We have a comet extreme 4.5 kva. It has 2 PDU's attached to it. Does anyone know if we can connect a third one?
It all depends on your load. What is your load. Most likely the UPS has a capacity just over 3kW. I doubt the 4.5KVA UPS will be able to support an additional PDU and still maintain your load without the UPS system going into internal bypass. When you go into internal bypass, you no longer have a UPS system and you have an expensive switch connecting you directly to the Utility power.
you can connect n number of PDUs. the number is not a concern. you have to worry abt the load. if a single PDU is draining all the power from the UPS, u cannot even connect the second PDU. you have to calculate how much power is utilised by the two PDUs you have presently connected and see if you can accommodate one more.