Electrical question (home wireing)

[Richard]

Scenario: I'm finishing a room downstairs and will be moving my electronics down there (stereo/tv...)

I've been told that sometimes, one factor in getting ground loop hums in a stereo system is different components being plugged into different circuits (different plugs leading to different breakers in the panel box)

True, not true... I dunno.

So... in light of that and actually, irrelevant to that situation, I ask is the following a known breach of code?

If you have a panel box in the garage and want to run say, three outlets to your stereo room. One on the left wall, one on the back wall and one on the right wall. Each outlet is a SINGLE outlet on its OWN breaker at the box. They are not daisy-chained on the same circuit.

So, you have three different runs from the box to each outlet location and this run will be 12-2 wire w/g.

Fine/dandy.

Here's the question.....

Is there any benefit or more importantly, breach of code, if you went to box 1 and attached a SECOND ground wire and ran it through the walls to outlet #2 and then to outlet #3?

So, each outlet has a single 12/2wg wire from outlet to panel box and a SECOND ground wire going from box to box such that each box is tied to the next?

This way, if they have 50' of wire for each hot run, they might instead have 10/15' of distance before they find a common ground with each other.

If it's over kill or stupid...that's one thing.... if it's dangerous for some reason, that's another and why I'm asking.

btw, my BIL is an electician and will be doing all the hooking up, I'm just preparing to do all the grunt work and pull the wires through the walls.

 

[Aguanga]

Let me prequalify stating I'm not an electrician, but have had a good amount of experience. It sounds like overkill to me. What are the power requirements of your equipment and future needs that will require a separate breaker for each outlet? What size breakers were you going to install? 14-2 is usually sufficient for a 15 circuit, but it is always a good idea to run with the 20 amps and heavier guage wire (12-2) if you can afford it. The grounds looped between the outlets on separate circuits sounds redundant to me. Inside your panel and you'll notice that all of your circuits share a common ground which is also shared with your neutrals. I have not heard of the ground hum thing before... If it was due to different circuits, maybe it actually has something to do with the circuits being on different phases.

 

[RobS]

I will preface by stating my lack of knowledge...

I do know that we have some very sensitive equipment at work. Some of it runs on "clean power", through some sort of conditioning unit. I know nothing of these things, only recall our EE lab talking about it one day...

 

[Shimon]

Don't bother. What you are doing is installing three circuits which are independent of each other and are using isolated grounds. Leave them isolated so they can all reach ground independently and faults won't be transmitted through all the circuits...any ground fault will go directly to the main box and then the ground wire. There's no reason for their grounds need to "see" other. If you hook the grounds all together then you are defeating the benefits of having isolated grounds. Some claim isolated grounds also reduce noise traveling on the ground line but that's questionable.

 

[mohrds]

Ground wire is relativly useless as most electronincs are polorized 2 prong plugs other than big TVs.

The neutural is the usual culprit. In 110V household wiring, there is no negative wire. Just one hot and 1,2, or 3 ground wires. All the Neutural/ground wires are electrically equal other than the path they take.

Often, two circuits share a single ground wire which is perfectly safe and code compliant (if using different legs of the hot), however it can contribute to the hum you are referring to.

Since you are doing home runs with a single hot and a single neutual to each outlet, you will not have any problems. Whether you bond all the grounds together or not is not relevant.

However, bonding the elctronics cases together with a solid copper wire will help to eliminate the hum. Most high-end gear has lugs on the case specifically for the bonding wire to tie them all together.

Now, as someone who has done a lot of AV installs, I highly reccomend just running a single 20Amp circuit to a single outlet and use a single power conditioner to feed all the equipment.

I have seen some impressive setups with projectors, subs, extra monitors that never draw more than a single 15 amp circuit can provide.

Also, instead of a brand name power conditioner, I always just get a used APC Smart UPS from Ebay and buy a new battery. Full power conditioning, plus a battery for if the power sags. You can usually get one from Ebay cheaper than buying a power conditioner from the AV store.

 

[Mike058]

Check out this site Ground loop problems and how to get rid of them - On this page Methods for breaking ground loop it suggests just what you're describing. The big difference is it says to run a heavy grounding wire between the cases of the components rather than the outlets. That's not dangerous, just not worth doing.

 

[Richard]

Now, as someone who has done a lot of AV installs, I highly reccomend just running a single 20Amp circuit to a single outlet and use a single power conditioner to feed all the equipment.

One reason I'm trying to do what I can to preclude the chance of ground loop hum is, I've got some hugely efficient speakers (about 109db) and they will be merciless with any noise in the system at all.

One reason I'm thinking for several decidated lines is, I might take some OTL tube amps (high electrical needs if I understand it correctly) and place the amps near the speakers which will be on the opposite side of the room as the other electronics. (signal sent via balanced XLR cable).

I might never ever use these amps "near" the speakers but if I do, I want to be sure that they've got all the juice they might ever need.

Also....with my current setup as is.... when my wife decides it's time to turn the vacume cleaner on, I will at times, pop my breaker.

Because of that, I want to put some extra outlets in the room.... orange ones (actually, probably gray) for audio uses and normal ivory ones for HER uses (lamps, vacume....torture toys....)

Since I"m doing this essentially myself, I don't mind the extra work and cost of over doing it. I'd rather over do it during stud walls, then to have the room completed and find out I could have done something differently and possibly avoided an issue.

hum can be a real bugger to track down. I figured bonding the grounds on the outlets was a good idea....

I didn't realize that the bonding of the grounds was better done on the equipment end of the wire!

 

[radioman]

I am not a certified electricain either but having done a few wiring myself I dont see why you cant have a single decidated service 15 to 20 amp breaker from panel to your new basement area. What ever you are finishing off in the basement, I would put a new line for plugs on new finished part of your basement. Your lights could be tied into your old line to eliminate any overloading, introduction of line noise on your high end equipment. As Mohrds stated, use a UPS batery backup for line conditioning of your sensistive equipment. The company I used to work at used them all the time on servers before they upgraded to a large unit for whole room. This should be the cost efffective way of wiring your basement.

 

[aczlan]

One reason I'm trying to do what I can to preclude the chance of ground loop hum is, I've got some hugely efficient speakers (about 109db) and they will be merciless with any noise in the system at all.

One reason I'm thinking for several decidated lines is, I might take some OTL tube amps (high electrical needs if I understand it correctly) and place the amps near the speakers which will be on the opposite side of the room as the other electronics. (signal sent via balanced XLR cable).

I might never ever use these amps "near" the speakers but if I do, I want to be sure that they've got all the juice they might ever need

how much power will these amps be pulling? you may be able to fit them all on a 20a circuit, if not (and you find hum to be a problem) you can run the XLR cables through a ground lift/DI box to eliminate hum.

Aaron Z

 

[mbohuntr]

I'm NOT an electrician!!!, you could be picking up something from flourescent lights, or stray radio/cordless signals. I watched a fellow set up an oscilloscope to find out what frequency your hearing, then purchase a inline filter.