dhite71 OP149 posts
08-08-2021
6:23pm
I have been thinking more about my 12/3 wire configured for two separate circuits. There is a single neutral and ground wire going back to the panel.
Does this matter when all neutral and ground wires in a house are going back to their same respective bus bar? The neutral and ground bus bars are even connected within the panel.
I would like to understand how two of each returning the panel compare to a single run.
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dhite71 OP ,
You said in an earlier post you did not hear any differences in the before and after installing the 4 new circuits. As a rule that is not what what audiophiles say. Usually they say their system sounded better and well worth the cost of having a dedicated circuit(s) installed.
And then sometimes there will be a post saying that multiple branch circuits caused hum and buzzing from their audio system. Usually the latter is caused from the wrong type of wiring was used and or the wrong wiring installation method(s) was used.
As a rule if the connected load is not all that big, therein say less than 20 amps, it is recommended all dedicated circuits be fed from the same Line, (L), leg, from the electrical panel for audio and or video equipment that is connected together by unbalanced wire interconnects.
(Jmho, it also depends on the design of the audio equipment power supply and how the designer connected the B- and signal ground to the metal chassis of the equipment.
The quality of the power transformer used in the equipment can make a big difference. How well does it control capacitance coupling from the primary winding to the secondary winding(s).
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In most cases the total combined audio equipment ac mains 120V power load is 10 amps continuous or less. The reason given for installing more than one dedicated branch circuit is to decouple the power supplies of the equipment from one another. Especially digital equipment from analog. Something else may be to keep a SMPS(s) away from non SMPS equipment power supplies. With just one branch circuit with everything just plugged into a common power strip there is not any decoupling.
(FWIW, some power conditioners install filtering to isolate receptacle outlets from one another).
With the 3 wire 120/240V multiwire branch circuit, (MWBC), only the unbalanced load, current, of the two 120v circuits to neutral loads return on the shared neutral conductor back to the source. Example, if there is 4 amps on one circuit to shared neutral and 2 amps on the other circuit to shared neutral only 2 amps will return on the neutral conductor to the source. The balanced 120V L1 to neutral and 120V L2 to neutral loads are in series with one another. The two balanced loads are being fed by 240V. (120V respectively measured across each plug/receptacle outlet) That means any digital hash fed back out on the ac Line of the power supply of digital equipment, that is fed from one ac Line, will be in series with a preamp or power amp that is fed from the other ac Line.
Here is a video for you to watch. The guy does a pretty good job of explaining how the secondary winding of a single phase split winding transformer works. (Same way the Utility Power Transformer that feeds your house works).
Look at the wiring on the split phase secondary winding of the transformer as being a 3 wire 120/240V MWBC. Light bulbs represent your audio equipment.
https://www.youtube.com/watch?v=eVamt9IdQd8 //
Even two individual installed 120V dedicated branch circuits that are connected to breakers on opposite Lines, legs, can cause noise problems when unbalanced wire interconnects are used to connect equipment together.
(One branch circuit connected to a single pole breaker on L1 and the other branch circuit connected to a single pole breaker on L2).
Here is an old quote from a White Paper by ExactPower. (The Web Link is no longer any good.
"Less than 300 microamps of ground loop current can cause hum as it flows in an unbalanced audio interconnect cable. However, harmonics of 60Hz that are generated from lighting dimmers or switch-mode power supplies sound like Buzzz mixed with a bit of Hummm and are more easily coupled by even smaller currents. Harmonics can add together when equipment is powered from different phases, so clearly there is an advantage to specifying same-phase electrical service to power the electronics systems in most cases....
Any leakage currents on the safety ground wires of split single phase load circuits fed by different phase legs will add together due to the 240V potential difference....
Power conditioners do not solve any of these common problems: Cross phase coupling (doubles hums & buzzes) .... What actually does solve them: Same phase power. http://www.exactpower.com/elite/assets/pdfs/theTRUTH.pdf "Any leakage currents on the safety ground wires of split single phase load circuits fed by different phase legs will add together due to the 240V potential difference.... "
240V potential difference? Voltage measured from one receptacle Hot contact to the other receptacle Hot contact, of each split wired duplex receptacle, fed by a 3 wire 120/240V MWBC.
Jmho this is at play as well.
(Jmho, it also depends on the design of the audio equipment power supply and how the designer connected the B- and signal ground to the metal chassis of the equipment.
The quality of the power transformer used in the equipment can make a big difference. How well does it control capacitance coupling from the primary winding to the secondary winding(s).
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