Electrical Question...Help!!

[LDQ]

Hi all,

I need some help in trying to figure out how to setup the outlets for the control room- vocal booth - and studio. I will be using 1 circuit separated from the lights-and AC/Heat circuits. I know I need to setup the outlets using the star earthing technique....but now this part is what I am confused.

Please check the drawings and let me know which option is the correct way to do it or if both are wrong. In both cases all outlets have 1 common ground at the circuit but is it ok to connect grounds from outlet to outlet or do I need to extend a separate cable from each outlet's ground to the main circuit ground.

Regards,

Luis.

 

[LDQ]

Here is the other drawing

Option 1

 

[Son of Mixerman]

Diagram number 2. Using junction boxes is easier when breaking off into other rooms. Since all your ground is returning to the common in the circuit breaker box you shouldn't have a problem. Im using 3 separate breakers for my studio. 1 for lights, one for audio items and the other for accessories like drum machines, lava lamps, christmas lights, degausser and recorders. I don't have any problems with this set up.

SoMm

 

[Michael Jones]

Yeah.
Man. I was majorly confused on this point once too.
From what I understand, taking a ground from outlet, to outlet, to outlet, and then to the main ground is NOT the way to go. Doing that could induce a ground loop.
What I understand, is that you'd want to take EACH outlet to the main ground.

 

[LDQ]

Yeah.
Man. I was majorly confused on this point once too.
From what I understand, taking a ground from outlet, to outlet, to outlet, and then to the main ground is NOT the way to go. Doing that could induce a ground loop.
What I understand, is that you'd want to take EACH outlet to the main ground.

Michael,

This is what I don't get....I would think that even if you connect the grounds from outlet to outlet in series then connect to the main ground...such as option 2 in my drawings...all outlets will have a common ground anyways...I would think the only difference will be the cable distance from the ground of each outlet to the main ground. I don't know if that is a problem.


Son of mixerman,

Are you saying that option 2 is correct? Michael seems to think that option 2 is wrong....Now I am really confused...am I missing something here.

Cheers,

Luis.

 

[Michael Jones]

Michael,

This is what I don't get....I would think that even if you connect the grounds from outlet to outlet in series then connect to the main ground...such as option 2 in my drawings...all outlets will have a common ground anyways...I would think the only difference will be the cable distance from the ground of each outlet to the main ground. I don't know if that is a problem.

OK, lets say you have 4 outlets in a series. Like in your diagram, option 2, for the control room.
Let's say the ground connection from outlet 2 comes loose. (Or looses contact, or wasn't really grounded well to start with.)
Because they are in a series, each one past the loose connection (outlets 3 and 4) are no longer grounded. But your equipment is. What ever is plugged into 3 and 4 starts searching for a ground; over and over and over. It loops. It hums.
See, that's why you can lift the ground on your equipment (NEVER a good idea, don't do it!!!) and eliminate the hum.


If I'm wrong, someone please knock me upside the head!

 

[John Sayers]

Luis - star earthing should work like this:

Cheers
JOhn

 

[LDQ]

OK, lets say you have 4 outlets in a series. Like in your diagram, option 2, for the control room.
Let's say the ground connection from outlet 2 comes loose. (Or looses contact, or wasn't really grounded well to start with.)
Because they are in a series, each one past the loose connection (outlets 3 and 4) are no longer grounded. But your equipment is. What ever is plugged into 3 and 4 starts searching for a ground; over and over and over. It loops. It hums.
See, that's why you can lift the ground on your equipment (NEVER a good idea, don't do it!!!) and eliminate the hum.


If I'm wrong, someone please knock me upside the head!

Ok I see what you mean....but ideally if nothing comes out loose and all connections have good contacts it shouldn't hum right?

 

[Michael Jones]

Well, yeah, ideally.
But things happen.

Thanks John, I was JUST going to revise his drawing like you did.

 

[LDQ]

Luis - star earthing should work like this:

Cheers
JOhn

Got it...I guess I need a separate ground cable for each outlet. Ouch!!!...that sounds like a lot of work.

Thanks John,

Luis.

 

[Son of Mixerman]

I don't think that Micheal is saying that Option 2 is wrong, or that option 1 is wrong, what he is saying that potentially a ground loop hum could occur in both of those schemes if one of the outlets fails to complete the ground and it leaves averything down stream lost. (I could be wrong too) Number one will effect more outlets depending on where the grounds gets dropped.
The potential is there, buy using proper tool you can check the outlet for polarity and ground funtionality and fix it if something has gone wrong.

Star Grounding will work if your entire house or facility doesn't already have a main breaker panel. You don't have to always use a star grounding technique. It all depends on where you live and what codes have been used in building your home or studio. Most main breaker panels have a main bus bar where all the grounds come together as part of residential building codes. My old house was 2 core wire with no grounds provided at the outlet so a Star grounding scheme had to be done when I built the studio. My current studio has a bus bar for grounds and I run one breaker into a juction box and all by grounds terminate there to the main ground wire from the bus bar. I have no humming from grounding problems. Some places still have 2 wire because of their age and there you would have to go to the ground star. Most of the things used in a studio with older vintage stuff now use star grounding og the internal components.
The reason I go the way I do, is that tracing and routing a main ground bundle is easier and I when I debug problems I can isolate by outlet and then by junction box without having to pop open the main breaker and start fidling in the dark. Also the main ground bundle might to big in diameter if you have alot of outlets and then you might have to weld the ends together. If for some reason you need to add an outlet at some point, you have can't pull out the grounding bundle now. Just my 2 cents, it depends on what you need.

SoMm

 

[Michael Jones]

I don't think that Micheal is saying that Option 2 is wrong, or that option 1 is wrong, what he is saying that potentially a ground loop hum could occur in both of those schemes if one of the outlets fails to complete the ground and it leaves averything down stream lost. (I could be wrong too) ... SoMm

No. you're right.
Option 2 would certianly meet code in my city.
But the potential for ground hum exists there.
More so in option one.
If the idea is to ELIMINATE the POSSIBILITY of ground loop hums, then star grounding is the way to go.

 

[John Sayers]

What you are saying, Craig, is run a separate 3 core feed to each outlet individually?? That's what we did at left bank - no grounding probs

cheers
john

 

[Gunther]

c7sus

Wiring like you said sounds a little overkill to me. If there is a reliability issue with the receptacle down the road then he can easily pull it out of the wall and replace it.

But if you want to go overkill, be sure to use hospital grade receptacles. They never lose their retention and always make good contact… but overkill IMO.

And IMO if the ground wire is properly installed its overkill to run a ground line to the box for each receptacle. Just do the job right and there should be no ground loop issues.