Watts & Volts in Household Appliances

T

Ted Flanders

Guest
An appliance uses (for example) 800 Watts, and uses a 3 Amp fuse.

Therefore, do all household appliances of 800 Watts use the same fuse, or do different appliances of the same wattage sometimes require different sizes of fuse?

Would an appliance of 800W with a 3 Amp fuse, use *less* electricity than an appliance of 800W which requires a 12 Amp fuse?
 
Okay this brings me back to my InterCert(!) Physics days. Wattage = Ampage x Voltage. In Ireland we use 220V electricity and say you use a radio rated 110 W you would need to use a fuse of at least 110/220 Amps (0.5 amps). However a 3 or 10 or 12 A fuse will work with it .However if you use a 3A fuse with an electric heater rated 2200W it will blow as it needs a fuse rated 10 (2200/220) A or more. Usage of electricity is related to to Wattage rating of an item not the fuse rating. In other words the heater uses 20 times more electricity that the radio. And hence you could run a radio 20 times longer than the heater for the same cost.
 
Hi hansov, nice calculations, but for future reference we are now using 230volts.

Ted, the fuse is only there to protect the cable. Small 0.75mm cable uses 3amp fuse. This basically means that in the event of a fault, the fuse should blow and isolate the circuit, before the cable, after it sustains damage.

All 800watt appliances use the same amount of power (which is what you pay for) irrelevant of the fuse rating, which is for protection only.
 
Dont forget about the Power Factor

Does not apply to your heater example ( power factor is 1 ) but does for things like electric motors ( fridges ) and DC power supplies ( PCs )

VA = Volts X Amps

Watts = VA X Power Factor
 
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