208v 3 ph will power how many 120v 4kW cabinets?

It should be a 120/208 volt UPS, to have the 120 volt available your looking for.

4000 watts at 120 volt is a 40 amp circuit, and cannot use 20 amp receptacles on a 40 amp circuit. This would waste available power.

What size circuit is planned for each rack? Keep in mind, each circuit cannot be loaded more than 80% of the circuit rating.

A 180 kW 120/208 3 phase volt power source will provide 500 amps per phase or 60,000 watts.

Simple answer to you question is 60,000 / 4000 watts is 15 120 volt 40 amp circuits each phase, or 45 total 120 volt circuits, or 45 racks.

Assuming your correct in that you plan to serve each rack with a 40 amp 120 volt circuit, how is this power distributed in each rack?

I have done several data-centers or rooms. Most racks get either 208 volt single phase or 3 phase delivered, typically 30 or 60 amps. I have not done a 120 volt circuit to one rack for years.

4kW seems small for one rack. With the Blade Server, IT techs have been able to populate one rack with much more servers than in the past, thus making the one 120 volt circuit to one rack an thing of the past.

Which came first, the chicken or the egg? Is the UPS new and the racks are existing, or otherwise?

Are your servers rated only 120 volts? Most I have seen for the last several years are able to take 208 volt single phase, or a 3 phase 208 volt circuit to the rack and a single phase PDU strip in the rack providing the 208 V receptacles.

Something does not seem right, based on your question and information provided, and how datarooms have been typically done recently.

Also, I am sure you have considered cooling for this space based on the heat load of the total devices?

I agree something does not seem right, and TK is obviously very knowledgeable in this, but I would think with equipment this big (and expensive) you'd have engineers at your disposal to figure this out.

Thanks for the responses. We're thinking two 20 amp circuits per cabinet; 4.8 kw per cabinet ( 80% usable = 3.85 kW). The calculation of phases throws me off. Is it 500 amps for each of three phases? Or do I figure 500 * 1.73 to get the total available amps I can distribute via 120v 20 amp circuits.
Yes, we can run servers at 208v for better efficiency. In that case, we can live with a single 208v 30 amp drop per cabinet.
The expert response indicated we'd have 500 a X 3 phases = 1500 amp total. So does that mean we'd be able to pull fifty 208v 30 amp circuits? Even at 80% utilization that would give me 40 208v 30 amp circuits.
We have 2,500 sf of space w 30T and two 10T Liebert CRACs; and 180 kW UPS with 750 kW diesel backup.

Thank you all for the expert advice. I'm double - checking my electrician who told me 15 cabinets, but it seems like he didn't account for the three phases. At 15 cabs the project doesn't work, but if more than 30 cabs then it is a great project!

Do not do the calc "500 * 1.73", it is irrelevant.

The correct calc is KW= E*I*1.73, or I= KW/E*1.73 , or 180000 / 208 * 1.73 = 500 amps per phase, before derating 80%.

I strongly suggest you use 208 volts to each rack, for several reasons.

Fist we need to understand what is the total available capacity of the UPS.

Is it 180kW ? Where does the 200 kW come in?

If the unit is fully rated at 200 kW, and derated 80%, that leaves 160 kW.

If a 30 amp 208 volt circuit is at each rack, how will that be distributed?