I might be wrong but I think that you are missing a point .
If you want to get 100 Watt from a 48 Watt resistance you will overheat the resistance and in a short time it will burn.
If you want to go directly with 230 Volts in a large heating plate with the size and pattern you prefer you should go with this solution :
[forums.reprap.org]
If you want to get 100 Watt from a 48 Watt resistance you will overheat the resistance and in a short time it will burn.
If you want to go directly with 230 Volts in a large heating plate with the size and pattern you prefer you should go with this solution :
[forums.reprap.org]