Recommendation for a UPS for my Mac and NAS?

Hi Don, racko,

Thanks. I went to the APC site and did various searches on their support boards. There was no clear-cut answer on the sine wave vs stepped sine wave (=modified square wave) question with regard to Macs. I even contacted the AppleCare support telephone line and none of the advisors could give a clear-cut answer. They suggested contacting the UPS manufacturer.

Apparently, Mac owners have used the APC Back-UPS models (stepped sine wave output) successfully, and the online Apple Store sells both Back-UPS and Smart-UPS models. One would think the Apple Store would not sell something that is inherently incompatible with their computers?

I guess one diagnostic factor is that if your Mac's power supply buzzes when the UPS is on battery, you may have an issue. That's not completely reassuring.

Servers may be more sensitive to the power they are getting, and it would certainly be worth making sure they get what they want. But, I'm not running a server.

So, I think it's still an open question.

Thanks,
Walter

Hi rackO,

I read through the white paper (thanks), and it does mention that standby-ferro UPS units are not compatible with PFC power supplies. I am familiar with the line conditioner units that used to be available that regulated voltage (and filtered) with a resonant transformer. Those were big, very heavy, and provided no backup battery. The UPS's available for the consumer are definitely not of that type. They are probably standby or line-interactive units, as the APC paper describes.

I chatted with an APC rep who recommended a Smart-UPS unit with sine wave output. He said that while Back-UPS units with stepped sine wave output will work, if a computer is run off it on battery for a prolonged time, it may result in a possible failure of the power supply. He did not specify what he meant by prolonged. I suspect that most people who are working at their computers when the power goes off and their UPS kicks in, are able to shut them down in a few minutes. Some computers have software to do a shutdown if the power goes off and they're on battery power. With a USB cable, the UPS can signal the computer of this condition.

He did not say that the Mac would NOT work with a Back-UPS unit. He simply cautioned that under extreme circumstances, a higher rate of failure may exist, if it's run off the battery for a long time. So, my question about whether Macs "require" sine wave output vs stepped sine wave output was not answered. As I read it, a Mac can use a stepped sine wave UPS, but there is a potential risk of power supply failure if it is used for a prolonged period on battery power.

This has bearing on those who want to live off the grid and use PVs and inverters to power AC equipment. That would likely fall into the "prolonged" use category, IMHO. You would not use a UPS in this situation anyway.

Basically, the owner must weigh the risks of using a unit like the Back-UPS, or paying quite a bit more for a Smart-UPS unit. I'm gonna have to think about this.

Thanks, rack0,

I was a little disappointed that I couldn't get a straight answer to my original question, but the APC guy came the closest to providing an answer. I had originally asked him about having stable power to finish a backup if the power went out. The reality is, if the power goes out, I should just cancel the Time Machine backup in progress, and shut down the system. I just wanted to avoid getting a corrupted backup and having to rebuild the backup from scratch. If the power goes out, finishing the backup isn't the main thing. I should just make sure to shut everything down gracefully.

Thanks