Is the power distribution panel 3 phase as well? If so here's the math

Watts / volts x 1.732

that's how you get amperage draw if you place a single miner across each phase

1400w / 240 x 1.732 = 10.1 amps

400 / 10.1 = 39.6

39 (round down) x 3 = 117 miners