-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 - --On Monday, January 13, 2003 13:35:14 -0500 blitz <blitz@macronet.net> wrote:
I find the same Kevin..I've done a lot of work in broadcast stations as well, and ground loops are a constant problem. Hum is introduced into audio lines, even in balanced pairs, and Cat5 is not much different.
Read the articles at www.compliance-club.com -- there is a two-piece article on audio systems, by the technical manager at Cadac. It definitely goes against all gut reactions we've forced ourselves into; especially in the telco/audio business. But it makes sense! It works! And, usually the audio folks were the last to find out: Look at your average network component; the grounding scheme of a big modern router. It is mesh grounds all over the place -- and because it is the only way it will ever get the box approved by FCC/UL/CSA or any similar agency.
In a high rise, I can see a neutral failing somewhere on a high floor, and that piece of #10 going incandescent, setting fire to anything combustible between the floor its terminated on and earth ground. (The resistance of an old steel framed building is NOT always lower than that piece of copper, especially old riveted buildings).
Which is why one must construct a low-resistance/impedance mesh, connecting shields and grounds all over the place, so as to short out the potentials. The steel frame could serve as one of these grids, but probably needs to be augmented. And, I wrote "AWG way below 10"... If it is not enough, get a thicker one, and get a new electrical contractor. (see below)
Maybe they do it differently in the EU, but fire safety is also a concern to me.
If you have potential differences like these the house needs a new electrical grid. Wait, that means that the entire North American continent needs rewiring ;-) Anyway, the mains PE MUST be made the best path home, and in a fail-safe manner.
Thank you, but I'll ground nearest to the earth, common bonded point. Its served me well over the years.
Look at the emissions that manage to get into a star grounded, one point only system vs emissions bounced off a mesh grounded system with a decent EMC testing rig and repeat that phrase afterwards ;-) - -- Måns Nilsson Systems Specialist +46 70 681 7204 KTHNOC MN1334-RIPE We're sysadmins. To us, data is a protocol-overhead. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.7 (OpenBSD) iD8DBQE+I1NT02/pMZDM1cURAtDHAJ9AwED4nokCNsotQjrNzbkG751m5wCfT2/R a5z6Hij53cuK4UZTwdHxqiE= =elgF -----END PGP SIGNATURE-----