I've 2 power sources in my house: One from the national power grid and another from an internal power source. I've several power sockets in my server room from these 2 sources.

Did some research and I was unable to find a UPS systems (at a reasonable cost) that use power from source 1 and, in case of failure, it would switch to source 2 until source 1 becomes available.

I was able to find expensive solutions for the entire home power grid but is there any reasonable priced consumers UPS that adds redundancy with a second power input? Like having a second input socket plug.

Note: For my user case, none of the servers contains redundant power supplies.

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  • I think the redundant power selector and the UPS should be different parts. So you can use a cheap UPS and a cheap power switcher. | The thing surely exists, I've already seen a simple Linux/PC server which had multiple power inputs AND an internal UPS (built into its power supply). – peterh - Reinstate Monica Aug 15 '17 at 3:48

You're looking for a power distribution unit (PDU) with an automatic transfer switch (ATS). The PDU can choose a power source from two (or more) sources to use -- in this case, it would use one with power if one of the sources goes out -- and switch seamless between the two. I think all such PDUs handle power phases so you don't have to worry about circuit phases. You would hook up the PDU to two different UPSes (or just one, especially if that one is hooked up to a generator that has a bit of start up time), each hooked up to a different circuit.

A PDU with ATS is also useful for testing your UPSes since you can just unplug one from the wall and see if it kicks in.

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  • This is the most correct answer by far, a UPS is not really what the the OP is looking for. – quadruplebucky Sep 1 '17 at 19:01

The reason there probably isn't such thing as an UPS with two power sources is that such UPS would be a single point of failure.

Instead, most servers are capable of having two power supplies. Even with just one power source it's wise to have separate UPS for each power supply. And if (& as) this is not about servers in a business environment, it's off-topic on Serverfault.

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  • UPSs come in all different sizes. Fairbanks AK has one that can sustain it during outages, and they can exist on either side of a PDU (and usually do in modern datacenters) – quadruplebucky Sep 1 '17 at 18:57
  • Good to know. Still, I prefer having separate power source, UPS and power supply to prevent a single point of failure. How this is prevented in their solution? – Esa Jokinen Sep 1 '17 at 18:59

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