Which UPS for 3 phase power and 3 PSUs?

[Anonymous user]

I am newbie to 3 phase power and blade servers. I have a question on what UPS configuration would work with 3 phase power and a Dell 1000E blade server

I am assisting the install of the Dell M1000E blade chassis and 10 eight core blades. This machine will run close to 90% utilization 24/7. Per Dell's recommendation we will be installing a 208v 30 amp 3 phase wall connection. This wall connection will connect to a 24 amp three phase PDU. From the PDU, 3 power cords will connect to the 3 PSUs in the blade chassis. Each PSU is capable of delivering 2360 watts.

I need a UPS for this system that does not break the bank. A single UPS for all three PSUs is cost prohibitive. I was hoping to use 3 UPSs and connect one to each PSU. Can I have a setup that goes PSU to 3000va UPS to 3 phase PDU? Does the UPS need to be specifially 3 phase - do bad things happen when you connect a single phase UPS to a 3 phase PDU? The PDU and PSU use C19/C20 connectors and a lot of UPSs use NEMA L6-30 connectors? Can I use adapters to connect everything together?

Thanks,
Mike

[BillP]

Hi Mike,

I want to make sure I have a clear understanding of your setup.

Your going to have 3 blade chases. Each will have 1 PSU. Each PSU will pull a max of 2360 Watts. Each PSU is single phase 208V.

Assuming this is correct I sized the 2360W on the sizing tool (http://apc.com/tools/ups_selector/index.cfm) and it suggested the SURT6000XLT as the best price option, the Symmetra LX 8K (SYA8K8P) as the best value and the Symmetra LX 8K (SYA8K16P) for best performance. You should check all of these out and see what you think. All have expandable run time but only the SYA8K16P can be expanded for higher VA output. The Symmetra's allow for redundancy internal to the chaise with additional power modules.

As for connecting single phase UPSs to 3 phase power it should be fine. You will want to be sure to balance the 3 legs. If it gets out of balance you could get a high impedance neutral. Also if the legs get to far out of balance then it could cause the units to show site wiring faults or even run off of battery and cut off from the utility power.

You may also want to consider a 3 phase UPS. the Smart-UPS VT line is not as modular as a Symmetra but is priced very well. The Symmetra PX cost more but it is the premium solution for what you are looking for.

I wouldn't start buying any of this yet though. If you call into sales they can have someone call you to size this appropriately and make sure everything is covered.

I hope this helps.

[Anonymous user]

Thanks for the reply. Actually we have one blade chasis and 3 PSUs in that blade chasis. However, the three PSUs all have their own C20 connectors so I think we can treat them independently for sizing purposes.

1) It sounds like I can use a single phase UPS on a three phase PDU. Do I need a special 3 phase PDU that splits 3 phase into single phase for each outlet? If so, any suggestions on model numbers?

2) From a cost standpoint, I think I can save a little money and have some redundancy if I buy 3 APC SUA3000XL UPSs. One UPS for each PSU. Does this sounds ok or should I go with the SURT6000XLT?

By the way, the 2360w PSUs can theoretically draw 14amps in a worst case scenario (although I think Dell exagerates this).

Thanks again. I will also call into sales.

Best,
Mike

[BillP · Accepted solution]

Hi Mike,

For the C20 you may need to get special cables. If Dell can't provide them for you we have them for sale on our web site: http://www.apc.com/products/family/index.cfm?id=122.

What you need for PDUs will depend on what UPS you go with and its input. You could have the 3 phase going into a panel then split it and hard wire in each of the UPSs (best way for anything 5000 VA or over), this also eliminates a possible point of failure in the PDU. You could also use a PDU that splits the phases, but you will have to figure out what UPS you want first to determine what outlets to order. Here is a list of the PDUs, you will probable want to look at either the 208 3ph with L6-30. http://www.apc.com/products/family/index.cfm?id=30.

I'm assuming the PSUs run off 208V. If they say it can draw 14 amps then I would size for that + about 20% (check the electric code in your area to be sure of wiring and breaker sizes). 14 amps puts you around 2912 Watts at 208V. If you have redundant PSUs in that chaise then you have to consider the possibility of either 2 UPS failing or 2 of the 3 phases failing. If this were to happen you would almost assuredly max the 3rd out. So again I would size slightly larger per PSU to be safe. In this case the SUA3000XL has 2 down falls. 1, only 2700 Watts output and 2, only 120V output.

Another key point to consider is how much run time you want. All the SURT, Smart-UPS XL, Smart-UPS VT and Symmetra lines can have extra batteries attached to extend run time when on battery. Do you have a generator that will be starting up? If you do then the size of the generator will also have to ne considered.

If you really want to be sure about what your getting and if it will work, I would call our sales department to be safe. We work with Dell regularly and should be ably to size it how ever you want (1 or 3 UPS) and give you options in whatever price range you are looking at.

Let me know what you think and/or decide to go with.

Message was edited by: PowerMan