I am investigating the idea of building out my own datacenter, and I
need to understand some 3-phase power concepts to help me estimate
certain costs.

I know I will need 3-phase power because the UPS and AC unit will either be 208V 3-phase, or 460V 3-phase.

My problem is I am confused as to how I calculate power usage, power costs, and sizing.

So to start with, if I get 208V 3-phase 225amp. Is it 225 amp on each phase, or is it 75amps on each phase, adding up to 225amp total?

Beside the AC equipment, everything below the UPS will be 120V single phase. So if I want to find out the cost of running 40 amps of 120V single phase equipment, 40A*120V = 4800VA = 4.8KW. Its a datacenter, so everything runs 24x7. At $0.05 per KWhr, that 40 amps of 120V equipment will cost $5.76 per day.

But how do I size and compute the cost of the 3-phase AC units. For example, a 10-ton liebert is 460V 3-phase, and claims to draw 40amps. But 40amps of what? 40amps per phase, or 40amps in total across all three phases? So is it 460V

And finally the price per KWhr. Is that per phase, or for all three phases?

I know these seem like dumb questions, but it would really help me to understand better. I would like to understand this so I can compute my monthly power costs for all my equipment.

thanks john

I know I will need 3-phase power because the UPS and AC unit will either be 208V 3-phase, or 460V 3-phase.

My problem is I am confused as to how I calculate power usage, power costs, and sizing.

So to start with, if I get 208V 3-phase 225amp. Is it 225 amp on each phase, or is it 75amps on each phase, adding up to 225amp total?

Beside the AC equipment, everything below the UPS will be 120V single phase. So if I want to find out the cost of running 40 amps of 120V single phase equipment, 40A*120V = 4800VA = 4.8KW. Its a datacenter, so everything runs 24x7. At $0.05 per KWhr, that 40 amps of 120V equipment will cost $5.76 per day.

But how do I size and compute the cost of the 3-phase AC units. For example, a 10-ton liebert is 460V 3-phase, and claims to draw 40amps. But 40amps of what? 40amps per phase, or 40amps in total across all three phases? So is it 460V

***40A or 460V***40A*3.And finally the price per KWhr. Is that per phase, or for all three phases?

I know these seem like dumb questions, but it would really help me to understand better. I would like to understand this so I can compute my monthly power costs for all my equipment.

thanks john