I hope you are using a 20amp outlet. If its a 15a it really shouldn't be used for mining in my humble opinion.
I plugged a lamp into where I have my 2 Antminer S3+ running. Every minute or so the light flickers slightly.
Anyway to solve this? I am assuming this is inrush current with the mining cores changing clock rates or fans adjusting their speeds.
15a is fine for 2 miners running. I've got 3 on a single PSU pulling ~9A at the wall. What he needs to do is find out what else is on that breaker. If there's nothing else on the breaker then I would suspect faulty wiring or the breaker itself is going bad.