UPS plugged into a UPS

[BillP]

I have upgraded our server closet UPS system with RT class Smart-UPS and additional batteries to protect from power outages lasting an hour and to protect from a weird power problem we had where we got bad power that did not trip the UPS and damaged 2/3 of our servers three times over 2 months. It was a nightmare.

Each server used to have it's own UPS. Now I have just 2 for 5 servers plus a bunch of other stuff.  But now I find that I can't have my legacy Unix boxes do a network shutdown as they only support serial UPS comms. and I can't use both the serial and the NMC at the same time.

I can move them back to their own UPSes but then I loose the RT protection and the 1+ hour run time unless I spend another $4000 or so on 2 more RT Smart-UPSs and battery packs.

Or I could plug the small Back-UPS 1300s into the Smart-UPS 1500. The serial comms on the small ups will notify the Unix boxes via serial when the big one goes dead after the power has been out for an hour or so.

But if plugging a power strip into a power strip is a fire code violation, then a UPS into a UPS might also be a problem.

[BillP]

Well I did search this first. But when I put Daisy Chain into the search I got a lot of information. So my question has been answered.

Worse yet I found out that my power strip on my UPS is a no-no. When I have 8 small NAS devices each pulling just 30 watts or so there are not enough outlets on the UPS to get the job done. I will have to dig around to see.

Makes me regret ever moving to 1 large UPS. The 6 different UPSes I had before did not have this issue.

[BillP]

Hi Brian,

Often customers ask about daisy chaining UPS and surge strips and stuff like that thinking they'll get more UPS runtime or additional surge protection - which is not the case. I don't think it is UL listed either and maybe you already found that FAQ I know we have somewhere.

But, in general, connecting a power strip (or in the business/enterprise realm) a Rack PDU (Power Distribution Unit) AKA power strip is what you need to do to get outlets to support your actual load.

What I mean is that larger UPSs like Smart-UPS Online or even Symmetras typically have locking plugs on the rear - either 120V/208/240 type things like L5-30R or L6-30R. From there, yes, the idea is you plug in a power strip/Rack PDU, designed for equally distributing power, into the rear of the UPS and plug your load into that. Then, we have models where you can meter the power to each outlet, groups (banks) of outlets, control individual outlets or outlet groups, etc. 

In summary, I guess that with Back-UPS products, daisy chaining and connecting them to each other is frowned upon and could very well be a safety issue but for business class equipment, sometimes it is the requirement and recommendation to actually power your load. Of course, when you do this, you would be keeping in how much load the upstream circuit and UPS supports as to not add a ton of outlets with load attached that a circuit or UPS is not rated for..

I hope what I said is helpful. If you have any more questions, feel free to share.

[BillP · Accepted solution]

This was not about load or runtime. It was about keeping legacy and modern systems working together with the best protection.

I am having the unix admin look into network communications on the legacy equipment. If it can't do it, then I will ask management if I can force the issue of virtualization or buy dedicated UPSes for the unix boxes of appropriate capabilities.

Thanks for your time.

Brian