Andy:
Wouldnt this be considered a continuous load?
210.20(A). So if your load is 198 amps with that kind of load the conductors could also be used as heaters (?)
Just by that the rating should be 247 amps or 125% of the load + the non-continuous load. Also art. 424.3(B) Branch circuits, fixed electric space heating equipment, shall be rated at 125 % of total load and motors.
I would think you need a bigger panel.
