Why does my iMac go to sleep while I am using it?

My iMac (2014) running OS X 10.11.3 goes to sleep every now and then several times a day while I am using it.

I do not lose any work, but it is very annoying. I do not have any hot-corners for sleep, or Energy Saver settings that cause the behavior.

After monitoring my machine using Terminal:

pmset -g pslo
2016-03-08 17:52:48 -0600 IORegisterForSystemPower: ...Sleeping...

When the event happens, I checked out the logs:

Console.app > System Log Queries > All Messages

3/8/16 5:52:48.206 PM CommCenter[299]: Telling CSI to go low power.

Why is CommCenter telling CSI to go to low power while I am actively using my iMac?

Solution 1:

Well, that did not work. Now I'm going to try this in Terminal.app for 5 hours of "don't go to sleep on me":

caffeinate -t 18000

Info on that command is:

man caffeinate