I would like to start a new forum both for discussion and as a warning to members to remember “caveat emptor”.

Recently I was asked about a UPS and their ratings, a fellow small business that normally looks after its own computers. This led me to have a quick look at some sites of UPS suppliers and I was intrigued. I can understand that we are in a marketplace and that each will specify in a way that sets them apart. Most suggest not unreasonably that if you have any doubts contact them or use their product selectors.
The problem I came across was a business acquaintance was given poor advice. They had not made it clear that their 350VA UPS was average power rather than peak power now to me that is codswallop. We all know that UPS equipment has several functions being better surge protection, voltage regulation (to reduce stress on the internal PS) and lastly but most importantly that ability to continue operation after power fails for a period even if it is only for an orderly shutdown. Therefore we would expect that any rating would be based on a fully fired up computer working flat out as it shuts down. During shutdown the CPU, memory and HDD are all working hard as data is written to disk prior to shutdown hence average is a useless specification.

If it was for a longer period the average power may become appropriate but for a rating that only has to last a minimum of 3 minutes for an immediate shutdown 5-10 minute maximum, an average rating is !@#$%^&*. This is reminiscent of the move many moons ago in audio amplifiers from RMS to peak, to peak effective ratings. The reality was no change in mean power usage but the highs went higher and while it could reach these high peaks they could not handle sustained high peaks with a consequence of lost fidelity it was mostly all about marketing and this is the same story.

We all understand that most computers do not draw the full power of their supply but in this case the draw without monitor was about 200VA maximum power draw on a P4 measured with a Fluke power meter. The supply immediately shutdown in a brownout it would not hold up even then why because the 350VA was really about 175VA peak. Totally inappropriate to the functionality sought and PAID for.

We should be able to say a PSU is rated at x plus the rating of any other equipment attached to arrive at a number. By way of example a 350W PSU and a 150VA monitor (CRT type) to arrive at a total of 500W. It would be nice that you could assume that a 500VA would cover the system for a minimum of 3 minutes with no fudge actor to multiply by. We could then assume that the 350W PSU would not be fully utilised since it would most likely die before a power failure this builds in a safety factor. This would automatically compensate for any power factor losses and extend the time beyond the minimum required. You may then choose to reduce your operating margin as an informed customer not one sitting under a mushroom being fed !@#$%^&*

Ok manufacturers can have their marketing blurb but have some realistic technical literature available that reflects common terminology rather than marketing weasel words. Peak and average have reasonably well understood meanings and technical literature should indicate if nothing else a duty cycle if it is not peak power draw for the minimum period required. The manufacturer to be fair replaced the 350VA unit with a 800VA unit. So the 350VA unit is only good for very light loading such as notebooks and small peripherals. My comments apply to only one brand and I would like to hear other members comments to see if it is just one manufacturer or a growing trend of marketing crap from the industry at large.