need help with 3-phase measuring and billing

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*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
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On 5/23/07 9:47 PM, in article snipped-for-privacy@p47g2000hsd.googlegroups.com, "essenz"

It is 225A on each conductor irrespective of how it is connected.
Basically you pay for the energy consumed. There may be surcharges for poor power factor, poor form factor, demand, time of day etc. Contact you power supplier.
It really would be worth paying someone to do the calculations and planning. It is clear that without further education on the subject, you can get yourself into lots of trouble.
Bill -- Fermez le Bush--about two years to go.
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225 A per phase.

Or less, if power factor is lower due to displacement and/or distortion (harmonics). You could ignore this if you like. It will be a source of error.

40 A sounds high for 10 tons at 460 V 3 phase. Generally consider 1 ton of a/c to be 1 kVA. Mathematically, 40 A is 40 A per phase and the calculation for three phase would be 40 A * 460 V * 1.732 = 32 kVA. 1.732 is the square root of three and it is used this way for three phase power. It is equivalent to calculating it like three individual lines: 270 V * 40 A * 3 = 32 kVA. Large motorized equipment Watts will generally be about 90% of the VA at full load due to 'power factor'. Your a/c probably won't run full out 24/7.

That is per kWh and 'per phase' or 'for all three phases' may not be meaningful. Find your total kWh consumed and multiply by the rate. It will include all three phases.

Good luck.

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Need help understanding a bill. The space I will going into has 460V 3- phase 200amp provided by the building. They meter it and charge accordingly. To get an idea of pricing, building mgmt sent me a sample bill from another customer.
The bills says, BILLED DEMAND 36.8KW, then lists the metered KWH, which is 16193 KWH. Then it lists the charge for 16193 KWH, which is \$1843.00 US. I am a little confused by this, because on the surface, it appears to be \$1843 for 16193 KWH - which comes to 11 cents per KWH - which seems very high.
Can anyone comment on this. Building says the charge the GS rate. Building is located in Philadelphia, PA.
My 120V equipment will be running 24x7, 16193 KWH, 24x7 for 30 days, is only around 18 KW of equipment, or 150amps of 120V. That seems very high cost. But maybe I am reading the bill wrong, maybe its 16193 KWH for all 3 phases?!
Thanks john

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| Need help understanding a bill. The space I will going into has 460V 3- | phase 200amp provided by the building. They meter it and charge | accordingly. To get an idea of pricing, building mgmt sent me a sample | bill from another customer. | | The bills says, BILLED DEMAND 36.8KW, then lists the metered KWH, | which is 16193 KWH. Then it lists the charge for 16193 KWH, which is | \$1843.00 US. I am a little confused by this, because on the surface, | it appears to be \$1843 for 16193 KWH - which comes to 11 cents per KWH | - which seems very high. | | Can anyone comment on this. Building says the charge the GS rate. | Building is located in Philadelphia, PA. | | My 120V equipment will be running 24x7, 16193 KWH, 24x7 for 30 days, | is only around 18 KW of equipment, or 150amps of 120V. That seems very | high cost. But maybe I am reading the bill wrong, maybe its 16193 KWH | for all 3 phases?!
The kWH amount is the total power used, regardless of which phase is involved. If the load was perfectly balanced in phase usage, then exactly 1/3 of that power would be used on each phase. if it is not balanced, then more on one and/or less on another.
GS = General Service ... i.e. for commercial usage, not residential. It does cost more. Visit your power utility web site and search for the billing tariffs or equivalent documents.
If your 120V equipment is single phase, try to keep it all in balance over the three phases the best you can. Your electrician can help you identify which circuits are on which phase. I assume the building has a stepdown transformer, probably a three phase one. The voltage could be 460 in, 200/115 out, or 480 in, 208/120 out.
200 amp service on 460 volts is a total of 159 kW. At 480 volts it is 166 kW. You can get a maximum of 1/3 of that on each phase.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |