What Power Supply are you using? Almost guarantee this is the issue.
If the PSU is good, do you have PDU that you're connecting these too? If so, what is its amp rating?
2 S9s running on a cheap 12-16A PDU will trip it and shut it down.
No PDU. Sub Panel in the garage, only being used to charge my car and power the miners right now (And the Switch & Laptop).
The miners are on a 240v 20 amp breaker. Voltage under load is 241v right now.
The PSU is the APW3++ from Bitmain.
So new development.
For sake of ease, the "problem unit" discussed above will be #1, and the second will be #2.
#1 will act as mentioned above .
#2, stays online and functions considerably better. Usually #1 will have the drop outs as described above, but now, sometimes, both #1 and #2 will disconnect and cut out at the same time. Red flashing fault light.
I have a laptop (Dell Mini 9 Ultra Low power netbook) on the bench with the miners as a monitoring/control computer (I've had it for years, and too slow to do much else). When the miners are offline, the netbook still has internet access. I have it plugged into the "mining switch" instead of on WiFi.