I'm no expert on electrical but have been around it. A 15 amp circuit does not have enough power for an S9 and an AC even if you step it up. You need to get some real 220 volt power in there. I think it was low voltage that killed them. Plus the temp you noted are pretty hot, especially if that is the board temp. Still pretty warm even if it is the chip temps. Do you have the exhaust vented outside? If not make sure you do that. Do not try to cool the exhaust air it just cost a lot of money for AC and doesn't work.

Good luck!