My question is why the need to oversize the neutral, 240 volt residential, the neutral will the 'difference ' of the two legs, ie 20 on A and 25 on B then the total on the nutral will be 5 amps.
The heaters are generally 240 volts on both and the neutral is not involved, balance.
What am I missing here, it doesnt make sense to oversize the neutral in this case.
Right ???!!

-Mark-