Resolved Quick Question: Power Outages in sleeping iMac

Discussion in 'iMac' started by gabrielsanz, May 9, 2016.

  1. gabrielsanz macrumors newbie


    Jan 31, 2016
    I usually leave my iMac in sleep mode at night and lately there have been some blackouts in my neighborhood that have me a bit worried.

    Will power outages cause any damage besides the loss of unsaved files when it's in sleep mode?


    P.S. I know I need a UPS.
  2. maflynn Moderator


    Staff Member

    May 3, 2009
    Possibly, if there are spikes just before or after the outage, that may damage the computer. Make sure you have a surge protector, and/or just unplug it at night to be safe.
  3. Gav2k macrumors G3


    Jul 24, 2009
    If your Mac has been asleep long enough you'll lose no data. The issue is the surge of power as it goes off or comes back on that could damage your Mac.
  4. gabrielsanz thread starter macrumors newbie


    Jan 31, 2016
    Alright, I'm buying that USP+surge protector ASAP. Thank you!
  5. rigormortis, May 9, 2016
    Last edited: May 9, 2016

    rigormortis macrumors 68000


    Jun 11, 2009
    when i first bought my haswell mac mini, it would sustain a complete power outage for 30 to 45 seconds with zero power in sleep mode. my ups was failing and it dropped the load hard. and i noticed the power light still flashing.

    i wrote it off to the residual energy of the capacitors keeping the ram contents alive and the low power requirements of the cpu in sleep mode. i was able to unplug all the cables and walk around with this mac mini with no power and a flashing power light, and i was able to plug it back in, and it would come back. it wasn't hibernating.

    i haven't been able to repeat this experiment since

    i gotta get around to getting another ups on my main time capsule so my entire wfi network won't go down
  6. westom, May 10, 2016
    Last edited: May 11, 2016

    westom macrumors regular

    Nov 8, 2009
    Power loss never causes hardware damage. That urban myth comes from hearsay and advertising to promote expensive boxes. A UPS only has one function - temporary and 'dirty' power so that unsaved data can be saved. it does not do and does not claim hardware protection.

    Well it does claim to do surge protection. View spec numbers. Its maybe hundreds of joules will absorb a surge that is hundreds of thousands of joules? If we ignore numbers, then it does 100% protection. Meanwhile, hundreds joules surge is already made irrelevant by what is inside every Mac and other appliances. UPS has just enough 'near zero' joules so that the naive will *know* it does magical hardware protection.

    Easier is to save files to disk BEFORE going to sleep. Then no data will be lost during any power outage.

    Surges that do damage can be hundreds of thousands of joules. These occur maybe once every seven years. Can overwhelm superior protection already inside a Mac. If a Mac needs that protection, then everything in your building needs that protection. Informed homeowners earth one 'whole house' protector, for about $1 per appliance. Then a rare and destructive surge does not damage a dishwasher, air conditioner, bathroom GFCIs, smoke detectors, recharging phones, furnace, refrigerator, all clocks, a Mac, and even a UPS needs that protection.
  7. roadkill401 macrumors 6502


    Jan 11, 2015
    Westom, you are so mis-informed you are doing a great dis-service to just about everyone.

    Power loss by itself probably will not cause any damage. The issue generally is what happens when the power comes back on. In my area I have had times when the power comes back on, drops off again and then back up again in less than a second. Enough to blow a light fixture. Computers are not simple electric devices and like to have preferably clean and constant power.

    A good quality UPS also provides for a second problem that most don't think of. Brown-Outs. If you are in a city with good clean power then you are lucky. Many of us have a city that in the summer time as power needs exceed the ability of the input grid to handle the load, the local power utility will cycle the voltage from the standard 120v down to 100v. As the voltage drops, the amount of current the utility has goes up and so they can meet the power requirement loads in their system. A lightbulb will just dim. A dishwasher motor will just slow down a bit. A computer however will run out of power and can cause damage. A good UPS can step up the voltage so nothing bad happens.
  8. westom macrumors regular

    Nov 8, 2009
    Unfortunately many do a massive disservice by posting urban myths and fables.

    For example, brownouts are potentially harmful to motorized appliances - ie a dishwasher - despite contrary assumptions. So a utility either maintains voltage or cut off power ... to protect what is at greatest risk: motorized appliances. Utility never drops voltage by more than 5% so that motorized appliances are not harmed

    Voltage can drop so low that incandescent bulbs dim to 50% intensity. Even that is a perfectly good voltage for any electronics. If voltage drops too low, then electronics simply power off - without damage. As obvious even in ATX Standards. Those and other standards are blunt. Low voltage - any low voltage - must not cause electronics damage. One standard includes this expression for all low voltages down to zero. And in all capital letters. "No damage region".

    No damage region includes something called a power outage - zero volts.

    How does power restoration cause damage? A power restoration is a slowly increasing voltage as every appliance restarts simultaneously. Some electronics feature an inrush current limiter to intentionally reproduce this slowly rising voltage. Since a slowly rising voltage can increase electronics life expectancy. An inrush current limiter is found in some electronics to intentionally duplicate what occurs during power restoration. Power restoration does not cause damage.

    Same slowly rising voltage during power restoration can be problematic for motorized appliances. He should have known that. Better is to disconnect motorized appliances (ie refrigerator, air conditioner, furnace) until voltage is fully restored.

    'Dirtiest' power comes from a UPS in battery backup mode. So 'dirty' as to be problematic for motorized appliance. That same 'dirty' UPS power is ideal for all electronics. Neither 'dirtiest' power from a UPS nor a blackout (power outage) cause electronics damage. However hearsay and wild speculation assume otherwise.

    UPS has one function. Temporary and 'dirty' power so that unsaved data can be saved. It does not protect hardware. It does not claim to protect hardware. He posted subjective denials - some even violate basic electrical concepts - because no facts support his allegations. Because he has no numbers to justify what are only personal beliefs.

    Power outage does not cause hardware damage - to light bulbs, motorized, or electronic appliances. A UPS only has one function - temporary and 'dirty' power so that unsaved data can be saved. It does not do and does not claim hardware protection - once myth purveyors are forced to to define an 'at risk' part or provide manufacturer datasheets that define a risk. he provides neither because no such risk exists - once we eliminate fables.
  9. h9826790 macrumors G5


    Apr 3, 2014
    Hong Kong
    I doubt about this. From memory (when I was studying Physics in secondary school), when power suddenly goes out. There will be a short and huge induction current going backward, that can cause damage to the electronics.

    Of course, we can simply put a diode in the circuit to avoid backward current. However, what I want to point out is that power loss can cause damage (on very poor design circuit, iMac doesn't sounds like fall into this category).

    On the other hand, when the power comes back, it does more damage to the power supply then the device. e.g. The whole building's demand suddenly jump from zero to the million watt scale. That may trigger the protection and cause another power loss again. Because the circuit believe that may damage the electrical network, but not the device.
  10. maflynn Moderator


    Staff Member

    May 3, 2009
    You are correct that a loss of power in of itself will not cause any issues, its the possible spike just before it fails, or just as its coming online again.
  11. varian55zx macrumors 6502a


    May 10, 2012
    San Francisco
    I always use a surge protector. Mine has a 3940 joule energy rating. I got a great deal on Amazon I guess because I have Amazon Prime, my old one died so it was time for new one. This thing also is 12 outlet.

    Surge protectors are an absolute necessity, a close friend of mine was having some routine problems with blown fuses in a kitchen, I said you seriously aren't using some sort of surge protector technology? They seemed a little surprised, and baffled they didn't remember the overt usefulness of surge protectors.

    I've always used them with my desktop computer because it will protect the computer, and during, say, and outage, the surge protector will keep your computer protected. That right there is well worth the price of it.

