The specs say:
Standard voltage options
208 VAC, 3 phase, 60 Hz
240 VAC, 3 phase, 60 Hz
208 VAC, 1 phase, 60 Hz ( 20 & 30 gallon models only)
240 VAC, 1 phase, 60 Hz ( 20 & 30 gallon models only
This is the 30 gallon model we're talking about here. So it looks like it CAN be 1 phase...