Dude. Buy a KILLAWATT meter at harbor fright or something! You have to know wall watts if you load it that close to the max!
Depending on the efficiency of that PSU you could have been drawing 620W for the S5 and 380W for the S3 for a total of 1100W (@ the wall)!
I always try to shoot for at least 10% LESS from the wall than the PSU ratings, if its a good supply. (ie 1200W wall draw on a quality 1300W PSU would be the maximum I would go, 1300W max should be the DC number before conversion so theoretically you could go 1400W+ from the wall but 100% loading 24/7 is a great way to blow out a PSU as you just found!
Knowing the wattage at the wall does not necessarily tell you what the miners are drawing in DC from the PSU. PSU efficiency varies by model, by individual PSU, by input AC voltage and by load. Here is the 80+ Rating chart to show you the variation:
Manufacturers like Bitmain are usually pretty accurate on their miner's efficiency ratings IME. Most of them factor a PSU efficiency of 90% when giving their ATW rating, except for the S7 which uses 93% as their ATW rating. An s3+ draws ~325W DC, and an S5 draws ~530-550W DC, for a total of <900W. The nice thing about server PSU's is that they typically have good thermal shut-offs, and usually come back to life after tripping them. So, if in your ambient temperature that specific load isn't working for you, start downclocking the S3+ until it stays alive. My experience has been that 90% DC load is a good maximum when dealing with Server PSU's, depending on the model and the ambient temperature in your mining area.
