp fuse for the slow cooker and presumably ran the risk of it setting the kitchen on fire if it overheated.
Can anyone explain to me why this is? I fully admit to not knowing an awful lot about electrics and so must have a gap in my already basic knowledge.
Ta
I thought this maybe the reason it was not working as it had an underrated fuse fitted, so I found another appliance with 13amp on the plug to steal a fuse out of it and again it only had a 3amp fuse fitted, so figuring I must be misunderstanding the lettering I swapped the fuse into the slow cooker plug and it works fine so far, I fully admit that if there was not anything else lying around to rob a fuse out of I would have just gone and bought a 13amp fuse for the slow cooker and presumably ran the risk of it setting the kitchen on fire if it overheated.
Can anyone explain to me why this is? I fully admit to not knowing an awful lot about electrics and so must have a gap in my already basic knowledge.
Ta
The plug has a maximum rating of 13amp, but the fuse should be rated to suit the appliance. To find the rating for the appliance; divide the loading (eg,1000wats) of the appliance by 240volts, this will then give you the correct fuse rating.
Edited to make more sense (I hope).
Edited to make more sense (I hope).
Edited by robinhood21 on Saturday 18th October 16:55
Hi,
13amp plugs have a sticker saying 13amp because usually they will come with
a 13amp fuse if the plug is purchased on its own to attach to an appliance.
However they can also be supplid with a 3amp fuse as standard. I think your
plug once had a 13amp fuse and its been changed to a 3amp.
The fuse in the plug is related to the load of the appliance i.e the wattage
required to run the appliance. This is not related to the plug itself which
can be used up to a maximum of 13amp or roughly 3100 watts.
Have a look at the wattage of you slow cooker. For a 3 amp fuse it should be
750w or less.
Hope that helps.
13amp plugs have a sticker saying 13amp because usually they will come with
a 13amp fuse if the plug is purchased on its own to attach to an appliance.
However they can also be supplid with a 3amp fuse as standard. I think your
plug once had a 13amp fuse and its been changed to a 3amp.
The fuse in the plug is related to the load of the appliance i.e the wattage
required to run the appliance. This is not related to the plug itself which
can be used up to a maximum of 13amp or roughly 3100 watts.
Have a look at the wattage of you slow cooker. For a 3 amp fuse it should be
750w or less.
Hope that helps.
robinhood21 said:
The plug has a maximum rating of 13amp, but the fuse should be rated to suit the appliance. To find the rating for the appliance; divide the amperage of the appliance into 240volts, this will then give you the correct fuse rating.
I just cant type that fast, you must have alterd it as i typedEdited by marc.l on Saturday 18th October 17:02
marc.l said:
robinhood21 said:
The plug has a maximum rating of 13amp, but the fuse should be rated to suit the appliance. To find the rating for the appliance; divide the amperage of the appliance into 240volts, this will then give you the correct fuse rating.
Dont think thats right. I think its volts devided by Watts the appliance uses equals the Amps
The plug is a 13a one, maximum current I think, you then have the option to use fuses of varying sizes to match the Wattage of the item being powered, this is normally in the manual of the item which states what size fuse you need, I am sure on of the resident sparkies will be along shortly.
http://en.wikipedia.org/wiki/Electrical_fuse
http://en.wikipedia.org/wiki/Electrical_fuse
JackDaniels said:
...our slow cooker has 13Amp on the plug and yet when I opened it up to change the fuse it only had a 3amp fuse fitted?
Has it actually got a little sticker on, saying 'fitted with a 13 amp fuse', or are you just talking about the letters moulded into the plastic of the plug itself that say '13 amp'?All conventional UK 3-pin plugs are rated for 13 amps maximum, but the fuse that is fitted should be specific to the appliance. Usuallty (but don't rely on it) the manufacturer will put a separate sticker on saying what fuse should be fitted.
A (flawed) analogy is that Ford might build a car with engine sizes from 1.2 litres up to 2.5 litres. The body of the car has been 'rated' to be safe up to 2.5 litres, but the actual engine size fitted will depend on your specific needs...
If the appliance was fitted with a 3 amp fuse, then that's what you should replace a blown fuse with. Fuses are there to prevent the appliance drawing more than its designed level of current if a fault develops. If you fit too heavy a fuse, you're removing part of that protection and the appliance might burn something out and become dangerous before the fuse blows!
