APC UPS/Power supply back up failing

Question

Level 1

4 points

APC UPS/Power supply back up failing

I have been having problems with an APC Universal Power Supply (UPS) that I was hoping would protect my work in case of a power cut. At the moment I have two iMacs plugged into it (nothing else) but last week an alarm went off on the UPS. The alarm apparently means that the unit did a self test and didn't have enough battery power to keep my devices operating. It's very odd as the battery should be fully charged all the time (the unit is plugged into the wall) and it's only a year old.

APC seem to be dodging any responsibility by saying that the UPS (model Back-UPS ES 400) is not compatible with my iMacs. They say that each of my machines is too high of a "wattage rating" and that only devices up to a wattage rating of 240 can be plugged in. I have been unable to find what the "wattage ratings" of my iMacs actually are.

Can anyone tell me how to get the precise wattage rating for an iMac, and can anyone recommend a UPS that actually supports iMacs? My two computers are a "Late 2012 27 inch" and a "2017 5K Retina 27 inch". The model numbers appear to be 13,2 and 18,3 respectively.

Many thanks

iMac Line (2012 and Later)

Posted on Jan 8, 2019 7:27 AM

Reply

Answer 1

Top-ranking reply

iCare

Level 4

2,490 points

Jan 8, 2019 10:34 AM in response to vladc

I have several APC UPS devices which have been in use with my iMac's for over a decade. Since they utilize lead acid batteries I need to replace the batteries about every four to five years. How old is your UPS? For more info on UPS battery life I suggest reviewing the following info:

http://www.apc.com/us/en/faqs/FA158934/

Here is an Apple article that provides the power requirements for iMac products so you can determine whether your UPS can support the equipment you are connecting to it. The UPS model you specified can only output a max of 240 watts under battery power, and your 2017 5K Retina 27 inch by itself has a max power requirement of 217 watts according to Apple's article. I think you need to revisit your UPS requirements and pick a model that more closely matches your power requirements. Make sure you take into account the amount of time you expect the UPS to run your iMac's in the event of a power failure.

https://support.apple.com/en-us/HT201918

Reply

Answer 2

iCare

Level 4

2,490 points

Jan 8, 2019 11:04 AM in response to vladc

Your UPS uses an inverter circuit to convert the DC voltage (likely 6 volts) from the UPS batteries to the much higher AC voltage needed to power your iMac. The output voltage is dependent on where you live (e.g. 120VAC in US vs 240VAC Europe). The UPS rating of 240 watts is the max it can provide for all of the devices attached to the UPS. It doesn't mean that each device can be up to 240 watts. With your 2017 iMac alone you are getting awfully close to the max for your UPS, and that doesn't take into account other factors like inrush current.

I found an APC selector tool on their website that can be used to give you an idea about how long a particular UPS model will operate your equipment in the event of a power failure. In my particular case I want my 27 inch iMac to keep running for at least 20 minutes so I have time to get to it, save my work, and shut it down properly. The extra run time also means I have a much larger and more expensive unit than the one you own. It looks like the model you have would provide minimal run time, even with just one of your iMacs attached to it. Everybody has different requirements. Hopefully you can find a solution that meets your needs. At a minimum you should disconnect one of the iMacs from the UPS.

https://www.apc.com/shop/us/en/tools/ups_selector/home/load

Reply

Answer 3

vladc Author

Level 1

4 points

Jan 8, 2019 10:42 AM in response to iCare

Thank you, I saw that article earlier but could only see the retina iMac listed (with a generic configuration) and not my other one. I'm surprised there is no more specific way to find out the rating.

The company who made the UPS made it sound as if each device just needed to be under 240 wattage rating, but are you saying that it's the combined total of all devices?

Thanks for your help

Reply

Answer 4

vladc Author

Level 1

4 points

Jan 8, 2019 1:17 PM in response to iCare

Thank you so much -- that is honestly very helpful. I will find a more appropriate UPS for my computers.

Thanks again

Reply