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.
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.
https://www.eaton.com/us/en-us/products/backup-power-ups-surge-it-power-distribution/backup-power-ups/va-versus-watts--eaton.html
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.
https://www.apc.com/us/en/product/SMC1500-2UC/apc-smartups-c-line-interactive-1440va-rackmount-2u-120v-6x-nema-515r-outlets-smartconnect-port-usb-and-serial-communication-avrgraphic-lcd/
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.