When determining what capacity the UPS needs to have when it’s going to backup equipment with redundant power supplies, the number of power supplies in the redundancy scheme is not a contributing factor. The total number of watts that the PSU is rated for is the only one that needs to be considered. What does need to be taken into account is the number of outlets available on the UPS so that it matches with the number of power cords needed to connect to the server(s). Although you’re only considering 1xPSU for the UPS capacity, you need to count 2xPower cords, 1 for each PSU. A PDU may be needed to distribute the UPS power to add more outlets than when what the UPS has.
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To figure out the correct UPS I would need to know some more information. For example what available outlets do you have to plug the UPS into? For example you have 6 (servers) x750w (PSU) = watts. If you have a 208V system available a CyberPower OL6KRT UPS will cover your total wattage. If you only have 120V system left then the amount of UPS’s will depend on the amperage you have available in your server room. For example if you have a 15A system available then you would need Qty 3 PRLCDRTXL2U to cover the total wattage. If you have a 20A system then Qty 3 PRLCDRTXL2U, but you will have some spare capacity if you want to add some more equipment. If you have a 30A system available then you would need qty 2 PRLCDRTXL2U to cover the total wattage. So it comes down to what you have available in plug your UPS’s into as to qty you will need. Sorry this is so long I just wanted to make sure you had all the info. If you would like some more help choosing a UPS or have any questions feel free to message me. Thanks.
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Here is a runtime chart for Smart-UPS. You may need something of a higher product line, though. I can never find these charts by browsing their site - I just randomly found it.
https://www.apc.com/products/runtime_for_extendedruntime.cfm?upsfamily=165&ISOCountryCode=us
It would be great if someone from APC or a similar vendor can chime in (and correct me if I am wrong), but I think you need to make sure that whatever you pick can handle the load equivalent to W (which is the max power draw of 1 power supply from each server), and have a redundant UPS for the redundant power supplies. If you plug both of your redundant power supplies into the same UPS, then your server goes down if you shut down your UPS by mistake, or the UPS dies.
Runtime is going to be based on your actual normal power draw, which may be more like W, maybe more or less. Also, your redundant power supplies likely don’t draw the same amount of power - one could sort of be in a standby mode. The vendors should be able to direct you to the appropriate charts for the product lines you should be looking at.
If going with APC, and the SmartUPS are not beefy enough to go with 2 units because they cannot support the load, then you could go with 4 units and have 3 servers connected to 1 redundant pair of UPS’s and the other 3 to the other redundant pair of UPS’s
Maybe the really beefy UPS units do something better that I don’t know about that makes them more cost effective, but they have always been outside of my budget.
Hi Eli,
If you can determine the actual power draw of the servers, that is always the best way to calculate UPS needs. I checked Dell’s website and the power consumption they list for this server is higher than the power supplies you listed, so I suspect that is based on a higher wattage power supply than you have. Without the actual power consumption, using the power supply rating would be the next best option as this ensures the UPS can handle the maximum draw of the servers. It also would be helpful to know what plug types you need as well as whether you prefer rack mount or stand alone tower style UPS units. Based on a maximum power draw of watts, the best UPS solution for at least 10 minutes of run time would be our Smart-UPS SRT VA with 208/240V to 120V Step-Down Transformer (APC model number SRT6KXLT-5KTF) and one SRT192BP Battery Unit. The SRT6KXLT-5KTF would be at approximately 75% of its capacity and with the external SRT192BP Battery Unit you would receive approximately 21 minutes of runtime. I have linked the SRT6KXLT-5KTF) and SRT192BP Battery Unit below for you:
Please be aware that the SRT6KXLT-5KTF requires a 208 volt 50 AMP dedicated circuit for your electrician to hard wire the input. There is an included step-down transformer to provide 120 to your devices. There is not a plug option for this UPS model as any UPS 6KVA or higher must be hardwired on the input.
Please let me know if you have any additional questions I can assist you with.
