There has been this big debate over to phase or not to phase components together, does it really matter, what science could possibly dictate the benefit of such an arrangement. I have always been a big promoter of all things phased together stay together, not because of the math, but rather year’s personal experience.


For example I am completing a large multi zone project, I had originally instructed the electrician to make sure that all A/V locations would be on the same electrical phase.

I found out last Friday that that turned out not to be the case. This house has 11 displays, 5 of which are plasmas, 1 of which is a DLP Projector, and the rest are LCD. It became apparent very quickly during our first multizone component video tests that something was wrong!. All of the plasmas (plasmas only) had the exact same slow scrolling horizontal lines spaced about 12 inches apart .

I thought about this for a little while and realized that something was interfering with the sync since; if you changed resolutions from say 720P to 480P the lines would increase in scrolling speed.

So from experience I tried the most obvious thing, I ran an extension cord from the main system power outlet direct to the nearest plasma, and bingo the lines disappeared and the image sharpened right up. This tells me that the Electrician put all of the displays the opposite phase from the system equipment, which I will have them fix on Monday.


I have installed many systems that are not on the same phase, and to this day don’t have any problems, I have installed systems that have had weird intermittent problems that were only fixed by correcting the phase, and then I have done many a job as described above that had problems right out of the gate. Some of these problems were improved but not solved by utilizing expensive AC filters and grounding schemes, but ultimately the best fix was simply swapping a couple of wires in the panel.

My recommendation is, if you can, put everything A/V on the same phase despite the catcalls and nay Sayers, It will save you trouble in the long run.

I don't know who the nay-sayers are, but you are correct.
First, though, let me correct your terminology. Since a typical residence is "Single Phase", there is no other phase to put the circuits on. The correct term is "leg".
A 120/240 volt single-phase service is derived from a center-tapped transformer. The center tap is the leg that is grounded and often (incorrectly) called the neutral. It is only "neutral" when it carries no current. This rarely happens as this conductor is often carrying the unbalanced load current. The other two conductors carry 240 volts between them and each one individually carries 120 volts to the grounded conductor (neutral).

For some more terminology:
The Neutral wire is the GrounDED conductor.
It is made so by the GrounDING conductor which connects to the GrounDING Electrode System. (Ground rod, water pipe, building steel, foundation rebar etc) (It is at this point where the CATV/SAT/Telco/Alarm etc. needs to be grounded. You wouldn't believe how many problems this will solve!)
The Green or Bare wire running to the outlets is the Equipment GrounDING conductor, but the newer, better terminology is Equipment BONDING Conductor.

For those of you with a good electronics background, and to illustrate what RTI Installer is talking about, draw out a schematic of a center tapped transformer, ground the center tap, and wire two circuits with each circuit originating from opposite ends of the windings and with both circuits ending at the center tap. Put a resistance of 100 ohms on one circuit and 500 ohms on the other. Kirchoff's Law will tell you that there is MORE current traveling through one circuit than the other and that the DIFFERENCE between these two currents is traveling through the grounded center tap.
If you change both circuits so they have the SAME resistance, there will be NO current, Zero Amps, traveling back to the grounded center tap.

So, unless you are using power conditioners on everything, be sure to request that the electrician puts all of the A/V circuits on the same "leg", which on a typical single-phase breaker panel is every other breaker. Also, and this part is VERY important, if you request, say, two 20 amp circuits to one equipment rack, not only ask for the circuits to be on the same "leg", but demand that he runs two 12/2 with ground cables and NOT a 12/3 with ground. (which is what he'll want to do). The ONLY way you can run a 12/3 with ground for two circuits is to put each circuit on the opposite leg from the other. If a 12/3 circuit has the two circuits connected to the same "leg", you will overload the grounded (neutral) wire and burn down the client's house. Look at the paragraph above and you'll see why. The cable manufacturers have, not too long ago, started selling 12/4 with ground. This is a great solution.

But really you guys, you should be running a Romex to your display locations from the equipment rack so it gets plugged into the same Furman/Panamax/Surgex/Monster/InsertFavoriteBrandHere unit as the rest of the equipment in the rack.

I think Larry Fine has made available a wall plate solution that confirms to the NEC and is much cheaper than the Panamax unit.

Great posts guys. I run into the same thing all the time, and more than one electrician has told me he'd phase everyhing together only to not actually do it some reason or other. I've even had an electrician tell me he'd run two phases/circuits to a head end and caught him running 12/3. I think he just didn't think I'd know or didn't believe that it mattered even though I told him it did.

I run into this all the time, and david made a great point about running electrical circuits back to head ends so all equipment will be on the same power circuits and conditioners. We do that for full theaters, but can't do it with multi building monster homes. Good to know though and a great point to reiterate to all us CI's regularly.

This is why I love this site. Thanks to all the invaluable info. I just hope I can contribute my 2 cents worth in a posititve manner as well.

