Just wanted to report a seemingly rare issue I've encountered, I've found one other who has an 850 P2 on the NCIX reviews with the issue, and a mention on forums.overclockers.co.uk. 
You can find others with the issue if you search well.
 
The fan while in Eco Mode will get into an idle state and become stuck there, and over a very short period of time with my rig (4690k GTX 970) in benchmarks such as Unigine Valley or games like Witcher 3, the PSU will become overly hot and shut down the PC to prevent damage. 
Particularly the upper right corner of the exhaust/back (fan face down) of the 650 P2 gets very hot to the touch.
 
When the PC reboots from the unexpected shutdown, the fan will turn back on only until it is cool enough again to go idle, and again, become stuck idle.
I've monitored this with the case on its side, viewing the fan as benchmarks and sudden reboots occur. The rear of the PSU gradually builds heat which is noticeable to the touch.
I don't have any precise measurement tools to give anything conclusive.
 
I just hope it truly does shut down before damage can occur, and that my PSU and other components are not damaged. 
I seem to be very unlucky by getting this PSU with this rare issue, though I know I'm not the only one.
 
The fan works, it spins, nothing is obstructing it, works even in Eco Mode after it overheats and reboots.
For some unknown reason once it gets back to an idle state, it will not spin again. 
That some sort of software issue or something? Since the fan is clearly functional, and at least after the reboot detects the temperatures since it spins.
 
I've yet to switch it to manual mode, but as with the 850 P2 user, I'm sure it will work just fine in that mode. 
It's unfortunate though since I got this PSU primarily because of the Tomshardware review detailing how insanely quiet it was... in Eco Mode... which is broken for me.
 
I would RMA, but it's too late to do so for NCIX since its been over 15 days now. I'm in Canada, and shipping to EVGA in the US is unfortunately a lot more timely and costly.
As long as manual mode functions properly I can still use my PC, and I suppose I have 10 years to change my mind... failed in not even 30 days...
 
I highly doubt there's a solution to this issue but if anyone has suggestions I'm all ears
Hopefully EVGA is aware of this issue and can do something to fix it for future customers
 

Depend of situation, Eco Mode is great if you use 200-300W stronger PSU than need, but if you buy exactly how much need or only 100W more than better leave fan enabled always. From other side that flat part of PSU serve similar to heatsink, and it's not weird to become hot when fan not work. On my Seasonic was constantly VERY hot on touch and fan spin very rear.

I know the selling point of ECO mode is 'silent' operation but is your fan really that loud? My fan in my SuperNOVA 1300 G2 runs all of the time and I can't even hear it.

I've seen some fans that had some weird shapes to their blades that did make a strange noise but I have nine 120mm fans running at 100% all of the time too that might be drowning out any noise my PSU fan is making.

My fans are all pretty quiet. I have two Cougar high static pressure fans on the top 240 rad, three Noctua NF-F12 on the back Monsta 360 rad, two Cougar high air flow case fans on the bottom blowing up into the case and two lighted Corsair high air flow case fans in the front. They're really not at all that loud and I have them at 100% because I don't have any way to put a custom fan curve on them. My MSI Z97 Gaming 7 motherboard BIOS has two panels when entering a fan curve. One panel shows the CPU temp and the other shows Motherboard temp which I think means internal case temp but it doesn't seem to work as I think it should. I think I am only getting control from the CPU temps. One of these days I will finally get a fan controller with some temperature sensors for my case. If my PSU fan ever spins up and gets loud it is during a game and I can't hear it above the game's audio. These Bose Companion 3 speakers were a good investment. I think they have been on 24/7 since 2008 or so and never gave me problems...      yet.

So I've started a cross ship RMA and EVGA is covering shipping both ways which is awesome!
I don't have to spend $30+ shipping something across the continent, and I don't have to go weeks with a non-functional PC because of the cross ship process.
 
Can't stand listening to this PSU fan at idle, it's too loud to always be running.
Under load other things will become louder than the PSU fan which is fine.

Maybe I should have made a special request for EVGA to test the replacement before they send it off.
Watch me get another with the same issue or something

So in the past 16 hours it made it through to 3 different cities in 3 different states and actually got here on time 
The new PSU is good so far, but so was my original for about 20 days, so lets hope this one stays working!
 
I ran the most power demanding benchmark that exists according to overclock.net, the FF Heavensward benchmark for about 30 minutes, and the fan never spun in Eco Mode.
So instead of waiting hours for my extremely air conditioned room to be hot enough, I got a hair dryer, and within a minute the fan started up and I stopped heating it.
My broken PSU overheated and shut off within minutes of running any benchmark in Eco Mode, and the fan never spun.
 
All is good, the fan starts before the PSU overheats.
I can enjoy a silent idle with my Noctua filled PC again, and my GTX 1070 arrives tomorrow!
 
 
 
 
 
 
 
 

Hunched
So in the past 16 hours it made it through to 3 different cities in 3 different states and actually got here on time 
The new PSU is good so far, but so was my original for about 20 days, so lets hope this one stays working!
 
I ran the most power demanding benchmark that exists according to overclock.net, the FF Heavensward benchmark for about 30 minutes, and the fan never spun in Eco Mode.
So instead of waiting hours for my extremely air conditioned room to be hot enough, I got a hair dryer, and within a minute the fan started up and I stopped heating it.
My broken PSU overheated and shut off within minutes of running any benchmark in Eco Mode, and the fan never spun.
 
All is good, the fan starts before the PSU overheats.
I can enjoy a silent idle with my Noctua filled PC again, and my GTX 1070 arrives tomorrow!
 
 
 
 
 
 
 
 

 
I tried eco on/off. Honestly. The fan is so quiet. I cant even hear the thing running. Even under full load. I also remember reading I believe it was from Tom's Hardware or Jonnyguru reviews. The 750w version actually had a louder fan then the 650w version. The 650w version was much more quit by 10-11db or so. Either way. Good to see EVGA took care of you and are back up running!