The 110 socket is reporting 117v on my voltmeter.  I would like to power them on the 208v sockets, though, since I'm sure it's better for them.

The PDU supplies 110 to the outlets.  There are 21 outlets and 7 are on L1, 7 are on L2, and 7 are on L3.  Each line is a 110 hot just like a normal circuit.

The 6 big outlets with twist locks are (A) two outlests for L1-L2, (B) two outlets for L2-L3, and (C) two outlets for L3-L1.  These outlets bridge two 110's together.  Bridged, they provide 208v.  That is how the PDU can supply both.  On its spec sheet, it says "Nominal output: 120v, 208v."

Using the 20A tab in this spreadsheet, if miner A and B are operational and miner C stops for some reason, the line loads would be L1: 6.8amps, L2: 11.8amps, and L3: 6.8amps.   Would this phase imbalance hurt the miners?