Plug a UPS into a UPS?

[Anonymous user]

We're considering a Symmetra to provide redundant (N+1) UPS power to various circuits throughout a building, with a generator and automatic transfer switch feeding the generator.

What if someone plugs a Back-UPS or Smart-UPS into one of the emergency circuits (Symmetra protected) instead of a regular circuit (no UPS/generator) accidentally? Just inefficient because of the AC-DC-AC-DC-AC conversion? Or is there something I'm not thinking of in terms of damaging or overloading equipment?

[TheNotoriousKMP_apc]

Hi,

You shouldn't have a problem plugging a smaller VA capacity Back-UPS & Smart-UPS downstream of a larger scale Symmetra. You're introducing a potential point of a failure, which frankly, isn't that high, but nonetheless still present.

[BillP]

Hi there, try this below link, its on APC's KB.

http://nam-en.apc.com/cgi-bin/nam_en.cfg/php/enduser/std_adp.php?p_faqid=397&tsk=b680w&pc=13134&keyc...

I found this information useful when I had the same question. Good luck....

Bala

[Anonymous user · Accepted solution]

You'll be fine.

However, if you connect any UPS downstream of a UPS that outputs modified square wave such as the BackUPS series, the downstream UPS will not accept the modified square wave as an acceptable power quality and won't switch to online operation and the device connected to the second UPS will not utilize the backup time of the upstream UPS.

If you use a standby sine wave UPS such as a SmartUPS, the downstream UPS will click during transition but you will be able to utilize the runtime of upstream UPS then when the upstream UPS is exhausted the downstream UPS will provide power.

With OnLine sine wave UPS like the Matrix, the downstream UPS will see it just like it's plugged into a utility outlet.