UPS and power strip interactions?

Sometimes I hear that you shouldn't plug (UPS brand X / any UPS) into (power strip brand X / any power strip) because of some interaction leading to poorly conditioned power, reduced battery life, massive explosions spattering the room with battery acid, and so on. Sometimes I hear that it's the power strip that you shouldn't plug into the UPS. What I haven't gotten is a clear idea of how reliable these recommendations are or how generally/specifically they apply.

Can anyone speak precisely and non-urban-legendfully on these UPS and power strip interactions, if there are in fact ones worth thinking about?

Solution 1:

Having had some 'discussions' with the inspector that comes around our offices once a year to make sure we're not being bad, I have a better idea as to what code says about this. Paraphrased from said inspector:

• Thou shalt not plug a power-strip into another power-strip Nor any multi-outlet device into another multi-outlet device, for it is a fire-hazard, and therefore bad.
• Thy UPS counts as a multi-outlet device Therefore thou shalt not plug thy UPS into thy power strip, nor plug thy power-strip into thy UPS, for it is a fire-hazard, and therefore bad.
• A multi-outlet device shall only be permitted to be attached to another multi-outlet device if it is hard-wired into the first multi-outlet device Which renders it a single multi-outlet device.

The inspector wasn't kind enough to elucidate what, exactly, constitutes the 'fire-hazard'. We get dinged on the power-strip in power-strip commandment every other year or so. This necessitated the purchase of a bunch of long-tail power-strips (power strips on a 15' cord), and a few long extension cords with 3 outlets on the ends of them.

Edit: Regarding rackmount UPS's and PDU's. I believe they're OK so long as the PDU plugs into a locking outlet of some kind, such as an L5-20 or L5-30.

Solution 2:

I have seen some very, very bad server interactions when you plug a UPS into another UPS, and run a server off it.

In our specific case, the server had a clock that ran ridiculously fast, as in, it would gain 5+ secs per hour. Removing the "double UPS" fixed this.

Granted this is not exactly what you're describing, but I would say based on my experience that nothing should be run "upstream" of any quality UPS. Plugging a power strip in "downstream" of the UPS may not be up to fire code (per @sysadmin1138 excellent response) but it's probably not going to hurt anything.