Patricia
You can take your load and runtime (runtime = how much time you will have on battery) requirements and filter down from there based on your other requirements (outlets, UPS topology, voltage, frequency, input cord, etc). You can use tools like our UPS selector or similar tools from other vendors if you want to take the DIY approach to UPS sizing. If you like the DIY approach and want to research further on your own, check out this UPS buying guide and this Top 12 Questions to Consider When Choosing UPS Systems for Network/Server Applications whitepaper too. We also have a total load calculator that can help with this process in many cases. Although in this case, on most of the calculators I have seen, the T430 is either listed at watts (which is the largest power supply for it) or not listed at all.
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Alternatively, you can bounce your requirements off of our application engineers & they can put together a few possible solutions for you to pick from (p.m. and I can set up an intro, or you can fill out the contact form here ). This is an easy & free way to offload some of the work and get expert input.
Diving into the specifics here, if you take the most conservative approach of sizing to the power supply, you are at watts (you probably won’t ever actually hit this number). As others have mentioned, a server will usually not draw the full capacity of the power supply. Some use the rule of thumb to multiply the power supply size by 0.7 to avoid oversizing (and over paying), or you can drill down and confirm the actual max power draw for the server. I’ll run with the conservative number of watts/750 watts per server here, but we can drill down and better quantify that number to make sure you don’t end up oversizing. At watts, you could likely get away with an efficient 5KVA UPS here, you’d be close to 100% load. For reference, I like to tell people to load the UPS between 60-80%, I think that strikes a good balance between actually utilizing the capacity you pay for, and leaving some “wiggle room” for new load to be added and upticks in usage. Given that, if you want to put everything on 1 UPS, you’d be looking at something like the SURT4UHV plus a PDU to give you the outlets you need.
Alternatively, you could go the route of splitting the load across smaller UPS systems. This would open the door to 120 volt UPS options, and theoretically eliminate single points of failure. For servers like this, I generally encourage people to go the online UPS route, but once you are in that lower capacity range, some lower cost line interactive units become feasible too.
You’d then need to answer the question: how much time do I need things to stay on when the lights go out? And add batteries if appropriate. For example, if we take the conservative approach to sizing the load ( watts, again I don’t think you’ll ever actually hit that number) and use the SURT4UHV, you’d have 3 minutes of run time with the included batteries, but could bump that up to 21 minutes by adding a BP192V12-3U . One of the nicer tools on our site are the runtime tables for a given UPS that let you see what adding batteries gets you at a given load. Here is the table for the SURT4UHV . What will probably drive how much you need to invest in batteries is: do you need the UPS to stay on just long enough for a generator to kick in or will you need it to support the load on its own for a while?
Side note: I’d encourage you to consider adding UPS backup on both of the power supplies if at all possible given your budget.
I hope this helps. A lot of the specifics will come down to what you have to work with as far as budget, electrical service, outlets, etc, so if you have the time to speak with an application engineer, ping me and I’ll get something set up. You might actually want to try this across a few vendors if this is your first time sizing a UPS.
@elibrody
When I did it, first step was recording the Amp spec on each device. Then add that up for a worse case scenario, all the while knowing that in real life it will likely be half that or less.
Next step is determining how long do I want to support those devices. Amps x hours equal Amp Hours. This tells you how many batteries you’ll want on hand.
By calculating using the worse case Amp numbers this helps compensate for how the batteries will diminish in their ability to keep things running over time. So you can meet your target time keeping things online over a multi-year period based on this method.
In the end the goal is to provide the backup window that you have determined is the minimum for whatever you need to accomplish during an extended power outage.
Lastly, review the manufacturer’s software and application (servers, VM host appliance, etc.) to be sure it can do the job in a simple, easy to configure way.
I have used CyberPower for well over 10 years and find their equipment and software to consistently meet this criteria I’ve set for keeping my rack protected from power issues.
Good luck with working out the details of your solution!
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