208V vs 240V

Both 208V and 240V are nominal 'two-hot' voltages used to power ASIC miners, but they come from different electrical services, and the distinction has real consequences for efficiency and equipment selection. 240V is the phase-to-phase voltage of a single-phase, three-wire system, the kind typically delivered to homes. 208V is the phase-to-phase voltage derived from a three-phase, 120/208V wye system, the standard commercial service in much of North America.

Where the numbers come from

In a 120/208V wye, each phase measures 120V to neutral. Because the three phases are 120 electrical degrees apart, the voltage between any two of them is not 240V but 120 multiplied by the square root of three (1.732), which equals about 208V. So 208V is roughly 13% lower than 240V (208/240 is approximately 0.866). A miner running 'between two hots' in a commercial building therefore sees 208V, while the same machine in a home on split-phase sees 240V.

Why miners should care

For a fixed-power load, lower voltage means proportionally higher current to deliver the same wattage, which increases conductor heating and I-squared-R losses, and many supplies run marginally more efficiently at 240V than at 208V. ASIC PSUs are usually wide-input (typically 200-277V) and will run on either, but nameplate ratings, breaker sizing, and cable gauge must be computed at the actual service voltage. Sizing a circuit assuming 240V when the building delivers 208V undercounts the current draw.

Practical takeaway

Confirm whether a site is single-phase 240V or three-phase 208V before specifying breakers, whips, and PDUs. The gap is small in volts but meaningful in current and heat at scale.

For the underlying transformer geometry see Wye vs Delta wiring, and for the home outlets that deliver 240V see the NEMA 14-50 receptacle.

Check PSU input ranges in the ASIC PSU reference.