John Rouillard asked for clarification > Ummm, how does that work exactly. Max continual load on any pdu is 80% > of the circuit. ... max continuous load of 16 amps. > > Now if devices D1...DN have dual plugs and one goes to pdu P1 and the > other goes to pdu P2, each pdu will see 1/2 the amperage load
You are correct for the two-phase 120V case. If you go to three phases, then you get P1, P2, P3. Each has 208V @ 20A. For simplicity, let's say I have the following devices that each draw 6A @ 208V. Device A: connects to P1 & P2 Device B: P2 & P3 Device C: P1 & P3 Device D: P1 & P2 Device E: P2 & P3 Device F: P1 & P3 Six devices, 12 power cords, each cord drawing 3 amps. There are 3 PDUs so each has 4 devices connected. Without any faults, therefore each PDU is supplying 12A. Q: What happens when P2's breaker trips? A: Device A and Device D draw an extra 6 amps from P1; device B and device E draw an extra 6 amps from P3. That third phase, wired this way, gives you a lot more headroom in the event of a fault on a single phase. (My example rounds up a bit, to 90% load during a failure; a conservative data center admin will respect the 80% max cited by John.) -rich _______________________________________________ bblisa mailing list [email protected] http://www.bblisa.org/mailman/listinfo/bblisa
