John Sayers' Recording Studio Design Forum Archive

EDITED!!!!!


Greetings!

Know this for SURE...I am NOT an Electrician, but I'm trying to
understand the process for my Star Grounding...

I'm having an Electrician to come over to give me a quote for installing my wiring etc. I was reading some posts on here and Googled in info on IG receptacles. I made a copy of the Star ground diagram in Rod's book to give to the Electrician, but to make sure "HE" does it right I want to make sure "I" know how it's done and can identify with what he's doing. Man-O-Man...I got BURNED with the Electrician that did the wiring for the
rest of my basement ! I depended on his knowledge-expertise...Had to have some of his work RE-DONE! THIS time, I WANNA know for myself!!

I read here...
http://www.johnlsayers.com/phpBB2/viewtopic.php?t=3950
that you could use Romex wiring with an IG receptacle instead of having to use conduit.

In trying to "plan ahead", I wanted to have receptacle power on-off switches (only for the receptacles that power my main equipment) to allow me to turn my equipment on or off in "groups" so I don't have to turn "everything" on when I only want to listen to a CD or pump cable music channels through my speaker system. (In these cases all I would need power for would be the CD player, my power amp to my speakers, my cable digital box etc etc.) Also, I wanted to allow enough receptacles/amps for future equipment purchases.

Here is my understanding/idea as to how this should be done...

Presently, I have an additional breaker box that was installed mainly for my Studio, but also for additional breakers needed for my finished basement. (See attatched pic) I plan to have 2 new ground rods installed outside the house and the ground wire (#2 or #4 AWG) sent to a common ground bar in what I'll call my "Star Ground" panel box next to the breaker panel. This box will only be used to connect Isolated Grounds to each individual IG receptacle.

Because I want to have receptacles to my main equipment switched on and off as stated, I plan to run Romex (NM cable) 12/2G cable from a 20 amp breaker in my breaker panel to a regular switch then to 2 "daisy chained" IG receptacles. (There will be 3 sets of these) This switch would be wired with the hot to the switch and the neutral passing thru the switch (not connected to anything). The (bare) ground is attatched to the switch frame and the switch box. The hot, neutral and bare ground from the switch would all be sent to the first IG receptacle with the hot and neutral wired as normal and the "bare" ground wired to the receptacle (metal) box. One of the Isolated Ground wires (from the Star Ground panel) would be connected to the Isolated Ground connector on the IG receptacle. The hot and neutral would come from the 1st IG recptacle and terminate in the 2nd IG receptacle. The (bare) ground will terminate on the 2nd IG receptacle box. Another Isolated Ground wire (from the Star Ground panel) would be connected to the Isolated Ground connector on the IG receptacle.

See the diagram below for Switched-Star Ground wiring...

If ANY of the previous procedures are incorrect, let me know!

My questions are as follows...

1.) Is there a special type switch I need to use to be able to turn each
receptacle on and off?

2.) What guage/type wire would be best for the IG wiring from the Star
Ground panel?

3.) Is it better having the new ground rods installed or would it be just as
good (possibly even necessary) tapping into the earth ground rod
for my main breaker box as per the drawing/diagram in Rod's
book?

4.) I believe Aaron mentioned you may need an additional ground wire
for the metal receptacle box. Do I have this right? If so, please
explain what this means & is it the "bare" ground in the Romex or the
Isolated Ground that's being refered to?

5.) Is there an advantage to running the receptacle wiring in conduit
compared to using Romex wire cable? (Advantages besides rodent
protection & ease of running additional (new) wiring in the conduit)
Is conduit better for RFI reduction?

6.) I've read this quote in a post...
"Keep in mind in a subpanel that the neutral bus has to be isolated
from the ground bus and panel. The ground and neutral are kept
isolated untill they bond in the main panel". Does this have an effect
with the procedures I need to follow to "Star Ground" my receptacles?


Well, that's it...
Thanx for any/all help!

The post above has been edited...
Anyone got any thoughts on this????

Unless I missed something, I think you have it covered - the bare (included) ground with the romex would be your "safety" ground, connected to boxes ONLY. Your receptacle frames should contact the metal box (called "bonded") so they will already be at safety ground potential - it won't hurt to add a physical wire between box and outlet frame, but not necessary.

Your isolated grounds can be run with insulated wire, preferably green but it's allowable to "tape" both ends green.

If your sub panel is in the same building with the main system, it's not necessary to drive separate ground rods - it's not even desirable. Just bring your ground wire from main panel into the sub and bond it to the ground bus in the sub panel.

This sub panel ground bar is the ideal place for your "star point" - just return each and every IG receptacle's green ground wire to that bus bar. The point here is for every 120 volt source to have only ONE point ground, and that must be a "home run" to the SAME point for every receptacle - that way, there is only one reference for ground and NO WAY for ground current to run between any two receptacles - no current = no noise.

If you use conduit, it will be bonded to ground at some point along the way, typically at the sub panel - but if you do this AND connect a WIRE for safety ground, it's possible to get a loop. Normal conduit runs (IIRC) only have a wire from a bonding screw in each box to the receptacle frame to avoid loops.

Again, the whole point is to have NO LOOPS - which is why we use home runs from each receptacle to a COMMON point and nowhere else... Steve