The power supply gets hot when idle. What can be wrong?

Question

Iron

Hello.
I assembled a computer the other day, all components are new. Average system: i5 8400 + GTX 1060.
First there was a Cougar VTE500 power supply, which I bought just for this system, along with all the components. It seemed strange to me that the fan of the block worked louder than other components, I changed it to a more powerful one with a margin, so that in idle time it certainly would not spin on the vaunted Deepcool DQ ST 750W.
The latter works much quieter, BUT! At idle in a rather cold room, when the computer is not loaded at all, the fan blows out quite hot air. This is rather strange, given that in idle time such a system does not consume anything at all.
I have had experience with a Corsair PSU and clearly remember that the unit is cold when idle and the fan is not spinning.
Now I have a suspicion that the motherboard is not in order, which consumes wildly energy in idle time, perhaps due to technical problems. This is ASRock B360M-ITX/ac.
I also wanted to buy something branded from MSI or Asus, but the budget was limited, plus no upgrade is planned, the computer is exclusively for work.
All characteristics:
Video card: Gigabyte 1060 3gb Mini
Processor: i5 8400
Tower: Xilence M403 (great tower, it can cool 8700 in terms of temperature and eff.)
PSU: Deepcool DQ ST 750W
500 GB SSD M.2 drive Samsung 970 EVO
What could be case? Why does the unit blow hot air when idle.
In the system settings, the power preset is: High performance. But I don’t think that this somehow affected, previously this was not the case in other system engineers.
What and how to check, what do you advise?

Answer 1

Replacing the PSU with a Corsair RM650x solved the problem.
We needed a block with a semi-passive mode.

Answer 2

The above is generally correct. But there is still a moment - with a high performance preset, the computer keeps the percent and other components working by 50% or more. If the PSU stands as a cooler inside the case and takes air from there, then this is not surprising.
If the PSU is turned down to the floor and takes in cold air, then this is certainly strange.
View AIDA64 load on the PC and voltages, maybe the PC is busy with something and sausages)))
Use the normal ones in my understanding of the PSU, thermals. 750w is overkill here. Enough 550 with a margin.