First let me make sure it's clear that I am NOT trying to extend runtime by connecting two UPSs in series. That's been asked a million times on various forums, and is not what I'm trying to accomplish.
I've had 3 UPS units fail on me in the last 12-18 months, and I'm starting to wonder if it's the power flickers that are doing them in. My power rarely goes out for more than a minute or five, but before it does, it always violently flickers for a few seconds. Those flickers are hell on my unprotected equipment, and I'm wondering if that's what has caused my UPSs to die prematurely (the newest one barely lasted 5 months).
The old ones still function and still seem to do automatic voltage regulation, but none of them last more than 1-2 seconds once they switch to battery. I've tested the batteries, and they're fine; they were also all replaced about 9 months ago.
So, what I'm hoping is that the old ones can sit upstream of the new UPSs to take the brunt of any rapid brownout /surges and keep my new UPSs healthy. They're all pure sine wave and similarly rated.
Thoughts? Warnings/cautions?
Both Eaton and APC advice against daisy chaining, claiming it would cause extraneous strain to the first UPS in the chain, possibly overloading it.
Yeah, I read similar. And as general advice, that's probably solid.
In my case, both old and new are the same rating and I limit the loads to half of what they're rated for (which is why I have 3 UPSs instead of 2). So overloading them isn't high on my concern list. Was mostly just looking out for any kind of hidden gotchas.
The only issue I've thought of is at least one of my old ones no longer automatically kicks back on when power is restored. That would be a bit of a deal breaker.
Basically I just want to use them as power conditioners since they have AVR and surge protection on the battery output versus just surge protection on the "surge only" outlets.