    In addition to that, you can connect anything to it and you don't have to worry about a blown fuse. In my case I have a small personal heater, 500 w speaker system, iMac, and whatever else.

    A power outage, or sudden, unanticipated shutdown absolutely has the potential to damage your iMac, as well as possibly its hard drive to an extent.
  12. westom, May 12, 2016
    Last edited: May 12, 2016

    westom macrumors regular

    Nov 8, 2009
    A perfect example of how fables get created. A spike created by a tree rat, stray car, lineman error, or lightning precedes a blackout. When power is restored, an appliance has failed. Observation somehow 'proves' power restoration causes damage.

    After all, one has a 'surge protector' rated to 'absorb' 3840 joules. That proves a spike could not cause damage? Total nonsense. Destructive surges can be hundreds of thousands of joules. That near zero protector did nothing for a destructive type of surge. In some cases, an adjacent protector may even give a surge more destructive paths into a Mac. Make damage easier. As we demonstrated in the review and repair of a network of powered off computers. An adjacent protector bypassed superior protection in a computer's PSU; connected that surge destructively into its motherboard.

    Wild speculation is somehow 'proof' that a power outage or blown fuse is destructive, that power restoration is destructive, or that near zero joules in a power strip will magically 'block' or 'absorb' hundreds of thousands of joules.

    More facts. A 120 volt surge protector has a 'let through' voltage exceeding 300 volts. That means it does absolutely nothing until voltage well exceeds 300 volts. How does a slowly rising voltage, during power restoration, create a voltage exceeding 300 volts? It doesn't. A surge protector does nothing during power restoration. It does not even claim to protect from typically destructive surges that may be hundreds of thousands of joules. But it sure is profitable.

    To promote sales to people who ignore spec numbers, a UPS will also claim surge protection. A UPS typically has less joules - hundreds. But since it has near zero joules, then it must be 100% protection. Subjective claims can prove anything - when a consumer ignores spec numbers. They are marketing to people who ignore numbers, do not know how electricity works, have no idea what does and does not cause damage. and do not know that all appliances already contain robust surge protection.

    To have surge protection means one installs something completely different -called a surge protector. To protect from an anomaly that can overwhelm robust protection in any appliance. This proven solution is rated for protection even from direct lightning strikes. Lightning is typically 20,000 amps. So a minimal 'whole house' protector is 50,000 amps. This superior solution costs about $1 per protected appliance. And is almost completely unknown to many only educated by advertising, hearsay, and speculation. Even the OP's UPS and a 3840 joule protector must be protected using this well proven solution.

    Power restoration does not cause hardware damage. Power outage does not cause damage. Destructive spikes, that occur maybe once every seven years, are averted by something completely different and called a surge protector. That tiny protector from Amazon does not claim to protect from typically destructive surges. Unfortunately most assume using hearsay and wild speculation rather than learn what really does and does not cause damage. Most ignore relevant numbers.

    OP's UPS will provide temporary and 'dirty' power during a blackout so that unsaved data can be saved. It does nothing and does not even claim to protect hardware. OP should learn about hardware protection that costs about $1 per protected appliance. That is found in all facilities that cannot have damage. It is necessary to protect the OP's Mac and to protect another's 3940 joule protector.
  13. roadkill401 macrumors 6502


    Jan 11, 2015
    Westom. Your OMNIPOTENCE must be legendary and you know all things from everywhere.

    I do woodworking as a hobby and so I do quite a bit with different motors and controllers for them. On my wood lathe I have a 3phase motor and the way you control the speed and direction of the motor is by altering the voltage and the phase of the power supplied. A motor is nothing more than some big winding coils that as electricity is passed through it, a magnetic field is generated. By controlling the timing of electricity running through the coils controls the speed of the motor. Voltage has ZERO effect of burning out a coil. The amount of current does as that is what generates heat in the fine wires of the coil. Too much heat will melt the wire or damage the insulation. Most soft start motors do so by limiting the incoming voltage and ramping it up to control the surge of current that will trip a fuse/breaker.

