Can I run 280 volts to a 230 volt heating coil on an industrial oven ? And will a series of 3 of these elements produce more heat than a series of 2 of these elements put together ? I currently have 6 elements and they are wired as two series of three but they are not putting out much heat, So could I wire them into 3 series of two to produce more heat. My oven takes way to long to get up to temp. These are brand new elements they sent me for this particular oven.
Any and all help would greatly be appreciated!!

All good questions for a conversation with the manufacturer...

Theoretically much is possible although changes that you suggest would likely
Void warranties, the electrical code and may be a hazard...