UPS and surge protector info, tips and tidbits.

[qxp]

This is meant to be a dedicated thread for discussion of UPS and surge protectors.

• Models which worked fine for you over the years ?
• Models that should be avoided ?
• UPS and surge protector electronics
• UPS battery chemistry (do you prefer lead sulfur or lithium or something else ?)
• UPS type preference - always online, AVR, something else.

There are different kinds of UPS.

• The simplest has a battery and normally just passes current through. If out of tolerance voltage is detected the UPS switches to draw power from the battery. The problem is at which point should it switch? Line voltage fluctuates from changing loads so having tight tolerance means it switches often and having loose tolerance means the output voltage can have big swings.
• The more complicated one has an internal transformer with several windings that let you step up or step down input voltage by 10-20%. Then the UPS first switches the transformer windings before using the battery. This is called "automatic voltage regulation" or something similar. These marketing terms might change with time so check how your UPS works.
• An "always online" UPS always converts input voltage (if any) to internal DC voltage, while the output is provided by DC-AC converter that always works. When input voltage is absent or too small the internal DC bus is powered by battery. This UPS provides rock steady output. It is also not necessary for such a UPS to switch, though often there would be a relay to disconnect the input.

The downsides to the UPSes that switch is that they typically use electromagnetic relays that have a limited lifespan - on the order of 10000-20000 switches. Not a problem if everything works well. Potential problem if electronics malfunctions or tolerances are too tight and it switch every few seconds.

The downside to always online UPSes is that there is efficiency loss when converting to DC and then back to AC. Depending on construction the output converter could have a limited lifespan due to capacitors for example - if anyone has info on that please post.

 

[Bill_Bright]

This has been discussed ad nauseum on this site. I don't see it becoming more than heated debate between those who are already set in their ways.

That said, I will give my three cents.

1. Models over the years? Every couple years makers come out with new models (or at least new model numbers) so not sure that information will be of use. For example, I have an APC Smart UPS 900 that is over 30 years old and still working just fine - but definitely not still in production. Most my UPS here are at least 7 years old.

2. "Models to avoid" is the same thing. I will just say, "cheap models" should be avoided - just as cheap PSUs should be avoided. And of course, underpowered models should be avoided.

3. Not a question. But a surge and spike protectors are little more than fancy and expensive extension cords as they do nothing for low voltage events like dips (opposite of spikes), sags (opposite of surges) or brownouts (long duration sags). They don't regulate the power. They "clamp" (chop off) the peaks of surges and spikes. And for excessive surges and spikes, they simply cut power (“IF” working properly), crashing your computer - never good. A "good" UPS with AVR "regulates" the voltage, attenuating when high and boosting when low (even without kicking over to battery, except for extreme anomalies) - that is a huge and most significant difference.

4. I prefer SLA (sealed lead acid) simply because they are affordable, very capable, and easy to find and for the most part, the most common are universal (not proprietary. Plus somewhere around 95% of a SLA battery can be recycled. No other battery type comes close to that.

5. Always on-line are too expensive and not needed (except in very rare, "mission critical" or medical "life support" scenarios) for computer and SOHO networks. A "good" UPS with AVR is plenty quick to react to power anomalies with time to spare. AVR is essential and the primary reason to have an UPS. Battery backup during a full power outage is just a minor bonus feature.

Do not fall for the marketing hogwash hype that today's computers need pure sinewave waveform output UPS. They don't. Stepped approximated, simulated, modified, or whatever you want to call it is just fine. Folks must remember that 99.9% of the time, the UPS is passing through the same (or perhaps slightly regulated, if needed) waveform from the wall outlet. Only when providing battery backup power during a full outage does the UPS provide UPS generated waveforms.

That said, the price for pure sinewave UPS have come down significantly in recent years to make them competitive. So if you find a "good" UPS with AVR that outputs pure sinewave waveforms when on battery at a good price, and it has all the features you want, go for it. Just do NOT dismiss a good UPS with AVR that other wise meets your power and feature needs just because it outputs a modified wave form.