Given the last post has been closed I'd like to continue the thread, without the bun fight, if I may.
Tis true that the common element, pardon the pun, in basic electrical calculations is the resistance of the element.
But how do you assess that resistance accurately when most appliances are rated to run happily between 220V - 240V and the supply could have a supply voltage of anywhere between 216V - 254V ? with the added bonus that most appliances now are manufactured abroad and conform to the European EN standards of 220V
Coupled with that. You could measure the resistance of the heating element with an Ohmmeter, but that would be the cold resistance. We know from the temperature coefficient of resistance that resistance increases with temperature so the hot power rating will also change!
Given that there are too many variables to make an accurate assessment, we would have to take a probable average using the nominal voltage and the power rating given on the package.
With that in mind we have R = V^2/P = 230^2 / 8500 = 6.22 Ohms and a current flow of 37A
However, what if the actual supply voltage, such as we find in many TT installations, as an example is 245V?
We now have a current flow of 39.4A
Assuming this as a worst case the power of the appliance is now 9.7kW !
Given that the fusing factor for overload for a 32A breaker is quoted as 1.13, the maximum allowable current that would flow for a given period of time would be 36A. So we are now running hot. Not so bad if you can guarantee that the usage was limited to about 10 minutes or so.
The reason why I mention this is that I once went to see a job where the granddaughter had been using a newly installed shower of unknown rating from a 30A fuse carrier supplied by a cable unknown and had blown the fuse. When I questioned the woman about the installation it was obvious the new shower was installed by a person of unknown/dubious professional qualification with her blessing. I suggested that as a council tenant she should contact the council's clerk of works and at that point I left.
Tis true that the common element, pardon the pun, in basic electrical calculations is the resistance of the element.
But how do you assess that resistance accurately when most appliances are rated to run happily between 220V - 240V and the supply could have a supply voltage of anywhere between 216V - 254V ? with the added bonus that most appliances now are manufactured abroad and conform to the European EN standards of 220V
Coupled with that. You could measure the resistance of the heating element with an Ohmmeter, but that would be the cold resistance. We know from the temperature coefficient of resistance that resistance increases with temperature so the hot power rating will also change!
Given that there are too many variables to make an accurate assessment, we would have to take a probable average using the nominal voltage and the power rating given on the package.
With that in mind we have R = V^2/P = 230^2 / 8500 = 6.22 Ohms and a current flow of 37A
However, what if the actual supply voltage, such as we find in many TT installations, as an example is 245V?
We now have a current flow of 39.4A
Assuming this as a worst case the power of the appliance is now 9.7kW !
Given that the fusing factor for overload for a 32A breaker is quoted as 1.13, the maximum allowable current that would flow for a given period of time would be 36A. So we are now running hot. Not so bad if you can guarantee that the usage was limited to about 10 minutes or so.
The reason why I mention this is that I once went to see a job where the granddaughter had been using a newly installed shower of unknown rating from a 30A fuse carrier supplied by a cable unknown and had blown the fuse. When I questioned the woman about the installation it was obvious the new shower was installed by a person of unknown/dubious professional qualification with her blessing. I suggested that as a council tenant she should contact the council's clerk of works and at that point I left.
