I will be wiring a church audio system and I'll be using MC cable and isolated ground recepticles. I know there are many pros and cons about the practicality of IG but I decided to go with it anyway. When I install the recepticles in a metal box do I still need to run a EGC to the metal box separate from the IG because of the metal box? If so, how do you guys and gals do it with MC? Thanks for your oppinions even if you think I am nuts.
Forgeting about the pros and cons, if you have decided to do this, you have to keep an eye for the small stuff. After all the work you do to keep the grounds separate it is incredibly easy for something small (like a metal plate) to tie the two back together.
We do a lot of office cubes with both IG and regular outlets, all it takes for the two systems to be tied together is one person to plug the florescent light that is fastened to the grounded frame of the cube into a IG outlet and you now have isolated ground jumped to the equipment ground through the cord of the light.
I see very few times where the two grounds really stay separate.
[This message has been edited by iwire (edited 03-29-2003).]
Bob Badger Construction & Maintenance Electrician Massachusetts
This is copied from Bryants website and says the plate screw is isolated from the ground terminal on the device
Characteristics of Isolated Ground Wiring Devices Isolated ground devices help limit electrical noise on the equipment grounding circuit by providing two grounding paths for the installation. The device grounding circuit terminal and grounding contacts are isolated from the grounding path of the metal outlet box, device mounting means, and metal cover or wall plate, thus establishing a separate, dedicated equipment grounding path for connecting noise-sensitive equipment.
250.119 (B) says "where the condiions of maintenance and supervision ensure that only qualified persons service the installation. "
That statement doesn't apply to most church maintenance men
[This message has been edited by txsparky (edited 03-29-2003).]
Great, Thanks. You guys anwsered alot of questions. I will check my supplier for 12-2 MC IG. Also, I considered using 12-3 and taping the red but I didn't think this would be an acceptable method. I appreciate the responses. Blessings, Mark