Originally Posted By: jfarsetta
This post was automatically imported from our archived forum.
Greg,
You will not always have ground lops if the equipment is not on the same physical service of fed out of the same transformer, sorry. You speak of shielded cables, which has been replaced by unshielded twisted cable (category 3, 4, 5, 5E, and now 6). Unshielded cable is the defacto standard, and has ourstripped multi-mode fiber optic cable for speed.
If switches are isolated by optical fiber cabling providing the data pathway, there is no "bonding" between the backbone devices. And, as star topologies from the switches are limited to 100 meters, the chances are good that the switch and served PCs are fed from the same panel or transformer. When you say that there will be "all sorts of ground loops", this is where a good RCDD, design engineer, and electrical contractor or engineer collaborate to develop a real plan.
As to experience, you and I have something in common. While it is true that ROLM was not originally an IBM company, it is not exactly true that only ROLM folks servicesd the equipment. I worked for ROLM at the time. While IBM is certainly a world class company, they fell down with regard to ROLM and some of the technologies ROLM employed. IBM was a mainframe and PC company at the time. IBM sold ROLM to Seimens, which combined their existing switch with ROLM's CBX technologies. BTW, Seimens, Nortel, and AT&T still call for isolated grounds.
In the case of a data center I helped care for at Unilever, we fed the mainframes, and RISC machined via motor-generator, which produced a pure square-wave. Talk about clean! Again, grounding was critical...
But, back to some points... So, are you telling me that the 6611 router didnt call for an IG? Are you telling me that the likes of Cisco, Wellfleet, Nortel, AT&T didnt call for IG?
As to shielded cables between buildings, conventional communications cabling may or may not have included shielding. Multi-conductor communications cabling typically did, but it had little to do with ground loops, and more to do with grounding, period. Analog telecom equipment could care less about it. Dumb terminals with either baluns, or coax, or RS-232 had similar limitations. Again, low speed data.
Again, with high-speed data, copper was limited to 100 meters, so there went the idea of copper inter-building data cable schemes. Optical fiber itself isolated the equipment at each end from creating a ground loop between each backbone device.
Yes, IG receptacles are still called for in many, many applications and with equipment. Single point ground "windows" are also common. BTW, are you telling me that RS6000's dont call for IGs? Or are you saying that they merely call for a single-point ground?
As you mentioned your career at IBM, you should be aware that, I too, know something of what I speak. At one point I was a working Cisco engineer, a certifieed Wellfleet engineer, a ROLM support engineer, a communications distribution design engineer, a data center design engineer, was a Sr. support engineer for Unilever, was Director of Network Planning and Suport for NJ Transit, was Northeast Regional Director of Operations for Bell Atlantic Network Integration, was a Operations Director at Exodus Communications, was a Director of Sales Engineering at Exodus, and was VP or Operations and Professional Services at Generation 360. I am a published author, and used to have a monthly column in the WebSphere Developers Journal, where I regularly wrote about power, grounding, and data center design, business continuity, and operations.
I have been around the block more than once, and have watched much of today's technology be developed and grow up.
We'll have to agree to disagree on this one. But the validity of isolated grounding methodologies remains something we CAN agree on, which is what this post morphed into. 
I apologize to my compadres whom I've just lulled to sleep. Sorry for the thread drift (big time)...
--
Joe Farsetta
Illigitimi Non Carborundum
"Dont let the bastards grind you down..."