electrical phase

Glen, I have three phase as pointed out in my post, it is 120 / 240 as I mentioned already.

My comments are correct for my particular configuration and did explain that there are two supplies coming into my home. Are you saying that in most home electrical drops the panel does not get power from two different 120 volt supplies?

I have two panels in my utility drop closet. One three phase that runs the AC and one that does not contain the third leg, that has two 120 volt AC drops.

Inside the house is three panels, two are 100 amp Square D and both have two different voltages supplying them (they always meter differently).

The third panel is 220 only, and the two hot legs measure the same as each of the 120 Volt supplies.

The power coming in is a four line double zero cable, and a 750 amp box with a amprobe type meter (pull the meter, the power stays on).

Albert,
Your 3-phase power is probably 120/208. My guess is your reading 120v phase to ground, but if you put a good meter phase to phase it probably reads in the neighborhood of 208v. Check it with a high-grade meter (Fluke) sometime. This is a typical 3-phase voltage used in the USA no matter where you live.

If your reading 240v phase to phase then you probably have 120/240 with a high leg. That means one of your legs will be reading 277v phase to ground. I doubt you have this kind of power in a residential neighborhood.

In a typical residental service the panel does derive power from two separate 120v supply lines, but the supplying transformer is a single-phase transformer capable of producing 240volts. (This does not apply to you)

It does not take two transformers to produce 120/240

And without two or three transformers you cannot get two phase (No such thing) or three-phase power.

If Memory serves the transformer on the pole has a center tap (Neutral/ground), which allows for a reference point on either leg. Thus there are not two phases present just two hot's and one Neutral (Ground reference) derived from one transformer (One phase of a three phase system) on the pole

Hot to hot reading 240v
Hot to neutral reading 120v (when grounded to earth)
(Again this does not apply to you)

Your house has one main drop three phase derived from three single phase transformers on a pole or in an underground vault near by. These three transformers are configured to produce the desired voltage you seek which is typically 120/208 based on what you've told me already. This is in fact your main power at your main panel. 120/208 three phase.

From that three phase panel two hots and a neutral are sent to a single-phase panel (in the same closet). Even though we typically refer to this panel as single phase (Standard terminology) you are in fact feeding it with two phases. (ONLY BECAUSE YOU HAD 3 PHASES TO START WITH) This is a little different than a normal residential installation and in fact would be treated as a commercial installation.

Let's talk about the reason the two panels inside your house have different voltages. They are 120/240 panels which means you are using *A phase* and *B phase* tapped from your main three phase panel to feed one. *B phase* and *C phase* tapped from your main 3 phase panel to feed the other. You see that each panel has at least one different phase than the other. That's why the voltage reading is never the same at both panels.

It would be a little hard for me to believe that you’re only reading 120 phase to phase at these panels. You should be reading 208 phase to phase. There is no way an electrical contractor would do this type of installation unless he doubled the size of the supply neutral, you would also have to run a dedicated neutral with every hot comming out of the panel.

As for your meter That's called a CT meter (Current transformer) when you pull the meter you do not disconnect the line power, just the ct's. Pretty common in Commercial installations.

I am reading 241 Volts phase to phase with a Fluke 2860 A. Phase to ground is 120 on each leg.

On the topic of this thread. Would audiophiles not benefit from my suggestion of keeping one of the two 120 volt supplies as the primary power for the stereo and the noisy stuff on the other?

Other than the confusion about the set up of the breakers in the box and the fact that I have 3 phase, it seems the two 120 volt supplies most readers (probably) have could still benefit from Killerpiglets idea of separate runs.

Also, why could everyone not use a meter to differentiate between the two 120 volt drops? I do this often behind my equipment. I just meter several plugs, and the one that is the low leg gets the digital equipment, as I keep it on the opposite run from the analog gear.

I would be surprised if two runs coming in were EXACTLY the same voltage, and this would be an easy way to tell them apart. It always works here, the voltage may change a little during peak usage periods, but the two supplies stay almost the exact number of volts apart, day or night.

Albert,

Are you reading all three phases 120v to ground?

Albert,

There's no way to separate a 2-pole 220v breaker to one side or the other. I think we all know that? No matter what you do the noise from your 220 circuits will always be present on either side of the panel.

You could in theory separate all your 110v breakers to one leg of the panel, but that's not necessarily a great idea.

The main objective when terminating a panel is "load balancing" That is to say an equal amount of amps on each side. This will reduce the load on the neutral conductor. When you have 50amps on one leg and 50 amps on the other there is zero amps on the neutral.

However if you had 100 amps on one leg and 10 amps on the other you would have 90 amps on the neutral (Grounded conductor) This poses some serious concerns. Electricians and engineers always seek to reduce the load on the neutral by distributing the load equally to both sides of a panel. The same holds true in three-phase power distribution.

You may also want to consider labeling your outlets with a P-touch labeler. You could mark the phase (A, B or C) plus the circuit number and panel designation. That may come in handy when moving things around.

Take care

Balancing the panel= Best installation