All of this discussion about the overall wattage of the PSU, line (mains) voltage, PSU efficiency, etc is driving me crazy (and it's a short ride for me). Here is how I see it.
PSUs have one or more rails that deliver +12V; the 12V rail(s) has/have a max rated amperage; the 12V rail is the only "part" of the PSU the S1 uses; therefore overall PSU "wattage" is not a limiting factor. If the Ants you connect to a PSU draw more power than the PSU's rated +12V amperage, you will shut down the PSU (best case). We can express "power" in this case as amps since we know we are always talking about a 12V system.
Bitmain says the S1 draws "360W from the wall". To give ourselves some headroom / room for error and variability, let's assume a non-overclocked S1 draws 30A (360w / 12V) from the +12V rail. If the BM statement is accurate, you will actually draw less than 30A at the 12V rail(s), but that's OK, we want a margin for error / variability in the amount of power we think the S1 draws. [Note if anyone has actually measured the amps drawn at the 12V rail, we can significantly refine our calculations]
Therefore, if you have three non-OC'd S1s on a given PSU, it better have at least a 90A rating on +12V rail. Looking at the BM chip spec and doing a little math, it appears that if an S1 is OC'd to 400MHz it will draw just over 38A. If you are connecting three S1s OC'd to 400MHz, your PSU should be rated at 115A on the 12V rail(s).
We may have built in more headroom than necessary (we essentially assumed the PSU is 100% efficient, which is clearly impossible) and you may be able to get away with a PSU with it's 12V amps rated at less than that calculated above, but my sense is that we should keep an adequate margin for variability in the amp draw for a particular Ant at a particular moment in time.
I think you're correct about all the facts. Except folks shouldn't be OC'ing to 400MHz. There are other ways to get 200GH/s out of it w/o going that high. Mine are running at 393, and running just fine at 200GH/s. According to my Kill A Watt, which doesn't lie, I'm pulling 10.65A @ 115V for 3xOC'd S1. That's 3.55A a piece @ 115V. Drop that down to 12V and you get 34A a piece. 34A * 3 = 102A on your 12V rail.
My Rosewill 1300 gold is rated at 108A on the 12V rail. That gives me 6A to spare.
My Thermaltake 1200 gold has a 85A rail, and a 40A rail. As long as I put one S1 on the 40A, and the other two other 85A, I should be able to drive 3xS1 OC'd just fine. Hopefully the 40A rail isn't on the CPU connector, cause I'm not mangling my PSU!
Thanks for pointing out the reality about the wattage. I overlooked that. That means I can use my 1200 (which right now is a backup).
EDIT: I forgot about the PSU overhead. With a gold/plat, you can assume 90%+ efficiency. So when an OC'd S1 is pulling 34A, 90% of that is the Ant (30.6) and 10% is the PSU (3.4). If you're using a 80% efficiency, you're going to be pulling 38.25A per OC'd S1.
M
why not oc to 400 ?? i have four of my six ants oced to 400 and they get 200-205 g/hs. .. and they are running nice and cool too with the added aluminum heat sinks. all are under 50 degrees and a couple are even under 45 degrees. i have not seen a single issue running these at 400. i have one that i did not oc because it has some issues with thermal paste bleeding so i left it at stock because it is running at 45 degrees, and i have one more running at 375 oc for now. ocing ants i think is about the heat. as long as can keep their temps down then should be fine.
It works just fine,but they should at least reset to stock clocks............ 
