Hey all,
Building out my lab, I was going to get a rackmount UPS. The one I’m looking at is a Cyberpower OR1500LCDRM1U. It says it offers:
1500 VA, 900 W, 120 V
Do I understand correctly that all I need to do is find the Wattage rating for each of the components I want to plug in and add them up? My components right now are pretty light, only about 120 watts total. But soon I’m going to expand and build out a Nutanix CE cluster with 3 nodes and a rack of drives. I was looking at using some NUCs but they are each rated at 330W.
So that would mean even the NUCs by themselves would over-provision the UPS right? Then on top of that I would still need all the other equipment in the rack to be powered.
Am I understanding this correctly or is there something I’m missing?
The thing you’re missing is runtime. If you match your usage to the UPS exactly, your runtime will be zero. If you consume 300W, your UPS needs to provide 300W for however long it is until the power is back. All major UPS companies (APC, Eaton, Cyberpower) have calculators on their site.
But a UPS for extended runtime will be very expensive, and lead-acid batteries must be replaced every five years or less, else they will not be able to sustain a load, so budget for that maintenance too.
A UPS is really just to bridge the gap between mains power going out and a generator coming online. A large-capacity UPS will be prohibitively expensive.
Also, note that cited power figures on the NUCs are probably peak draw. They will probably draw less on regular usage; you’d have to measure it to know for sure in your specific use case.
They’re also useful to be able to gracefully shutdown your systems in the event of an outage. Mine has a desktop app that’ll do it for you.
My Cyberpower UPS started going to shit last year and I ended up replacing it with a LiFePO4 power station that advertised a switching time fast enough to use as a UPS. I spent about $630 for a power station that can handle 1800W for an appreciably longer runtime than the lead acid battery backups, essentially one kilowatt hour. So far so good. My only complaint is that the outlets are on the front, which isn’t an ideal form factor for UPS duty. Plus, LiFePO4 is supposed to be good for ten years or so.
What did you choose?
Ecoflow DELTA 3 Plus
Watts is peak usage not watt hours. You can have two 1500 watt UPSs but one could last far longer because it has extra batteries but the same 1500 watt inverter as another model.
Right, but also UPSes are usually rated in VA, not W.
So the UPS I was looking at is here: https://www.microcenter.com/product/506629/apc-smart-connect-ups-(smc1500-2uc)
It lists VA, W, and V.
You have to look at the datasheet. It says 6 minutes at full load and 18 minutes at half. Full data can’t be listed because it’s a non linear curve. The website gives you a calculator at the bottom.
You pay a huge premium for rack mount. You could buy 2-3 regular UPS for the price of one rack mount. I bought a shelf for my rack and have regular UPSs on the shelf. Note that you can only chain 1 ups into another without problems. So it’s best to separate devices onto different UPSs or buy one that supports plugging external batteries.
if you match your usage to the UPS exactly, your runtime will be zero
No, it will be 1 exactly.
But what is the unit of 1? Minutes? Seconds, Hours? That’s what’s missing in the OP
Other have answered the runtime and load question very well already.
I have three other points.
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Batteries degrade over time. Over-speccing your UPS means more likelyhood that things will hold up in three years time as the capacity given is for new ones. Plus, not running your UPS at 100% capacity reduces its stress. Again, more reliable.
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You can get a much better quality UPS by buying a second hand one without batteries off ebay and replacing them yourself, typically for a fraction of the cost of buying new. Plus you know you have new batteries. UPS is something where quality genuinely matters. I’ve had to carry a cheap and badly made UPS out of an office whilst it was on fire, so now I spec more carefully. (And ensure they’re metal bodied!)
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Consider what you NEED to power. What sort of power cuts are you expecting? Does it matter if something goes down?
I UPS my servers and my main desktop, but not my routers, nor my wifi or IOT things. My internet provider also goes out when there’s a cut (I’m on a mesh system so rely on neighbours, who will typically also be down) and I can’t do much without power anyway, but it keeps the disks spinning. We typically get very short automated outages here of less than 10s (yesterday was a bad day, we had 9 within 2 hours)
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