OK, back to 'motor basics' time.
To size your wire, go by the tables in the NEC (430.250 or thereabouts), using the value closest to the actual voltage. For example, the chart might say 16 amps, while the motor is marked 12 amps; size the wire for 16 amps.
To size your breakers and heaters, start with the nameplate FLA, then measure your actual needs, and adjust from there.
For example ... in the nameplate says 12FLA, Start with 20 amp breakers (175% of 12)and size the heaters for 16 amps (140% of 12).
Now, run the motor as intended, and measure. Also see if there are operation problems. It's very possible, in this example, that you'll have to increase the breaker to 25 amps, yet be able reduce the heaters to 10 amps. It's all a matter of starting current, and actual load.
One cannot over-state the importance of the nameplate! I recently came across an installation where the NEC tables said 6.6 amps - yet the motors were marked 10 amps! This is a rare case of the motor maker under-stating the size of his motors. Simply saying "they're 1-1/2 hp motors" isn't enough .... look for the nameplate!