Dedicated Home Theater Circuits, Does Phase matter?

M

MGB

Audiophyte
When running multiple new dedicated home run circuits for a home theater, does the phase matter? Should all the breakers be on the same 120V pole? Would having one amplifier 180° out of phase make a difference?
 
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S

Speedskater

Audioholic Chief
Three different situations:
1] most home theater set-up only need one 20 Amp circuit.
2] for larger systems, run one 120V feeder from the main panel to a 6 breaker box in or near the A/V room.
for huge systems with lots of big amps, run a 240V(120/120V) Multi-Wire branch circuit to the room then the breaker box.
* * * * * * *
if you have to run two circuits, then having them on the same pole (leg) is slightly better.
P.S. it's 180° and it's a single phase system, so it would be opposite polarity difference.
 
WaynePflughaupt

WaynePflughaupt

Audioholic Samurai
I’d suggest keeping all gear in the system on the same phase.

At our previous house I put in two dedicated circuits for the HT gear. However, the TV was on an outside wall with the existing electrical outlet under a window, so I couldn’t get a line from the dedicated circuit there.

Consequently, I ended up with some 60 cycle noise. A check determined the circuit the TV was on, was on the opposite leg from the HT circuits. When I moved that circuit to the same leg, that took care of the noise.

Regards,
Wayne A. Pflughaupt
 
M

MGB

Audiophyte
Thanks for all the input. Seems unanimous that all the equipment be on the same leg/phase.

How many circuits and at what amperage would you run for:
2xMC1.25KW monoblock - 12A draw each
2xMC257 7 channel amp - 12 A draw each
2xB&W DB1D Subwoofers - 3A draw each
MX170 A/V processor - 1A
Panasonic 4K player. - 0.5A
LG C8 77” OLED
 
S

Speedskater

Audioholic Chief
Wow, that's a big system!
two 7 channel amps?
a 2000 Watt sub-woofer and a 3 Amp current draw doesn't compute.
* * * * * * *
anyway, I'd call that a huge system.
Use a multi-wire 240V : 120/120V feeder to the room and a 6 breaker box.
 
M

MGB

Audiophyte
Wow, that's a big system!
two 7 channel amps?
a 2000 Watt sub-woofer and a 3 Amp current draw doesn't compute.
* * * * * * *
anyway, I'd call that a huge system.
Use a multi-wire 240V : 120/120V feeder to the room and a 6 breaker box.
Yep, I’m working towards a 13 channel Dolby Atmos (7.2.6).
I contacted B&W directly regarding the subs they said the Class D amps are very efficient. I was surprised too.

I could run a sub panel to HT room, but if it’s 120/120V does that bring up the phase issue again? Half the equipment on one leg and half on the other? Wayne A. Pflughaupt’s reply indicated that it can cause an issue with audio, having the system power out of sync. Or am I’m obsessing over a non issue?

Thanks again for a the help.
 
Verdinut

Verdinut

Audioholic Ninja
IMO, two 20 amp circuits should be amply adequate to feed enough power to operate your equipment. Music doesn't require lots of power continuously and power supply capacitors provide most of the required amp power for peak demands which normally last for fractions of seconds only. Keep in mind that circuit breakers will also handle more current than their rating for a few seconds before tripping.
 
S

Speedskater

Audioholic Chief
I could run a sub panel to HT room, but if it’s 120/120V does that bring up the phase issue again? Half the equipment on one leg and half on the other? Wayne A. Pflughaupt’s reply indicated that it can cause an issue with audio, having the system power out of sync. Or am I’m obsessing over a non issue?
With RCA unbalanced interconnects, the is slightly more noise when on both poles.
With balanced XLR interconnects, there is no difference.
With real big power amplifiers, there is a small advantage to having each pair on both legs when using a Multi-Wire Branch Circuit. Less AC voltage drop.
 
