you should go to i higher voltage, as the Rumba mosfet also supports higher voltages on the Board-switch, this will reduce your ampere taken from the board.
with such a large bed you should at least use six powerresistors otherwhise you only get some hot-spots where the bed is reaching it`s temperature, especially the corners will be very cold.
so there should be a resistor near every corner at least, and some in the middle.
I´m using some foil heates for my 300x360 heatbed, although they are reated for 12V i`m powering them with a 230W 19V notebook powersupply, you just have to calulate what power they take at 19V.
The resistance may become very low which may cause a safe shutdown to the powersupply when heating up from cold, so i made a serial/parallel switch to first warm up to 35°C and after that switch to parallel to heat up with all power.
How is the Bed mounted on the printer (what printertype), normally the holes of a Printbed are in the corners and not in the center ?????
Chri
with such a large bed you should at least use six powerresistors otherwhise you only get some hot-spots where the bed is reaching it`s temperature, especially the corners will be very cold.
so there should be a resistor near every corner at least, and some in the middle.
I´m using some foil heates for my 300x360 heatbed, although they are reated for 12V i`m powering them with a 230W 19V notebook powersupply, you just have to calulate what power they take at 19V.
The resistance may become very low which may cause a safe shutdown to the powersupply when heating up from cold, so i made a serial/parallel switch to first warm up to 35°C and after that switch to parallel to heat up with all power.
How is the Bed mounted on the printer (what printertype), normally the holes of a Printbed are in the corners and not in the center ?????
Chri