I have a Thermaltake TR2 RX 550 Watt PSU

http://www.thermaltake.com/products-model.aspx?id=c_00001556

It has 2 x 12V rails from each 19A, but has 3 connectors and a pcie connector.

My motherboard use 18 Watt in total

https://www.asus.com...rboards/E35M1M/

I have 9 Sata disks connected split over 2 connectors, while the 3rd connector feeds the case fans.The only thing else that is connected is a 4 port Sata extension card.

9 Sata disks would mean a maximum power usage of 72 Watt according to the WD spec, but lets assume that at start up spin they use 9 x 20 Watt = 180 Watt

Yet my motherboard reports frequently power surges at start up. I'm thinking that the disks are all connected to a single rail, which will provide only 228 Watt ( 19A x 12V ), but I can't figure out which of the connectors use which rail.

Someone can help me out with this ?

sence your mother board is an asus,

go into the bios, under power

make sure that anti surge support in "Enabled" ,default is disabled.

that shoud take care of the problem

sence your mother board is an asus,

go into the bios, under power

make sure that anti surge support in "Enabled" ,default is disabled.

that shoud take care of the problem

Anti surge support is enabled, that's why it warns me that the previous start up a power surge was detected, but I assume that with a 550 Watt PSU if correct connected this should notbe possible.

If all harddisks are connected to a single 19Amp rail, there is a small chance I would say, that's why I try to find out how one can be sure that half of them are connected to 1 rail and the other half to the second rail.