Proper UPS for a Server Rack with a Generator

[tpoole]

Hello,

We have a server rack at our office and currently I have four APC Smart-UPS 1000's. I can set the voltage sensitivity on low and they work fine when we lose power and our generator is running. 

However, are we buying the wrong units? Should we be buying the units that have "double-conversion"?

Thanks

[Teken]

Generally speaking any new hardware under consideration should be reviewed based on its specifications and the environment it’s intended to operate in. 

Once the list has been narrowed down several units should be put in place for short term evaluation & testing in the actual live environment it’s intended to be operating in.

If finances are not an issue double conversion systems offer the cleanest and regulated power output of all UPS topologies vs Line Interactive.

You’ll definitely want to validate how each system performs while on Generator power! ☝️ As you may find some model UPS do not go back (On-Line) once the generator power is fully running! 🤦‍♂️

Meaning, the UPS System will remain on (Battery Only) mode until such time grid power is restored. In this specific instance the batteries inside the unit will be depleted and thus initiate a shutdown of the connected loads. ☹️

Don’t assume the UPS only needs to run on battery mode for a short period of time because reality rarely if ever matches expectations!

The bottom line is to match the UPS System to the generator on site. As you’re not going to replace the building generator! 🤣

[tpoole]

Finances are not an issue in this situation :). I want the rack to be as reliable as it can. The APC UPS' we buy, will only work if the power quality is set to low when our generator is running. So I just want to make sure we have what is best. 

[Teken]

Based on your reply that the power quality must be set to low reinforces the need to trial a demo unit on site before committing to a larger purchase.

The buildings power generator is obviously old and outputting dirty power. More often than not it’s due to lack of serious maintenance and calibration to insure a stable output voltage and frequency.

Besides the two it’s always going to be out of band THD! 

[tpoole]

Well from my understanding the double conversion is the way to address these issues correct? 

The generator is 6-7 years old but we do have it serviced one per year. 

[Teken]

A double conversion vs line Interactive topology has nothing to do with whether the hardware will operate as you expect when the building is on generator power.

The only difference is a double conversion system provides constant regulated pure sine wave output to the attached loads.

It has no baring on how the UPS will react when the AC Mains power supply is out of band / sees dirty power! ☝️

You can review the APC FAQ as it relates to generators: 

https://www.apc.com/us/en/faqs/FA158891/

You can also search in this APC Forum and the internet as to how many people / companies have problems with UPS while on generator power only. 

This problem is not unique to APC and affects every other UPS manufacturer on the market.

As you noted early on in your first post. The old system had to be adjusted to low power quality setting. This simply means the hardware was defined to accept a wider input voltage, frequency, THD.

In plain English, dirty power . . .  🤢

Generally speaking the vast majority of electronic hardware is designed for multi voltage / multi frequency. As such they by default are capable of accepting the perceived dirty power without issues. 👍

Everything else that isn’t designed with a wide operating range simply heat up or begin to operate erratically until it fails.

Bottom line, request a demo unit for short term trials. You’ll quickly see the results are some units require absolutely no changes in the power quality setting vs others do.