    I guess also you must have missed reading last summer in my local news paper how my municipal power company will be doing rolling brown outs to deal with the high loads due to the residents use of Air Conditioners. How they were going to be upgrading the transformers to deal with the growth inside the town and asking for residents to consider putting the temperature up several degrees or using a programmable thermostat to set the AC to come on outside of peek power times from 11:30am to 4:00pm.

    You keep on talking about how UPS have the most dirty power. I guess you must be testing some $50 knock off from China that sells on ebay. Look for one with a true sine-wave generator. Yes they do cost some money but not nearly as much as your iMac, and unlike your computer equipment, they don't go obsolete after 3 years. Yes, you do need to maintain the battery packs every 5-6 years, but you get the benefit that 'when' the power goes off, your iMac doesn't. This helps to protect things like your timemachine backup that murphy says will be in the middle of doing it's thing when the power is likely to drop, or worse when you are in the middle of saving something that you've been working on for hours and forgot to make interim saves on
  14. westom, May 12, 2016
    Last edited: May 12, 2016

    westom macrumors regular

    Nov 8, 2009
    A specially designed motor that is speed adjustable by modifying phase, somehow proves all other motors are same type? That motor is not inside a refrigerator, dishwasher, air conditioner, garage door opener, furnace, and washing machine? Appliance motors can be harmed when voltage drops too low. That threat was even defined by a number that was ignored.

    One exception (a speed adjustable motor) proves everything else is wrong? That is disingenuous - junk science reasoning. Others should be criticizing you for posting so much intentionally deceptive logic.

    Ignored numbers will be repeated. How much can a utility lower voltage when loads (ie air conditioners) are excessive? Either a utility must shed load OR lower voltage by not more than 5%. A lower voltage is problematic to motorized appliances. Please reread that paragraph to learn that and other facts that were intentionally ignored.

    A UPS is 'dirty' power. If you know otherwise, then where is your specification number? Junk science and intentionally deceptive accusations are identified by no numbers.

    Some numbers for this 120 volt UPS. It outputs 200 volt square waves with a spike of up to 270 volts. Remember high school math? Those square waves and spikes are a sum of pure sine waves. This UPS manufacturer also claims it is a pure sine wave output. He did not lie. He did not provide numbers that say how "pure" that sine wave" - such as %THD. He is marketing to the electrically naive who also ignore numbers.

    You did not even know a brownout must be less than 5% - to not harm motorized appliances. Which internal part is protected by a UPS? Why is that list still not provided? UPS does not and does not claim to do hardware protection.

    A Mac is perfectly happy when voltage drops so low that incandescent bulbs dim to 40% intensity. What internal part is damaged by a low voltage? None. Mac damage from a low voltage (or outage) is only urban myth created by subjective beliefs - also called junk science.

    UPS has one function. Temporary and 'dirty' power so that unsaved data can be saved. That same power, so 'dirty' as to be problematic to motorized appliances, is perfectly good for all computers. Why would anyone spend $hundreds or a $thousand on a pure sine wave UPS when a cheap and 'dirty' one accomplishes same protection from a blackout? Again, protection inside computers (including a Mac) is so robust that even 'dirty' UPS power causes no hardware damage. Protection already inside a Mac makes anomalies - such as 'dirty' power from a UPS - completely irrelevant.

    Again, leaving it on 24/7 accomplishes nothing useful - as proven by the facts and numbers you cannot provide. UPS does nothing to protect hardware - even proven by facts and numbers you cannot discuss.

    OP asked if a power outage causes hardware damage. Obviously not.

    Meanwhile, the OP should be concerned about a rare anomaly that can overwhelm existing protection inside a Mac and all other household appliances. This well proven 'whole house' solution costs about $1 per protected appliance (many times less than a UPS). With spec numbers that define hardware protection.

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