 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
207.91.86.2
In Reply to: Re: Using the same outlet not an option posted by Soundmind on March 15, 2005 at 10:57:22:
I thought having multiple ground rods was also a code violation. Again, there is the potential difference between the two of them that compromises their safety.In any event, the 25 foot extension cords are looking better and better, I'd say! ;-)
Seriously, Maybe our guy would be ok if he had all of the outlets in the room running off of one subpanel, with individual cables running from each outlet box back to the subpanel, rather than "daisy chaining" the outlets on a single cable. If there were equal wire lengths (and nice, tight connections) between each of the outlets and the subpanel, that should eliminate -- or nearly eliminate -- any possiblity for a ground potential difference to exist. Then the subpanel would be grounded to the main panel and would furnish a common safety ground for all of the outlets. It would be almost a "star" ground arrangement.
I think that would work.
Follow Ups:
You cannot find the offending piece of equipment? Something is bringing in this loop. Are you next to another home that has large AC motors? Once we bonded the neutral and ground together for safety we created a whole new power conditioning industry.
As I thought I said, IMO a star ground will not fix the problem. That's because there are multiple paths to a common ground point through each of the signal grounds where they interface the star. For example, the Preamp signal ground may connected to the safety ground at the preamp but also through the signal all the way to the subwoofer and then through the subwoofer connection to the safety ground. A panelette would not be necessary to create a local star gound, just tying the grounds together from the three outlets at the nearest common point possible and using the largest gage ground wire for them. This would ential replacing the 14/2 Romex with something heavier such as 10/3 Romex. (BTW, this would also entail bringing the home runs from all three circuits into the same junction box if they are on separate circuits.) This would not eliminate the problem but it would reduce it by reducing the impedence of segments of the loops.Driving a new ground rod for a clean signal ground would be permitted because it will not ground the neutral at a second point. The neutral is grounded at the service entrance to the house. Redundant grounds of this type are permitted (I'm about 99.9% sure, any electricians in the audience?) The clean ground would then be used as a zero ground reference for the signals.
Another more drastic solution is to replace the AV equpment where the design floats the signal ground with respect to the safety ground. Equipment with balanced inputs always has this configuration. My Marantz 3800 preamp has this configuration but my HK Citation 11 doesn't. With the HK in my system, I had a ground loop due to using two different Cable TV outlets in the same room, one for my VCR and one for my TV set. When the audio signal was connected, it formed a ground loop. The solution in my case was to use only one cable TV jack and run a longer wire using a single RF input on the back of the set.
Sorry you cannot run the equipment grounding conductors to a separate ground rod. NEC says they shall travel in the same raceway or cable as the current carring conductors to the source they are fed from. This would be the panel the branch circuits were fed from. Only in old 2 wire installations will they allow exceptions. But in no case does the NEC allow a separate ground rod as you suggest.
Where does NEC say that? This is a signal reference ground, not the primary safety ground. I do not see anything in NEC which prohibits redundant grounds as long as it doesn't ground a neutral at a second point which this doesn't. If what you said were true, any metal chasis of any equipment in an industrial building which somehow came in contact with building steel, with a steel duct which must be grounded itself, or a cold water pipe would be a code violation. So would all of the quiet grounds in every telephone CO, all computer mainframe data centers and network installations, and laboratories. In fact, as I recall, at some point, the quiet reference ground MUST be grounded to the building safety ground.
Acually the steel structure of a building and the cold water piping system of a building are bonded together and the grounded ac power system is bonded to that. This is all part of the Grounding Electrode System.The NEC does not recognize your signal reference ground. Can you give me the Article and section. The equipment ground on the receptacle shall be connected by the equipment grounding conductor, to the AC grounded electrical system. This is indeed a safety ground.
Nec 2005 NFPA 70
250.4, {A}, {5} Effective Ground-Fault Current Path.
250.32,{B}, {1} Equipment grounding conductor.
250.54 Supplementary
250.130, {C}
300.3, {B} Conductors of the Same Circuit.
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2013, Audio Asylum, all rights reserved ]
[ Take5 ]
