Whoa!
I cincerely hope the 40A rating was for 120V single phase (2 parallelled coil series) hookup, cranking out some 4,8 kW
(didn't it take app 2 hrs to heat up to 2 000 F? Guess you'd certainly see if it took 9,6 kW - your house would probably "brown out" a bit).
If you'd (I assume) hooked these coils in series, and feed them 240 V, they'll still just crank out those 4,8 kilowatts, but only suck 20 amps per phase.
Did you even hook the two coils' mid points to neutral (kinda missed to see that in your über-fast hookup)?
You could easily measure the max current of each phase with a cheap clamp ammeter.
Good thing to mount a fan to the cooling fins...

I might be mistaken here - but aren't the US 240 VAC actually "only" 2 phases, each at 120 VAC & 180 degrees apart?
Over here in (most of Europe) we use the 230 VAC between phase and neutral - and the three phases are 120 deg apart,
achieving 400V AC between two phases, hence the "230/ 400 VAC" system desctriptor.

Good luck and keep up the good work!
Cheers
Johan