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PFC power supply on new 27" iMac?

1100 Views 10 Replies Latest reply: Feb 27, 2013 11:36 AM by Paul Elson RSS
Paul Elson Level 1 Level 1 (25 points)
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Feb 23, 2013 3:23 PM

Are UPS' that provide pure sine wave battery backup power necessary for the new iMacs; i.e., CyberPower UPS'?

 

UPS' from APC have this, but only in the Smart models which are much more expensive.  Excellent Amazon reviews for both units.

  • OrangeMarlin Level 5 Level 5 (5,130 points)
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    Feb 23, 2013 3:30 PM (in response to Paul Elson)

    I just purchased the CyberPower UPS, connected it via USB to my iMac, and it seems to be working fine. Don't know about the APC, but you're right, feature to feature comparison, lead me to purchase the CyberPower.

     

    By the way, the iMac automatically reads the model number and specifications, and allowed me to set up things like to shut down my iMac when the power goes out, which is great. We have rolling blackouts around here during the summer.

  • OrangeMarlin Level 5 Level 5 (5,130 points)
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    Feb 23, 2013 6:07 PM (in response to Paul Elson)

    A 27" iMac that's awake and screen on, draws about 300 watts, so a quick back of the napkin calculation would run three hours on your UPS. Throw in the second monitor, router, drives, and what 2hours? Or am I calculating that wrong.

  • OrangeMarlin Level 5 Level 5 (5,130 points)
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    Feb 24, 2013 12:03 PM (in response to Paul Elson)

    The good thing about Mac's Energy Saver preference panel and the CyberPower UPS is that you can set it up to self shut down if the power goes off. I leave my iMac on 24/7, so I might be out of my house when the power goes off, or just taking a shower. I think you're overlooking how useful it can be when you're not there.

     

    A 42" plasma draws 200-300 watts also.  You might be cutting it close.

     

    Also, do you realize that a pure sine wave UPS is probably not that important, unless your intent is to run for a long period of time without power from the Grid.

     

    1. All Macs have an Active Power Factor Correction power supply (called PFC), which allows them to be used with a wide range of voltage and electrical quality. I believe this was implemented in 2007
    2. UPS manufacturers want you to believe that pure sine wave models (more expensive) are necessary for PFC computers. BUT, that's only if you're running for a long period of time (say a server). You have already said you intend to shut down your computer (or as I recommend, set up for auto-shutdown), so we're talking just a few minutes.
    3. A well designed UPS (which we're discussing, not some off brand piece of junk), the UPS should be able to transfer from external power to battery in a few milliseconds. Mine has the spec of 8 milliseconds. Here's where the problem occurs and where you might have an issue. If you do not have enough "headroom" on your UPS to handle all the wattage being drawn, even a pure sinewave UPS will cause a dropped power load.

     

    So if your intent is just short-term, and if you want to add that plasma, my suggestion is you don't spend money on a pure sine wave UPS, and up the rated wattage of your UPS to handle that instanteous surge where the APC may draw a full load at the moment of switchover.

     

    I went with a non-sinewave (but a simulated one) with 600 watts which is huge overhead to my 300 watt iMac (at it's highest draw), and a small 15 watt draw of an external Time Machine drive.

     

    I tested my system by shutting off the relay to my home office, and I got about 10 minutes of power for both (but the screen was on the iMac, which might be different if it were in display sleep mode). The battery worked flawlessly, though I probably wish I had gone with a 1000 watt version, just in case the shutdown takes a long time.

     

    Don't overpay for what you don't need. If you want to protect all of the devices you want, spend on reserve power, not on a pure sine wave.

  • OrangeMarlin Level 5 Level 5 (5,130 points)
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    Feb 26, 2013 9:56 PM (in response to Paul Elson)

    Sorry I missed this.

     

    Yes, I have a surge suppressor between the UPS and the wall, but it's probably overkill from looking at the specs of the Cyberpower. But I don't live in an area of the USA where power surges are common (I haven't heard a thunderstorm in 2 years).

     

    I have used Time Machine from nearly the moment it was launched. I am using OSX 10.8.2 and the most recent iMac built. I have had not one single problem. In fact, I have found TM new and improved over previous versions. For example, when I set up my new iMac, I restored from my TM backup from my recently replaced MacBook Pro. Usually, at this point,  you have to erase your Time Machine and start over. But now, it just carries on with the backups, saving all the ones from the MBP. It was beautiful.

     

    I'll have to find that thread and comment.

  • OrangeMarlin Level 5 Level 5 (5,130 points)
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    Feb 27, 2013 8:57 AM (in response to Paul Elson)

    I'm a solid believer in Time Machine and I do everything I can to protect my data. After a Time Machine HDD crashed a few years ago (and having its replacement die), I avoid one brand of external drive. But because I'm OCD about all of this, I now back up the Time Machine.

     

    What I do is I clone it (there are a bunch of good Mac cloning programs for little or no cost) about once ever 2-3 weeks. Then I store the clone in a fireproof lockbox away from home. So if my Mac gets stolen, I've still got a backup.

     

    I'll take a look at that thread. Maybe I can help.

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