It’s a custom job for me. Tho’ I suppose it MIGHT be marketable to have a 4 heat setting heater? In any event, such diode control is used in some (maybe 20% of the market?)
floor standing space heaters.
I would tell you, but then I’d want a cut of whatever market you manage to corner....😁
The only rectifier I ever built was a 4-diode full wave to charge my battery when the voltage regulator in my Fiat went out - and I would have had to buy a while new alternator to replace it - just used the biggest diodes I could find in our bench stock....