[LordOpie]

If you've got a closet full of electronics (eg. server) and you've got two battery backups... if you plug one into a backup port, does that make the surge only ports on that one also backup?

I mean, yes, I know it should, but is there a reason why I shouldn't? Would it consistently create too much of a draw that it would short out the first one?

 

[binary visions]

I'm not an electrical engineer but I'm told that this (plugging a UPS into another UPS) is a definite no-no. I've heard a couple different explanations, the one that I remember most clearly was that a UPS does not output a pure sine-wave current and thus can either cook a primitive UPS or simply cause a more advanced UPS to shut down to protect itself.

Again, I'm not sure if that's a correct explanation but I've certainly heard enough people tell me not to do this, that I wouldn't try it on expensive equipment or expensive battery backups.

A Google hit:
http://www.powerware.com/FAQManager/afmviewfaq.asp?faqid=8

 

[johnbryanpeters]

It depends on the UPS being plugged into. For many reasons, not a good idea. It can damage one or both UPSs.

 

[LordOpie]

Thanks!

Seems like without the proper sophisticated filters, it's tantamount to making a photocopy from a copy instead of the original... like the movie Multiplicity... "I'm spitting on bugs Steve."

 

[johnbryanpeters]

The actual issue is that if the output waveform of the first UPS is not pretty close to a sine, high frequency harmonics will cause the surge suppression of the second UPS or suppressor to activate, which can
a) Overload the first UPS.
b) Overheat the surge suppressors.
Things can get ugly quick.

 

[binary visions]

Thanks, JBP. Appreciate the explanation. A high quality UPS should shut itself down before cooking, but it definitely sounds like a bad practice unless you're sure of your equipment.

Will a higher quality UPS provide a better output for a second UPS? Or is the lack of a current being a sine something inherent in all of the UPS devices?

 

[DRB]

I'm thinking it would be dead bang funny if we sent a couple to MMike.

 

[LordOpie]

Will a higher quality UPS provide a better output for a second UPS? Or is the lack of a current being a sine something inherent in all of the UPS devices?

It's all about the internal filters. Higher quality/expense UPS's have the filters.

I vaguely remember my electrical engineering courses all those years back about converting wave patterns and stuff

 

[splat]

also the other issue with Plugging one ups into another is that the draw of a UPS is much larger than its output , so you can easily over load the one UPS.

think about it , when you plug it in the wall , it runs all the equpipment and Charges the batteries at the same time. very high draw.