Grounding Question , is this allowed?

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Old 10-07-15, 07:53 PM
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Grounding Question , is this allowed?

I am having a ground loop with some electronic equipment because of running off two circuits. Not getting into the details of that (I have tried a lot of solutions and continuing to troubleshoot), one last ditch solution may be re doing the grounds for the two circuits, but I am not sure if this allowed by code (or a good idea in general). So here is the setup I am thinking about trying:

1. 20amp line to the room , 12/2 , one socket
2. 15mp line to the room, 14/2 , tons of sockets, lights, etc
3. Put both breakers on the same side of the main panel to keep in same phase
4. Now this is the part I am not sure about, can I run the ground from the 20amp socket to a 15amp socket (4inches away) and tie them together. Once they are tied, disconnect the 15amp ground from the main panel and only utilize the 20amp ground?

I read something similiar to this when running multiple lines in a conduit but utilizing one ground. The only restriction was that the largest ground line be used.

Overall this seems sketchy to me, but it would create a single ground for both circuits and hopefully remove the ground loop issue I am having. Be gentle
 
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Old 10-07-15, 08:50 PM
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Panels have both legs on both sides of the panel. They are not left- right, but ABAB top to bottom.

If you have two circuits in the same box both grounds should already be spliced.
 
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Old 10-07-15, 08:55 PM
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Right, this may or may not make sense but my thinking was when dealing with ground loops the run of the ground comes into play so if I tied everything at the room instead of the box and ran one ground to the box it may help alleviate my ground loop issue.
 
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Old 10-07-15, 09:12 PM
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The ground plays no part in the normal operation of the circuit. It is for fault conditions.
 
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Old 10-07-15, 09:32 PM
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Technically ground plays no part in the operation of a circuit but that isn't always the case with sensitive equipment.

I have a pro sound company and run into ground loop problems all the time.

What type of equipment are you running ? Audio ? Audio hum problems ?
Does the equipment all have three prongs ?
 
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Old 10-08-15, 06:09 AM
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No, Romex cable grounds must continue using the equipment grounding conductor within each respective cable back to the panel for each branch circuit.

But, if two branch circuits' cables should enter the same box, all the equipment grounding conductors for each (incoming and continuing cables) are tied together and the ground paths for each circuit back to the panel must coexist as redundant. (Neutrals for different branch circuits may not be so interconnected.)

To alleviate ground loop problems in electronic circuits you may run a separate ground wire daisy chaining from each piece of equipment to the next, attached to the shell of an input jack or output jack or attached to a screw that penetrates to the equipment chassis. Sometimes a stud with a wing nut is provided for this purpose. The far end of this wire may be attached to any known ground, possibly the screw that holds the cover on an outlet box.

Yes, when multiple branch circuits share a plastic conduit, only one EGC, sized for the maximum amperage circuit within, need accompany the circuit conductors.
 

Last edited by AllanJ; 10-08-15 at 06:25 AM.
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Old 10-08-15, 06:27 AM
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The ground loop is occuring based on the equipment being split across two circuits. For example my PC (3 prong) is on the 15amp and the Amplifier (3 prong) is on the 20amp. My receiver is 2 prong and it doesnt matter which circuit it is on, it doesnt have an issue. The issue occurs because the HDMI line of say the computer comes into the receiver and the receiver goes out to my amplifier via rca. The hdmi line has one grounding point point based on the 15amp line and the rca grounding based on the 20amp line. When they meet at the receiver it causes hum on the amplifier speakers.

I have tried grounding the chassis, moving the breaker to the other side of the box,checked the socket wiring, and moving the equipment around on the circuits. The only thing that has fixed the hum is when the component with HDMI and the amplifier are on the same circuit, but that isn't feasible in my room and defeats the purpose of having the two circuits.
 
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Old 10-08-15, 05:30 PM
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Figured I would update this since I think I got it solved, for anyone who searches for this type of thing. Different combinations of grounds and plugs and lots of trial and error. Ground from the UPS to the Receiver and a ground from one amplifier but not the other to the receiver cleared the loop. I moved the breaker to the same phase as the other one but not sure if that helped. Didnt touch the grounds though Thanks for the replies.
 
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Old 10-09-15, 10:46 AM
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Optical fiber is nice! Once you depend on phono plugs carrying millivolt signals with frame ground signal reference, things can go downhill fast.
 
 

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