Should be fine, yeah. 120V 15A, would give you 1440W of AC input (assuming 80% continuous draw as safety margin). If the circuit is running only that miner, this gives you something like 1300W of DC output, which an S7 would only request what, 1000 to 1200 depending on batch/model and clock setting?
I'd put the 1000W across two blades, and the 750W across the third blade and controller. That'd keep both of them at about half power for good efficiency.
good