Thought I had seen it all - as to what will be tossed at Homeowners + DIY's from Home Centers, but that IG thing has to be the most lame one yet!
We did install lots of IG Circuitry + Receptacles in the Banks, loan centers, training centers and data centers, back in the 80's - and still a few up through the 90's.
As many have said before, far too many IG Circuits were installed improperly, and were more of a problem than solution.
The concept is very simple:
"Star Point Grounding"
- all IG Conductors for Branch Circuits terminate on a dedicated bus kit, which is isolated from the Panelboard's enclosure.
Feed this IG Bus with a suitable sized Conductor, which is bonded at the same point where that system's GES is bonded - typically at the Service Equipment if the service is 150 VAC or less to ground (120/XXX Volt system).
If a Customer-Owned Transformer is used (to create an "SDS" with 120 VAC to Ground from some other system), the IG "Feeder" Conductor bonds to the same _Star Point_ where "X0", the GEC, Common (Neutral) Grounded Conductor(s) and Equipment Grounding Conductors all terminate.
I still deal with IG Circuitry + Concepts, but not for any Data - related loads.
They now appear in Audio / Video / Technical Lighting applications, where they are effective in eliminating Ground Loop interference.
On most of the Audio Systems, the racks incorporate "several levels of IG concepts" - such as:
* Receptacles mounted to a metallic frame (rack),
* Audio equipment mounted to same frame (metallic enclosures),
* Branch Circuitry feeding the frame has "Isolation" between metallic Conduits and the rack, via Non-Metallic whips,
* Branch Circuitry includes an IG Conductor - which terminates to the rack only, and runs isolated and dedicated to an IG bus kit at the Panelboard,
* IG Bus at Panelboard is "Fed" via #8 or #6 IG Conductor, terminated at the Power System's "Star Ground Bonding Point"
Video IG Circuitry is done in "The Standard Manner":
* Each Receptacle has a Dedicated, Isolated Grounding Conductor run back to the IG Kit at the Panelboard,
* IG Bus at Panelboard is "Fed" via #8 or #6 IG Conductor, terminated at the Power System's "Star Ground Bonding Point"
However, most A/V firms are using modulated signal lines, so IGs are not needed.
Wonder what havoc would be encountered, if someone was to mention to the Big Box Customers that:
*** NM Cable, Non-Metallic Outlet Boxes and Standard Grounding type Receptacles used together, is already an Isolated Grounding Circuit!!! ***
I might toss this out as a loaded question, if I stumble across one of the "How-To" Seminars... maybe...
Back in the day, when (some) Banks first started using "TCDs" (Teller Cash Dispensers), the Machine makers + the Vendors demanded Dedicated IG Circuitry for the TCDs.
Some over zealous techs would arrive on site with the Ideal Circuit Analyzer in hand, refusing to perform an install because of Volt loss between Line and the IG (typically across a Circuit length of at least 100 feet), claiming:
"The Electrician Did Not Install an IG Conductor"
or
"EC Installed It Wrong"
- based on _ANY_ Voltage Drop measured with the Circuit Analyzer.
Took many Receptacles out, opened Panelboards + J-Boxes, all to "Prove" the IG Circuitry was installed properly.
The techs figured I was only some joker, sent to a site to let them in and out of the Branch; so needless to say the "Poop Would Flow Well" for at least 30 minutes - or as long as it took for them to refuse an installation.
After about 10 of these scenarios, I just began opening things up prior to their arrival! Almost every Branch would have new techs, so I became kind of fluent with the "Debunking Procedures"!
Eventually, the Banks we dealt with demanded "Qualified TCD Installers", which ended the baloney all together.
This was mostly from my discussions with the C&D staff, and a great reputation with them.
BTW, The craziness over IG Circuitry was an inclusion in the warrantee of the machines.
As anyone who deals with "Technical Business Equipment" (Data Equipment, ATMs, etc.) would know, warrantees are very serious things at time of installation!
I dealt with IBM, NCR, Diebold and ADT equipment + techs for many years, and always resolved issues concisely and friendly; but the first wave of TCD Installers were just way too arrogant to listen to some "High Paid babysitter" (referred to me as that).
Strange stuff took place in my previous line of work, during the period between 1994 and 1999, where Data Systems were involved.
LAN Cabling crews were made up of 3 guys, with a combined experience of maybe 1 or 2 years regarding not just their work, but All Construction combined.
Many were eager to learn as much they could from experienced people; a few were not so eager, and a handful looked for any excuse to not work (90% of this work was night work, so I could understand the reluctance!)
"Off-Brand" Spec Equipment installers were the most difficult ones for all on a project.
Sorry for the ranting!
Scott
