Dedicated Circuits - To All Users Of (1 Viewer)

[brucek]

Ron,

I hope it's safe too.

Safer - yes....
You are using a GFI in an ungrounded condition. It is safer than a normal receptacle used in an ungrounded (cheated) condition.
When a normal outlet is wired properly, and a three wire device is plugged into it, the metal case of the device is now attached directly to your house safety ground system. If a short occurs internally in the device and the case becomes live, then the breaker for that circuit will immediately trip indicating the fault. If you have the third safety wire cheated or removed and this happens, the live metal case will likely electocute you because the breaker won't trip. The 120volts will travel through you if you touch a ground. That's obviously bad news.
What happens when you use an ungrounded GFI? Well, when a fault occurs in the device, the case again becomes live. There is no "difference" in the loads at the GFI so it doesn't trip yet. When you touch the live case, the hot current exceeds the neutral current and the GFI trips. See the small problem you still have. You don't get electrocuted, but you get a shock. How bad a shock is determined by the speed of the GFI.
You're safer - not safe.........
brucek

 

[Ron Duca]

brucek,

So, do they make any kind of device that will allow me to use a standard grounded outlet, but will filter out the static and other electrical crap? I want the same sonic results I achieve by removing the ground, but with the safety of using the house's earth ground.

I'm sure they make something that will sound almost 1/4 as good and it will only cost $4,386.19. Right?

Ron

 

[Wayne A. Pflughaupt]

Ron,

He tried several things trying to eliminate the interference, including creating a separate ground of some sort for the circuit feeding my living room outlets.

You might try doing this optimally, not “jury-rigged” as the electrician did. It is known as an “isolated ground circuit.” The grounds from your dedicated circuits would go to a new ground stake that would be driven specifically for these circuits. The new ground stake would be connected to the main stake with a heavy-gauge wire, like 8-6ga., in keeping with code requirements.

The idea is that the equipment on the dedicated line would be properly grounded, while isolating it from all the “hash” coming to ground from the other circuits. I know this is often done in commercial applications where sensitive equipment is used (like computer mainframes or in hospitals). I’d be interested to see what brucek has to say about the merits of using IGs in a home theater.

Aside from that we’re really beating a dead horse at this point, Ron. Brucek has iterated in great detail on this thread and the other one I linked the benefits of installing a dedicated circuit. That is the best chance of eliminating this problem. Everything else is a “band-aid” approach.

Regards,

Wayne A. Pflughaupt

 

[Wayne A. Pflughaupt]

Brucek,

Since we’re on the subject, I’m hoping you can answer a burning question:

When a normal outlet is wired properly, and a three wire device is plugged into it, the metal case of the device is now attached directly to your house safety ground system. If a short occurs internally in the device and the case becomes live, then the breaker for that circuit will immediately trip indicating the fault. If you have the third safety wire cheated or removed and this happens, the live metal case will likely electrocute you because the breaker won't trip.

I fully understand why the ground is there and how it functions. What I don’t get is why some equipment has a grounded plug and some does not. I can see for some things like a TV that has a plastic case that a ground would not be needed. But most electronics in a HT system have a metal chassis, or at least a metal cover. Why do they have ungrounded plugs?

Regards,

Wayne A. Pflughaupt

 

[Ron Duca]

The electrician explained that if he did drive a separate ground stake into the ground, he would still have to connect it back to the main ground somehow. I'm not completely stupid, as far as you know, but wouldn't that just cause the new ground to pick of stuff from the existing one? I didn't pursue that option because I didn't think it would work, especially after he tried a semi-separate ground.

Is this something I can do? I'm not a certified electrician, but I do understand quite a bit of this stuff. I have installed outlets, switches, ceiling fans, run wire, etc. I would pay another electrician to come do it if I knew for a fact it would resolve my problem. Paying someone for their guesses gets pretty expensive.

Ron

 

[brucek]

Wayne,

I would think creating a separate isolated grounding system for your home might be a bit extreme. An isolated grounding system is essential in a commercial building where a lot of heavy equipment is use in conjunction with sensitive equipment.

I know you already know this, but others may be interested. Unlike a normal receptacle used in the home, an isolated receptacle has no connection between the third prong and its metal case. In a buildng where these are used, they run three wire cable instead of two wire. The three insulated wires are hot, neutral, and ground. Then the bare wire or metal conduit, known as the building ground, connects to the metal case the receptacle is housed in. The green insulated wire is connected to the third prong and is then isolated from the "dirty" building case ground which takes on a rather noisy signature because of heavy equipment etc and specifically because the cable is usually run in metal grounded conduit that fills the building.

The green isolated wires are all star connected to a central point where they finally bond to the earth along with the building ground. This allows the third prong of sensitive equipment to be isolated from the buildings ground.

Simply using isolated receptacles in the home would be rather ineffectual unless you ran three wire + bare wire circuits to your dedicated boxes and created a separate isolated ground system that you then bonded to the houses safety system. As you outlined in your post, I guess if you did this it would be effective. This is done usually in studios, but in a simple home, the cable distances are short, there isn't any heavy equipment and it is fairly easy to run a couple dedicated circuits using the normal safety ground under conditions where you decide the path and the cable lengths and locations of boxes. Maybe it would be effective in Ron's case though, as you suggest, but he'd have to run new three wire cable for his dedicated circuits and install a ground rod etc, etc. I suggect he go the balanced power route instead.

When a device has a two prong plug, then the case and all external parts are double insulated from the circuits inside. Very little chance the case will become hot.

Ron,

The electrician explained that if he did drive a separate ground stake into the ground, he would still have to connect it back to the main ground somehow. I'm not completely stupid, as far as you know, but wouldn't that just cause the new ground to pick of stuff from the existing one?

