APC UPS for iMac

I would hesitate to use anything other than a true sine wave UPS. The less expensive ones make a square wave and it either over amps or under voltages your system.

I have an APC ES 550 and it works fine with a mid 2010 27" iMac i7.

I have the same APC model as you, it works fine on a 2011 iMac.

You won't regret it, and thanks.

Hi I have some weird problem related to this and unfortunately either or apple or APS able to solve.

I have picked a 27 iMac late 2012 model 2 montsh back and a APC Back up UPS 700.

Whenevr I turn on the Main power> Turn on APC> Turn on iMac, the iMac doesn't turn on. I will have to unplug it and plug it back it works. It happens only when I start the UPS for the first time in the day. After that how many ever times I remove my iMac plug and plug it back to APC, it turns on.

Initially I thought, it is the problem with the UPS and contacted APC where they replaced with a new UPS and its the same problem.

Unfortunately, Apple is not able to tell that its the problem with the Apple iMac as it works fine when directly powered without using APC.

So, the problem lies working with APC and iMac together.

Could someone please help. The last option I have is to carry the UPS to a Apple store and see if it works fine with any other iMac.

Also to mention, I did try SMC reset adn PRAM reset.

Hi I have exactly the same problem. Did you solve it?

I do not quite understand why someone would turn off the power to the APC or the main power for that matter - I leave that plugged in 24/7 and simply either shut down the Mac or let it sleep. No problem with that. Unplugging the main power to the Mac will simply wear out the small internal battery much faster which keeps the clock and settings going.

Hi babowa. Let me explain. With the APC UPS attached if the power goes out the imac simply swithces off!. (it's as if there is no UpS attached) Mac OS 10.8.5 reports that the UPS is attached and working, but it simply doesn't. I have an old MacPro which work fine. It appears to be a problem with my iMac. However I can't beleive that it's affecting all iMac. Maybe someone on here has the answer

How do you have your Energy Saver preferences (in System Preferences) for the APC set? You can control the behavior there. You can usually indicate when the Mac should shut off and it is usually a few minutes as you cannot expect the battery of the UPS to last very long; they're designed to give you time to close out your apps and shut down the Mac safely.

This has nothing to do with that. It's as if there is no UPS connected. At the slightest hint of a power failure the mac simply switches off. Unlike my MacPro which behaves properly using anidentical UPS with the same settings. The problem seeems to be related to the iMac in some way eith the type of power supply or the OS 10.8.5. Any thoughts?

The APC may not provide a good enough sine wave for the iMac's liking; inexpemsive UPSs tend to produce more of a square wave compared to the sine wave AC that the power supply expects.

You may need a "pure sine wave" UPS; the typical symptom is that if your power supply doesn't like the UPS's output, it will just shut off.

Here's an image that shows the issue:

The black sine wave is the AC your power supply normally sees at the wall; cheaper UPSs generate an approximation as shown by the red line, and many power supplies don't like that.

I don't know which APC Back UPS 700 you have, but for example the speacs for the Back-UPS LS 700 states "Output Waveform: Stepped approximation to Sinewave."