You got it!robinhood21 said:
The plug has a maximum rating of 13amp, but the fuse should be rated to suit the appliance. To find the rating for the appliance; divide the loading (eg,1000wats) of the appliance by 240volts, this will then give you the correct fuse rating.
Edited to make more sense (I hope).
Correct, except use v = 230 volts now. UKEdited to make more sense (I hope).
Edited by robinhood21 on Saturday 18th October 16:55
harmonised supply level is now 230 v, no longer 240v. Use the formula
I= P/V.
EX/
eg: if the appliance was eg 2300 KW ?
Divide by supply voltage 230 V
Therefore the current being drawn, in this case
would be 10 AMPS .
In your case substitute the wattage of your appliance and divide
by 230..........that will give you the normal operating current .
( I'm an electrical eng )
Edited by jag guru on Saturday 18th October 17:30
Was the 3 amp fuse blown? If not, then fitting a bigger fuse should achieve nothing.
If it was blown, and it is original, the correct fuse, then replace it with a 3 amp fuse, not a 13 amp fuse.
Fitting a 13 amp fuse to a gadget designed for a 3 amp fuse is akin to using a short length of six inch nail as a fuse: it'll work, but there's a definite reason you shouldn't do it.
Of course you won't find this out until the gadget has shorted out, self incinerated, and burned your maison to the ground.
If it was blown, and it is original, the correct fuse, then replace it with a 3 amp fuse, not a 13 amp fuse.
Fitting a 13 amp fuse to a gadget designed for a 3 amp fuse is akin to using a short length of six inch nail as a fuse: it'll work, but there's a definite reason you shouldn't do it.
Of course you won't find this out until the gadget has shorted out, self incinerated, and burned your maison to the ground.
Important!
Do not fit a higher rated fuse than necessary as the fuse is only there to protect the cable - otherwise the cable becomes the fuse.
ie: if you have 500W (call it 2Amps) appliance fed by a weedy cable and you put a 13A fuse in the plug then, if the appliance develops a fault, the cable will likely melt before the fuse blows and could cause a fire.
Do not fit a higher rated fuse than necessary as the fuse is only there to protect the cable - otherwise the cable becomes the fuse.
ie: if you have 500W (call it 2Amps) appliance fed by a weedy cable and you put a 13A fuse in the plug then, if the appliance develops a fault, the cable will likely melt before the fuse blows and could cause a fire.
mrsxllifts said:
jag guru said:
Correct, except use v = 230 volts now. UK harmonised supply level is now 230 v, no longer 240v.
230V, my a
e! Round here its anything from 210V to 255V! You don't need dimmer switches, they change like mood lighting on there own! Hannah !
Did you take into account the power factor of the unit?
Realistically, the slow cooker is going to be rated at something like 1Kw, therefore, you need a 5A fuse to be correct, which will give you a max load of 5A x 230V = 1150W. HOWEVER, while our voltage is 230v, this is a NOMINAL voltage, and it could be as low as 193V.
If the power consumption is constant, and the voltage falls, the current will increase.
Consequently a slow cooker is a passive resistive heating element, thermostatically controlled, and it's output will rise/fall with the voltage, following the V=IR, where R is fixed as the resistance of the heating element.
(I could get pedantic and say impedance rather than resistance because this is a AC circuit, and there will be some form of inductance in the circut, but that will make the calculations more complex bringing power factors into the mix, but let's not get into an Electrical Principles lesson here).
Realistically, the slow cooker is going to be rated at something like 1Kw, therefore, you need a 5A fuse to be correct, which will give you a max load of 5A x 230V = 1150W. HOWEVER, while our voltage is 230v, this is a NOMINAL voltage, and it could be as low as 193V.
If the power consumption is constant, and the voltage falls, the current will increase.
Consequently a slow cooker is a passive resistive heating element, thermostatically controlled, and it's output will rise/fall with the voltage, following the V=IR, where R is fixed as the resistance of the heating element.
(I could get pedantic and say impedance rather than resistance because this is a AC circuit, and there will be some form of inductance in the circut, but that will make the calculations more complex bringing power factors into the mix, but let's not get into an Electrical Principles lesson here).
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