Hi Rich:
In message <[email protected]>, "Rich Braun" writes: >One of the other issues you should address is fault-tolerance; if a >breaker pops, does your gear stay up? I laid out the racks with >color-coding across the 3 phases (each PDU is labeled its >corresponding color) and made sure each dual-powered device was >attached to two differently-colored PDUs. This is another argument >for 208V rather than 120: you get three phases instead of just two. >Hence you can spread dual-powered devices in such a way that you can >use 12A to 13A of each 20A circuit rather than only 8A to 9.5A. >Exceed those limits, and a single fault will trigger faults on the >other phase(s). Ummm, how does that work exactly. Max continual load on any pdu is 80% of the circuit. So for a 20 amp circuit, you can have a 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 of the devices. If the pdu's (P1, P2) are each on a 20 amp circuit, I claim the max continuous current on each pdu is 8-9 amps or 1/2 of the continuous circuit capacity. If that isn't done what happens if the P1 breaker trips? The 1/2 of the load being borne by P1 now is pulled from P2 which means P2 now has a 16/18 Amp load, which is within its 20 amp capacity and your equipment stays up. If as you claim I use 12/13 amps on each pdu then when P1 fails I load P2 with 24+ amps. This should trip the breaker supplying P2 since that is not just a surge load for a few milliseconds but the new continuous load. What am I missing in your argument? -- -- rouilj John Rouillard =========================================================================== My employers don't acknowledge my existence much less my opinions. _______________________________________________ bblisa mailing list [email protected] http://www.bblisa.org/mailman/listinfo/bblisa
