What is the type and capacity of the current electrical service and the BTU of the AC?
If the AC was sized for normal industrial use, your current 13 S17s are probably already using up most of it's capacity. Also figure in that if you are using AC to remove all the heat generated from the miners that it's going to use about 25% of the power used by the miners to run the AC. So for every 1000W you use on miners, you'll need to calculate (at least) an additional 250W for the AC. I think most mining operations are using large evaporative cooler setups with huge fans.