USP connected iMac doesn't power on after power outage

Discussion in 'iMac' started by Gio89, Aug 21, 2017.

  1. Gio89 macrumors newbie


    Jul 10, 2015
    Hello everybody,

    In my area there are frequent power outages. When the electricity is back my iMac won't turn on. It is connected to a UPS. The only solution I've found is to unplug it from the UPS, plug it into the main socket, switch the Mac on, switch it off and reconnect it to the UPS. This process is quite struggling since the UPS is hardly reachable and I have to repeat it a couple of times a week.
    The other devices connected to the UPS work fine after the outages. It seems the iMac adopts a kind of protection. Has this happened to you? Is there a way to avoid it?
  2. FreemanW macrumors 6502

    Sep 10, 2012
    The Real Northern California
    I suspect your UPS is not up to the power requirement of the iMac. THAT ought to be your focus.
  3. Gio89 thread starter macrumors newbie


    Jul 10, 2015
    Thanks for the reply.

    Better I clarify that the Mac doesn't shut down when an outage occurs, the UPS works well in that situation. The problem is when there's an outage with the Mac already off. In that case, when I try to switch it on, it doesn't.

    I'm not familiar with electrical stuff. Could you check if my UPS fits the iMac or not? It's an APC ES 700 (700VA, 320V) and a late 2015 27" iMac. I tried to disconnect all the plugs but the iMac one and do all the procedure again, the issue remains.
  4. old-wiz macrumors G3

    Mar 26, 2008
    West Suburban Boston Ma
    I suspect a problem with your UPS. I used about the same model UPS from APC with the extra connection from UPS to the Mac USB that tells the Mac to notify the user. The only problem I've had with the UPS is they don't last forever. My 2008 iMac has gone through 2 UPS deices since I bought it.
  5. hfg macrumors 68040


    Dec 1, 2006
    Cedar Rapids, IA. USA
    It is possible that the power-on surge of your iMac causes the UPS to shutdown as in an overload situation. When you power up the iMac directly from the mains, you recharge the capacitors in the power supply which then may result in a lower power-on surge which the UPS can handle easily.

    The fact that the iMac continues to run on UPS power after a power outage is normal, as it is probably at a low power-usage state while at idle or sleeping and is well within the steady-state capacity of the UPS.

    Personally, I would use at least a 1000va UPS with a fully loaded 27" iMac.
  6. nambuccaheadsau macrumors 68000


    Oct 19, 2007
    Nambucca Heads Australia
    And how old is it? Maybe time to change the battery in the UPS.

    Three to five years use is the most recommended maximum.
  7. USAntigoon macrumors regular


    Feb 13, 2008
    Rochester Hills, MI
    Try Systems>Energy Saver>Power-UPS... look into your UPS settings..If UPS is NOT connected to the iMac the UPS button will not show next to the Power button..
    May be these settings need to be looked at..
  8. cynics macrumors G4

    Jan 8, 2012
    Sounds like lock out state from the PSU, likely from over/under current/voltage during the transition from mains to battery or vice versa.

    PSU's can typically be reset by turning them off and back on. Since Mac's don't have a dedicated PSU switch they need to be unplugged and replugged back in.

    How old is the UPS? I would recommend a newer/better/bigger UPS regardless of age though.

    I have a APC NS 1080 that I picked up very cheap and while many will recommend a pure sinewave UPS mine has worked flawlessly. I just recommend doing some research and getting a high quality UPS since it sounds like you need it more then most of us.
  9. Gio89 thread starter macrumors newbie


    Jul 10, 2015
    Thanks guys.

    The UPS is less than 1 year old and I've had this issue since the first days. So the time-usage option has to be excluded, not a manufacturing defect though.

    No 'Power-UPS' option in my settings. The iMac is connected to the UPS exclusively through its power cable. These are the other connections – there's a reset button too.

    IMG_20170823_102007.jpg IMG_20170823_102049.jpg
  10. chrfr macrumors 604

    Jul 11, 2009
    The UPS would have included a cable that plugs into the "Data Port" on the UPS and has a USB connector on the other end. That is what gives your computer the signals that the UPS is on battery or on AC power.
  11. old-wiz macrumors G3

    Mar 26, 2008
    West Suburban Boston Ma
    Right - my UPS included the USB and OSx recognized it right away
  12. cynics macrumors G4

    Jan 8, 2012
    Like mentioned, there should be an RJ45 to USB cable connected to that data port to one of the USBs of the iMac. This lets the iMac know the battery state. That way you can get all the features from using a UPS.

    Screen Shot 2017-08-24 at 7.36.07 PM.png
    Screen Shot 2017-08-24 at 7.36.23 PM.png
    Screen Shot 2017-08-24 at 7.36.37 PM.png

    RJ45 to USB is probably a standard so generic cords should work if you don't have the original. However to be on the safe side APC part # is AP9827.

    Not sure if this will fix your problem or not though but its an important feature to use with a UPS.
  13. Gio89 thread starter macrumors newbie


    Jul 10, 2015
    I took me a while because I had to buy the data cable – I don't know where I tossed the original one.

    I bought this cable: APC 2 MT USB RJ50 Back-Ups CS500 Data Port AP9827 940-0127
    It should be like the original one. I connected it into 'data port' and directly into my Mac USB. Unfortunately it didn't solve the problem. When an outage occurs an info message pops up. The 'UPS' tab is not present in 'energy saver'.

    I also tried to push the 'circuit breaker' button after an outage. I did it after turning off the Mac and unplugging everything connected (except the data cable) for safety. When I reconnected everything the Mac turned on regularly. Normally, to make it turn on, I have to connect it to a simple socket outside the USP, turn it on and off, and then reconnect it into the USP. I imagine it is safe to press this button also when everything's connected, isn't it? I may use it as a temporary solution when an outage occurs. I still have to reach the USP under the table, but better then the entire procedure I mentioned above. o_O
  14. curmudgeonette macrumors 6502

    Jan 28, 2016
    Previously, were you not able to unplug from the UPS, wait a while, plug back into the UPS, and start up normally?

    A while back, a friend's old iMac was shutting down on its own (overheating? bad HDD?). To get it to turn on, we had to unplug from the wall, and plug back in. It seems that whatever initiated the shut down, remembered that it should be off, and refused to turn on. Losing all power by unplugging cleared that state.

    In your case, you Mac may be detecting unstable power, deciding it should shut down, but there's enough unstable power to keep it in the "shut down for safety" state.
    --- Post Merged, Sep 18, 2017 ---
    Perhaps your UPS isn't good at providing very low levels of power. Even when "off", the Mac will be drawing a tiny bit of power - sometimes called "vampire" power. The UPS will sense this power draw, but be unable to provide nice clean power. The Mac detects this and decides to force the "off" state for its safety.

    Try plugging an incandescent light into the UPS to see if the extra load improves the UPS's output such that the Mac doesn't see a problem.

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13 August 21, 2017