Using multiple phases on a c7000 Single phase chassis

[darrenjmurphy]

We are installing c7000 chassis in a new data centre that uses racks equipped with the new Rittal PSM solution for modular power distribution. See http://www.rittal.com/products/katalog.asp?ViewAt=5-36-3108-3108&Dom=si&lang=GB&NavName=Three-phase%20socket%20strip%20up%20to%2096%20A,%20Power%20System%20Module%20PSM This provides the necessary IEC320 C19 sockets to power a single phase c7000 (equipped with C19 plugs) chassis across two feeds however it is a three phase power bar which would require that I run the chassis PSU's across three phases. This would result in the following configuration PSU1 Phase 1 - Feed A PSU2 Phase 2 - Feed A PSU3 Phase 3 - Feed A PSU4 Phase 1 - Feed B PSU5 Phase 2 - Feed B PSU6 Phase 3 - Feed B I am struggling to find any definitive information on this configuration and whether it is supported the c7000 certainly has a 3 Phase option which as far as I know only changes the power interface not the PSU's themselves.

[Tony Harvey_1]

This will work the c7000 does not care which power supply is being fed from which phase. The site planning guide at www.hp.com/go/bladesiteplanning has soem details on this.

[chopper3]

It may well 'work' as in fire-up but any power engineer will tell you that what you're planning on doing is extremely dangerous - you should never mix phases in the same rack as there will almost certainly be a potential in the earth. It's a really, really bad idea - call up your M&E guys if you don't believe me. As a rule of thumb you should earth each rack individually and never use more than one phase in a rack (unless you're using three-phase that is, when the rules change).

[darrenjmurphy]

I used to operate to the single phase per cab topology but there's more requirement to get more current into a single rack these days hence all the 3 phase PDU designs coming from APC, HP and Rittal. I had an opportunity to speak to an APC electrical engineer here in the UK about the my c7000 issue and he was more than happy to run with multiple phases across the chassis as long as the rack earthing was good. Most multiple rack layouts are bonded together mechanically and electrically anyway so it practically impossible to get away from having a mix of phases.

[Tony Harvey_1]

I'm with Darren on this. In a Tier 4 or Tier 3 datacenter, by definition you have feeds from different UPS, distribution panels and different providers so you will have mixed phases in the rack. Using solid grounds/earths in the rack and a good building ground/earth will resolve any problems and the c7000 was designed to deal with each power supply being on a different phase.