New Superflow Power Supply Possible Problem?

[Kellogz]

Installed new pc parts and everythign today, all seems to be fine apart from the PSU while its on the fan appears to start up than stop constantly, wondering if this is normal, if i change the switch at the back the fan stops working completely. Also when the fan does spin there appears to be a slight hum to it.

PSU: SuperFlower Leadex GOLD 1000W Fully Modular "80 Plus Gold" Power Supply - Black

 

[snips86x]

I believe they are hybrid so the fan will only spin at a certain load point.