Do I get a thumbs up on this?

Eggman · Post by **Eggman** » Thu Jan 12, 2006 7:08 am

I am ready to do the AC wiring in my two room studio and just want to double check my plan.

I want to run one 20 amp circuit to each of my two rooms (live room and control room) for the audio. These will be taken from the same leg of my service. From the other leg I will run one circuit to handle all the lighting for both rooms.

Does this seem right?

Do you think I could get away with one circuit shared between both rooms for audio? I have a fairly large analog system and will occasionally have a full band in the live room.

I have a star grounding question. I think I understand how to wire the outlets and run the ground. My main panel is grounded to the water pipes. Should I sink a grounding rod and run my star ground to that instead. Since the neutral is connected to the water pipe ground back at the box will this be a problem?

Thanks in advance. I have been working on my studio for almost two years and finally see the end somewhere in the near future. I will post pictures one day soon.

Thanks again,

Doug

knightfly · Post by **knightfly** » Thu Jan 12, 2006 11:02 pm

Star ground doesn't mean a SEPARATE ground, only that ALL outlets get their ground (third pin) from EXACTLY the same PART of your ground system - just connect each outlet's ground (assuming NO conduit, but Romex wiring instead) to the ground bar in your panel, and NOT to each other (no daisy-chaining of grounds)

I would do as you said and put two separate circuits on the same leg; no telling how big the amps, etc, might be for a full band... Steve

Eggman · Post by **Eggman** » Tue Jan 31, 2006 10:18 am

Thanks for the info. I think I am clear on the basics of star grounding.

I used steel studs when building my walls. After talking with a Seattle electrical inspector yesterday, I decided the best way to go was to run 12-3 romex that I already have, as opposed to running THHN through conduit. I will make a home run from every two outlets using the bare wire and the third wire as grounds.

I have some questions.

1. Where can I find grommets to run the romex through the prepunched holes in the studs (3/4")? I've looked everywhere in the area and on the internet. Who makes them?

2. I have a bunch of IGRs. I plan on using plastic boxes. I will run a seperate ground from each outlet back to my star grounding point. Are the IGRs Ok to use? Do I have to run another ground from the body of the each outlet in addition to the SG? Do I gain anything from using IGRs with plastic boxes/romex? Will I get the same results using regular cheap outlets?

Feb will make two years of studio building. I hope to finish by this summer. My wife is a patient patient person.

As usual, thanks for all the help and answers.

Doug

knightfly · Post by **knightfly** » Tue Jan 31, 2006 11:12 am

Have you tried the same place you got the steel studs? What brand are they? If they're Dietrich, here's the catalog for part #'s, etc -

http://www.dietrichindustries.com/produ ... ntro06.pdf

It's wierd, but I get totally different search results using Earthlink's embedded google instead of first going to the actual google page -

http://search.earthlink.net/search?q=st ... narrowband

Have you tried local drywallers? I can't believe they wouldn't have those, how would you wire a house without them??!?

HTH... Steve

Eggman · Post by **Eggman** » Tue Jan 31, 2006 11:51 am

Thanks Steve.

I will try and locate some, now that I have a product to ask for.

What are your thoughts on question 2 from above concerning the use of Isolated Ground Receptacles?

Post by **Aaronw** » Wed Feb 01, 2006 12:35 am

I found the grommets at Home Depot here. I'll try and find the bar code number for you. They come in a big ziplock type of bag (yellow PVC).

Also check here on page 37 of 64 http://www.greenlee.com/cat_docs/Holemaking.pdf

knightfly · Post by **knightfly** » Wed Feb 01, 2006 1:33 am

With plastic boxes, no metal conduit and romex wire, IGR's are a waste of $$ - as long as you don't use metal cover plates (tying two ground paths together) the standard outlets are fine for a star system... Steve

Eggman · Post by **Eggman** » Thu Feb 09, 2006 12:36 pm

I got the Dietrich grommets from a local Drywall supplier. Thanks for the info.

I am star grounding my control room w/ romex, plastic boxes and regular outlets, since you say the IGRs would be a waste of time.

I plan to use using Wiremold surfaced mounted conduit and Wiremold boxes in my live room. I am planning a star ground system as well. My question are:

1. Can I/should I use the IGRs with the Wiremold stuff? Or should I again just use regular outlets. I already have the IGRs.

2. If so, do I need to ground the boxes with their own ground (in addition to my star ground from each box)? Like if I was using metal boxes/metal conduit?

As usual, thanks.

Doug

knightfly · Post by **knightfly** » Thu Feb 09, 2006 8:39 pm

IS this a metal wiremold product, or plastic? If plastic, do the same as with the plastic boxes and romex. If metal, you'll need to bond the wiremold and boxes to safety ground, use the IGR's, and run separate grounds home run for each outlet... Steve

edenorchestra · Post by **edenorchestra** » Fri Feb 10, 2006 5:34 am

Doug,

An IGR ground terminal is insulated from its metal mounting yoke. This means you must connect the grounding terminal directly to an effective fault current path by an insulated equipment grounding conductor.

A normal receptacle connects the mounting yoke to the ground terminal. So if you mount a normal receptacle in a metal box, there is conductivity from the ground terminal to the box. If the box is non-metallic then the ground connection from the yoke goes no where.

What Steve is pointing out is that IF you are using an IGR and you are using any type of METAL wire ways (boxes, wire mold conduit, etc.), then those items would not be grounded as would they be with a standard receptacle and as such would have to be grounded as well. These would for star grounding applications require a path to ground at some point in the wire way “circuit” and then the individual insulated ground from the IGR to the ground back at the service entrance. Bottom line is that they all get a connection to ground, just that the IGR allows you to pick physically where in that path you make the connection.

The whole point of the IGR is applicable when the wire ways are metallic and you want that receptacle not to have its ground connected at the same physical point as its wire ways. If you are using non-metallic wire ways then the point is moot. There is only one path to ground and that is directly at the ground terminal on the receptacle. Provided that the ground conductor is insulated then it cannot touch any other ground conductor on its way to the service entrance. You have thus determined where that connection occurs.

If your wire mold is non-metallic, then the IGR’s are of no use, because you are effectively getting the insulated ground effect at the wire way by default.

Eggman · Post by **Eggman** » Fri Feb 10, 2006 7:49 am

Thank you Steve and Mark. Your answers gave me the info I was looking for. Now I know how I am going to spend my weekend.

And yes, my wiremold is metal (the larger 700 series). I got a mile of it free from the performing arts center where I work and found 20 outlet boxes on ebay for a reasonable price. Now I need to find an inexpensive source for fittings.

Doug