I believe I may know (at least part of) the answer here. Bear with me...

Others have stated in this thread that Dell is likely rebranding an APC 
product. While I have not looked into this specifically, I would be highly 
inclined to believe this to be the case. Dell doesn't make printers, switches, 
mice, or keyboards, so why should they make UPSes?

I digress.

While it sounds like a sales tactic, you should always ask why. It is possible 
that there is an ounce of truth to what he is saying, but he may not know why. 
Regardless, I would be willing to bet that a selection of the correct UPS from 
just about any major vendor, particularly APC, would work just fine. He's 
likely pushing that sales pitch, 1) because it is Dell branded, but 2) because 
the UPS is known to work properly with the power supplies employed in that 
particular line of servers (specifically, Power Factor Correction power 
supplies).

There actually are many differences between UPS types and how they behave, both 
while utility power is present and when utility power is removed. There are 
UPSes that switch from utility to battery backup, causing a slight interruption 
in power for a few milliseconds. This is tolerable for most consumer 
electronics and even PCs and servers, as long as the end user device power 
supply maintains a capacitive charge long enough to power the device for the 
duration of the transfer from utility to battery. This type of UPS is referred 
to as an Offline or Standby type, and is likely what you have at your desk, if 
you have one.

Additionally, there are UPSes that actually never break the connection to the 
end user device, and so there is zero transfer time that is realized on the 
output. These UPSes are typically more expensive than what most of us buy on a 
regular basis, unless we've got some really big and critical loads that we're 
protecting. These are referred to as Online, or possibly Ferro Resonant, or 
Double Conversion UPSes, depending on the technology & design.

Finally, (and this is where the ounce of truth comes in) there are also 
differences in how the power output is generated by the UPS. This is likely 
what the sales person was referring to in the sales pitch (aside from the fact 
that he was pushing a particular brand). There are sine wave, simulated sine 
wave, and various square wave outputs depending on the quality and technologies 
employed in the UPS design. As I mentioned earlier, Power Factor Correction 
power supplies do NOT like a square wave power source - they are designed for a 
true sine wave power source and will not run properly, if at all, from a square 
wave power source. Low end UPSes tend to have a modified square wave or a 
stepped square wave instead of what would be seen as a more pure sine wave 
output. Total Harmonic Distortion also plays a key role here. So, if the power 
supply of the device cannot run well on a simulated or stepped square wave 
power, and the UPS is an offline type that generates a stepped square wave when 
the utility is lost, then all you really have is an extra heavy surge 
suppressor...everything is fine when online, but the instant you lose utility 
power, your load device will likely lose power as well.

For more information, see these links:

http://en.wikipedia.org/wiki/Uninterruptible_power_supply

http://en.wikipedia.org/wiki/Inverter_(electrical) (specifically scroll down to 
"Output waveforms"

http://www.cyberpowersystems.com/support/faqs/topologysinewave.html (good read 
in general talking about UPS and Output Waveform types.)

http://en.wikipedia.org/wiki/Power_factor#Passive_PFC (Power Factor Correction)


Jonathan L. Raper, A+, MCSA, MCSE
Technology Coordinator
Eagle Physicians & Associates, PA
[email protected]<BLOCKED::mailto:%[email protected]>
www.eaglemds.com<BLOCKED::http://www.eaglemds.com/>

________________________________
From: Laurence Childs [mailto:[email protected]]
Sent: Wednesday, January 12, 2011 8:04 AM
To: NT System Admin Issues
Subject: DELL UPS

Hi All

I'm in the process of sourcing a new server and UPS for a client

Currently looking to choose between DELL & HP, however my supplier is saying 
that I should use DELL UPS with the DELL server as other UPS i.e. APC 'don't 
always work'

Has anybody heard of or experienced this?

Cheers

Laurence

~ Finally, powerful endpoint security that ISN'T a resource hog! ~
~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/>  ~

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