Yes, the two ground systems must be bonded at a single point eventually, but the coupling of noise from one ground system to another doesn't occur or at least is heavily attenuated because of the impedance to ground of each system itself. The noise from one system (because of it's lower source impedance path) would rather travel to earth ground than try and travel into the other grounding system. This creates an isolation. You have to realize that a length of wire is not a dead short, every wire exhibits resistance that compounds with length.

brucek

 

[Ron Duca]

OK. I looked at my service panel again and even popped out a few circuit breakers. Here's what I found. My service panel has 20 numbered "sections" and each of those has an A and a B circuit breaker, except for a couple of double breakers that feed the range. Sections 1, 3, 5...19 are on the left and 2, 4, 6...20 are on the right. The legs, or phases as I understand it, zig zag so that on each side, every other numbered pair of breakers is on a different leg. In other words, the breakers in 1A & 1B are on the same phase as 5A & 5B and 9A & 9B, etc. The same applies for the even numbered pairs of breakers on the right.

The outlets in my living room, which feed my audio/video system, are on breaker 9B. The lights in my living room are on breaker 11A. These are separate circuits and different phases. From what I've read, that should be OK. However, the house is wired using 12-3 with a ground. Each set of wires coming into the service panel contains a red, black, white and bare wire (ground). The black wire that feeds my outlets (9B) and the red wire that feeds the living room lights (11A) are in the same "run" of wires. The wiring is the same throughout the house and I don't know of any way to separate those.

Riddle me this though...If I could find where the connections are made to the first living room outlet or light switch, couldn't I disable one of those connections and run a separate 12-2 with ground to that point? Wouldn't that totally separate the two circuits?

Ron

 

[brucek]

Ron,

Aha, the riddle is solved. This is a standard trick to allow the contractor to run less cable. You're allowed to run three wire cable (two hots and a neutral), and hook the two hots to opposite legs. This gives you two separate circuits in the same cable "sharing" a single neutral. Now you ask, how can that be, won't the neutral be carrying twice the current and be overloaded. Nope, because the two hots are 180 degrees out of phase.

Having the two hot legs in the same cable side by side will be giving you the grief on your safety ground at your HT. I'm afraid you can't really separate these. You can't put the same leg on both hots, because the neutral would be carrying too much current.

I'm afraid you'll have to find a way to run a separate dedicated circuit to your HT.....

brucek

 

[Wayne A. Pflughaupt]

brucek,

Thanks for the comments on IG circuits and components with ungrounded plugs (I’m rather surprised the answer to the latter was so simple!). I was sure you would be able to shed some light.

Ron,

brucek noted the potential ground situation with dual hot legs sharing a cable. However, in your case the problem will be even worse since the light circuit has dimmers on it. As brucek noted earlier in the thread:

I would pay another electrician to come do it if I knew for a fact it would resolve my problem. Paying someone for their guesses gets pretty expensive.

I think it’s safe to say at this point a dedicated circuit is virtually a risk-free solution to eliminate the noise in your system, since it would physically separate your HT wiring from the problematic lighting circuit.

Regards,

Wayne A. Pflughaupt

 

[Ron Duca]

I thought for sure I could solve this problem, but I'm afraid I've tried everything I can. It's not that I don't want to run a dedicated circuit. The way the house/room/wall where the equipment is located is designed, it's inaccessible from the attic. The only way to get wire in the wall and up into the attic is to cut a hole or two in the wall/ceiling in my living room. The wife and I don't believe we want to do that in our less than one year old house at this time.

Anyway, just to see if it would help, I connected some 12-2 w/ground to the only spare breaker in the service panel and ran it into the house. Yes, through the garage, utility room, hall and into the living room. I connected the other end to a grounded outlet and screwed it into a plastic outlet box and put an outlet cover over it, for safety. For all practical purposes I had a dedicated circuit. I plugged in my equipment, and it was just slightly better than using any of the grounded outlets already present. The buzz/static was back and so were the ticking sounds I was getting when flipping light switches in the living and adjacent rooms.

The bottom line is that the interference is unacceptable and so it the thought of an ungrounded outlet. I may check into finding an amp that is internally grounded (uses a two prong power cord). I believe Outlaw makes one. Does anyone know of any others? If I can't find one, or if I do find one and it produces the interference also, I'll just upgrade my current receiver.

Thanks to all who have provided input for this issue. All of your input has been valuable and quite educational.

Ron

 

[brucek]

Good test Ron. I'm surprised at the results, but there it is anyway.

I guess you don't want to consider a balanced power unit like I originally suggested? Maybe some store can let tyou test one..

brucek

 

[Ron Duca]

Bruce,

You're not talking about a power conditioner are you? I tried one of Monster's units, the HTS-3600. It had no effect that I could tell.

What brand and models of balanced power units are you familiar with? I would be willing to try one of these. It would have to significantly reduce the interference I receive when having the system properly grounded though.

Thanks,

Ron

 

[brucek]

Ron,
No, I'm not talking about a power conditioner.
A balanced power unit is basically a very high quality isolation transformer with a center tapped low impedance secondary. So instead of a hot of 120 volts and neutral return, you have two 60 volt lines with a center tapped ground. Across the 60 volt lines which are 180degrees out of phase you have your 120 volts, with each 60 volt lead referenced to the ground at the center tap. There are a lot of benefits in this configuration. Any reactive currents developed in the load arrive at the common center tap and are cancelled. Any noise that would normally travel on the safety ground are cancelled at the center tap. There's not much chance of a ground loop.The other benefit can be a lower noise floor.
I think this could be a good solution in your case. A 15amp unit is around $900. Maybe visit the Link Removed site and see what you think.....
brucek