First of all, I would run everything at high voltage to produce less heat and draw less amperage. If these are new servers, they should autosense the voltage. Secondly, you'll need to see how much va and amps each power supply will draw. Then you will match up the total va load with a little extra growing room, and also plugs on the back of the UPS to determine which model of PDU you will need. So for an example, if you have 15 servers with dual power supplies and each power supply draws 700W and 3.5Amps, you'll need 1000VA for each power supply connecting into a 16A or 24A PDU. So with a single 16A PDU, this will allow you to connect up to 4 power supplies (6 on a 24A, you do the math). Best thing to do is use a UPS selector like the one at APC's website. Put in the models of servers, how many power supplies, hard drives, etc..., state how long you want uptime (I believe minimum is 5 minutes) and if you want rack and/or redundant solutions and it will spit out a UPS solution (or state everthing has one power supply and multiply single solution by two). This will give you your power recepticle types to determine how many and which PDUs you will need (16A for the L6-20R and 24A for L6-30R).

You can plug the PDUs input to the UPSs output, no problem with that.
If you want the UPS to work with the backup generator it may be better if you choose On-Line UPSs (double or multiple conversion units).

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Joe
Electro-mechanic Engineering
jpm@ieee.org