i actually own the 1000W model Seasonic which is similar to the X850's shown in the pic. the way they're oriented in the Sierra, air will be drawn in the back and exhaust out the side (top of the PSU) as we have been discussing.
no big deal.
Lulz. The contrarian power supply.
"We did it because it makes no sense & takes extra time & effort. And because we plain old want to troll you
" --The Hashfast Kids, laughing all the way to the bank.
I find the liquid cooling arrangement far more alarming. These are supposed to go in standard server racks, correct? Then either the coolers will be venting hot air out the front (wrong direction) or flooding the case with hot air. Really dumb.
i actually brought this up to Simon about a month ago via email. here was his answer:
"Data center requires airflow front to back. PSU must be in the back, so rad will not fit in back. Rad needs coldest air, to provide maximum cooling. Air is moving so fast it does not get that warm, so this is the best config."
1. The radiators go in the back, the PS get tossed into a trashcan & a single 1600W PS installed, the way all the cool kids do it.
2. Cool kids know that PSs can go anywhere, including the front.
3. Who in the world decided on 3 chips per 4U box?
etc., etc., etc. Retardation reigns.
*The whole thing reeks of afterthought engineering. As i looked at their 2U variant (now abandoned for a box twice as big), i wondered about the special radiators they had to use to cool 900W. What fan setup? Well, turns out it was just a bunch of bull, now replaced by this 4U botch job.
I made a whole bunch of posts with pictures of airflow & examples -- convinced no one 