WaynePflughaupt

WaynePflughaupt

Audioholic Samurai
If your speakers are fairly efficient and won’t demand much from the amplifier, I’d second the motion that two 20-amp circuits will be sufficient.

However, if your speakers will be demanding a lot from the amps, I’d consider a third circuit, as heavy demands from the amplifier circuits could drag down voltage on the line. Might not be bad to get the other gear off that to another circuit with a more stable feed.

With two circuits on the same phase, I wouldn’t use 240v multi wire, as this wire typically has the two 120v legs sharing a common neutral wire. That’s an efficient arrangement for a 240v line, because the primary legs are out of phase so they alternate use of the common wire.

However, with two circuits on the same phase, both circuits are using the common simultaneously, which means it is double-loaded. Probably not a good thing.

Regards,
Wayne A. Pflughaupt
 
S

Speedskater

Audioholic Chief
With two circuits on the same phase, I wouldn’t use 240v multi wire, as this wire typically has the two 120v legs sharing a common neutral wire.
That's what is good about it for a huge system that has many large amplifiers.
The amps have to be paired. i.e. Left front on one leg and Right front on the other. It reduces the voltage drop on the Neutral.
P.S. Without the 120V/120V part, it's not a multi-wire system, it's just a 240V system.
 
Verdinut

Verdinut

Audioholic Ninja
eavy demands from the amplifier circuits could drag down voltage on the line. Might not be bad to get the other gear off that to another circuit with a more stable feed.

With two circuits on the same phase, I wouldn’t use 240v multi wire, as this wire typically has the two 120v legs sharing a common neutral wire. That’s an efficient arrangement for a 240v line, because the primary legs are out of phase so they alternate use of the common wire.

However, with two circuits on the same phase, both circuits are using the common simultaneously, which means it is double-loaded. Probably not a good thing.

Regards,
Wayne A. Pflughaupt
In a 240 volt circuit, the current is between the two out of phase 120v live wires, so no wire is overloaded. I may be wrong but IMO, there is no current going through the neutral wire on a 240 volt circuit.
 
S

Speedskater

Audioholic Chief
In a 240 volt circuit, the current is between the two out of phase 120v live wires, so no wire is overloaded. I may be wrong but IMO, there is no current going through the neutral wire on a 240 volt circuit.
Yes, many 240V circuits don't have a Neutral wire. But if the appliance or HVAC also has a 120V control system, then it would have a Neutral wire. Like a kitchen range (stove).
 
WaynePflughaupt

WaynePflughaupt

Audioholic Samurai
In a 240 volt circuit, the current is between the two out of phase 120v live wires, so no wire is overloaded.
Correct, that is the point I was trying to make (apparently I failed).

I was talking about using a multi-wire cable, which is normally for 240v (two 120v lines from both legs) , to carry two 120v circuits from the same leg. I don’t think that’s a good idea.

Regards,
Wayne A. Pflughaupt
 
Verdinut

Verdinut

Audioholic Ninja
Correct, that is the point I was trying to make (apparently I failed).

I was talking about using a multi-wire cable, which is normally for 240v (two 120v lines from both legs) , to carry two 120v circuits from the same leg. I don’t think that’s a good idea.

Regards,
Wayne A. Pflughaupt
Well, a variation of voltage would depend on the total average power which is consumed through the main entrance breakers. If the two 20 amp circuits are connected on the same phase leg, and the main entrance of a building has a 1,000 amp rating, the situation might be different. It's a question of percentage of power consumed by the HT system vs the average total power continually consumed within the building. :)

Cheers,
André
 
S

Speedskater

Audioholic Chief
I was talking about using a multi-wire cable, which is normally for 240v (two 120v lines from both legs) , to carry two 120v circuits from the same leg. I don’t think that’s a good idea.
For extremely large systems, I have the opposite viewpoint.
* * * * * * * * * *
But 'MGB' may be the only person to ever read this thread with such a large system.
 
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