nanog mailing list archives
Re: Want to move to all 208V for server racks
From: Robert Bonomi <bonomi () mail r-bonomi com>
Date: Sat, 4 Dec 2010 17:47:29 -0600 (CST)
Date: Fri, 3 Dec 2010 09:42:10 -0800 From: Leo Bicknell <bicknell () ufp org> Subject: Re: Want to move to all 208V for server racks In a message written on Fri, Dec 03, 2010 at 04:57:03PM +0000, Gary Buhrmas= ter wrote:limits so that ones life has increased protection. A protective trip is better than the alternative.Not always. I worked in a data center with something I thought was very, very cool. http://www.hilkar.com/highresistance.htm The concept, at a high level, is rather than tie the (service, not signal) ground back to grounding rods directly you run it through a large resistor. Now when a phase is "grounded" it runs through the resistor, allowing a small but safe current to flow. Why is this cool? Well, say you have a power strip running at 10A with a bunch of servers on it. If you took a paperclip and inserted it in an empty plug connecting hot to ground with a normal system (simulating a faulty bit of gear) the breaker would trip, all your servers would go off. If you did this with a high resistance setup the paperclip would conduct about 0.5A, maybe less. An alarm, dectecting current, at the resistor would go off to say there was a fault. Your circuit would draw 10.5 amps and everything would stay up and running. That faulty bit of gear didn't take down your entire power strip. This totally eliminates arc faults, and there isn't enough current to ground to arc. I think GFCI's are also unnecessary, as the fault can't conduct enough current to be harmful.
All is "well and good", *UNTIL* "something happens" that introduces _another_ path to 'ground' that bypasses the 'high rresistance' links. (Reminiscent of the old "Branch on C.E. grounded" programming joke.)
Current thread:
- Re: Want to move to all 208V for server racks, (continued)
- Re: Want to move to all 208V for server racks Christopher Phillips (Dec 02)
- Re: Want to move to all 208V for server racks William Pitcock (Dec 02)
- Re: Want to move to all 208V for server racks Gary Buhrmaster (Dec 03)
- RE: Want to move to all 208V for server racks Alex Rubenstein (Dec 03)
- RE: Want to move to all 208V for server racks David Hubbard (Dec 02)
- Re: Want to move to all 208V for server racks Jay Nakamura (Dec 02)
- Re: Want to move to all 208V for server racks Mark Kent (Dec 02)
- Re: Want to move to all 208V for server racks Ingo Flaschberger (Dec 02)
- Re: Want to move to all 208V for server racks Seth Mattinen (Dec 02)
- RE: Want to move to all 208V for server racks Alex Rubenstein (Dec 02)
- Re: Want to move to all 208V for server racks Robert Bonomi (Dec 04)