Where is this wall plate solution from larry? I have wondered how to connect all the romex to the eq rack conditioner.

[Link: integrationpros.com]

david, you might be right according to some book, but


Commonly called, by electricians and engineers alike, "phase." There is nothing about the word "leg" to distinguish one "leg" from the other "leg," but since the two "legs" we are talking about (we are not talking about the "leg" called the neutral)(yes, it's called the "neutral" out here in the world) are out of phase with one another, it is useful to refer to them as the two phases of the residential service. See, "residential service" itself defines this as a single-phase service, so the other terms fall under that definition and their meanings do too.


No, it's not. It's called the "ground." The "ground bars" are connected to it, too.


True, but we aren't asking if it is carrying current, we are wondering which color wire to use (again, we are out here in the world); we are also wondering if we are likely to get a nasty shock from it if we happen to touch it.


I thought you said



Glad to see you now think it is called the neutral, 'cause it is.


Does the proper terminology require us to capitalize all DEDs and DINGs?


Power conditioners will not always make this unnecessary, thus it is best always done. We should do what always works, not do what will sometimes and unpredictably cause us to lose time ( = money) troubleshooting and fixing.


GREAT POINT AND TRUE. The breakers are on the hot leads (dare I say "phases"?) and not on the neutral (hey, I thought this wasn't called the neutral ? ? ? ).

Irrespective of what transpires at the street transformer, the reason they can use 3 conductor + ground in the first place is that the red and black conductors never have available current at exactly the same time to return down the "neutral" (often called the return leg, or gounding leg). The red and black conductors are each attached to an opposite hot “leg” in the panel, however neither panel leg A nor B is hot at the same time in their respective alternating cycles, which leads us to the common term “out of phase”

RTI Installer,
this is true only if both legs are drawing the same current. If one leg draws ten amps and one leg draws fifteen, there will be five amps of current from the neutral to the transformer (or the other way, depending on how you look at it).

In fact, one little thing that we make more difficult by properly insisting that all equipment be on the same phase is that the circuits of a house should be assigned to the two different phases in such a way that both phases use as close to the same amount of current as possible to minimize neutral current. The transformer works more efficiently when the two phases are balanced, that is, supplying equal current.

This means that if all the A/V equipment were on the same phase and everything in the house were off except for all of the A/V equipment, there could be fifteen to thirty amps of neutral current.

Larry, is this a problem?

David

Regarding the leg being on every other breaker. Is it correct to assume then that the odd breakers are all on one leg and the evens on the other?

Thanks for the great info.

Rob

Yes, on MOST panels. So, I wouldn't assume. One example is the old Pushmatic brand panels (push on and off rather than toggle). They would have two columns of breakers with the left side on one leg and the right side on the other leg.

Also, there are some GE panels that accept 1/2" wide and/or 1" wide breakers. The size (width) of the breaker, and where the breakers are stabbed into the busbar will determine which leg they end up on.

When in doubt, take the panel cover off. If the breakers in question are all on the same leg you will measure zero volts between them. If they are on opposite legs you will measure 240 volts between them.

Surgex now has a NEMA distribution panel with connection for four 20 amp surge protected branch circuits. I don't have jobs that big but for those that do this could be a good way to keep all the gear on the same leg/phase.

I installed a plasma in my own home. I have a centralized video system. I am most certainly aware of the problem of gound loops due to equipment with a safety gound being connected to circuits on different phases. I most certainly could have run a electrical wire (although I would argue for the superiority of BX over romex, a) encasing the electrical wires in what amounts to conduit helps to limit induction problems and b) that conduit resists screws better than plastic insulation ) but in the rush to get the wires run I forgot. I have very pretty colored lines running from the bottom to the top.

I could move one of the brakers on to the phase of the other, I could run the cable now but I think I shall wait and place the Belkin conditioner in the path and see if it cleans up the issue. If it does without much harm to the signal it will be a welcome additon to solving the problem of video ground loops.

While ground and return paths are electrically the same they most certainly have different resistances. It is indeed the lower resistance of the safety ground, what David has called the equipment bonded conductor, that accounts for the path of this stray voltage to flow to ground.

How many of us specify balancing phases in our contracts or know builders who insist on this? I also think phase is the correct term as it relates to the fact the 120v on each leg is out of phase with the other. Still, an impressive explenation by David. And he's CEDIA certified. Which means he is most certainly smarter than I am.

David and Larry. Soon I may have to stop with the how many electricians does it take to screw in a light bulb jokes.

Alan

I most certainly could have

BX (which is actually a very old trade name from the 1920's and does not appear in the NEC as a recognized cable type. There are two types of this armored cable. Type MC and Type AC) at one time was constructed of steel. Today, when you purchase off the shelf MC or AC cable it will most likely have armor made from aluminum. This will do absolutely nothing to stop induction or EMI. If you can find it with steel armor then it will provide those benefits.

Pretty colored lines means float the ground on the plasma (most of the time anyway)