Wiring Question (1 Viewer)

[Daniel_M]

I've got three A/C lines, five video cables (3 component
one SVideo, &one composite) plus all five speaker
cables running parallel along the heating duct enclosure
that runs the legnth of my H.T.
The A/C lines are separated
from the others as much as I could (the width of the
duct enclosure about 15 inches and all lines run
together for about 4 feet before the speaker wires
and video cables branch off. There is also a cablevision
wire running the length of the duct.
I can cut out the cablevision wire but everything else
has to stay. Anyone foresee audio or video interference
problems with this setup? Nothing is hooked up yet
so it's not something I can test myself for awhile yet.
Thanks,
Dan

 

[Wayne A. Pflughaupt]

Daniel,
There won’t be any problems. The way you have described it, everything has been done right. The 4-ft. parallel run is not long enough to be a concern; that’s why the important cables are shielded.
Are the AC lines dedicated circuits for your system? If so, make sure they are wired to the same electrical leg at the service panel.
Cheers,
Wayne A. Pflughaupt

 

[Daniel_M]

Yes, the A/C lines run directly
from the service panel. One is a
240 volt line (red, black, white & ground)
which will be hooked into a 30 amp breaker
to run a heavy duty amp I will be purchasing
in the near future.
Could Wayne or anyone else clarify
what is meant by "wired to the
same electrical leg at the service panel"?
Thanks Dan

 

[Wayne A. Pflughaupt]

Daniel,
A typical house has the following electrical service from the power company: Two hot legs (aka “phase”), 120VAC each, and one return or neutral. If you remove the cover from your service panel, you will see one hot leg connected to one group of breakers, and the other leg connected to another other group of breakers. The circuits in the house are supposed to be split even between the two legs. You will find the neutral leg connected to a buss bar, and all the white wires from the circuit feeds (i.e., romex) are connected to the buss bar, as are all the circuit grounds. 240VAC service is derived by utilizing both hot legs. 240V circuits require a double-gang breaker that will switch both legs simultaneously.
To answer your question, all 120VAC circuits for a home theater should be connected (via circuit breakers) to the same hot leg at the service panel, to avoid the possibility of ground loops.
Incidentally, what kind of amp are you using? The only amps I’ve ever seen that require 240V service are for commercial applications.
By the way, Daniel, welcome to the Forum!
Regards,
Wayne A. Pflughaupt

 

[Daniel_M]

Hi Wayne,
Thanks for the welcome (actually I've been
lurking for a couple of years) and thank you
for your explanation of the different legs
of the service box. I probably won't hook up
breakers myself but I will make sure it's
done right thanks to you.
The amp is my dream amp that I've been
saving up for for awile now and I will probably
buy in the fall. It's the Cinepro 3K3 III
and it's a mother @ over 3000 Watts. It doesn't
have to run off 240v as a matter of fact
you have to special order the unit with the
240v conversion. I've done alot of research on
the the Cinepro and most people (including Cinepro)
say you get a marked improvement in performance
at the higher amperage/voltage.
Since I was bringing in new A/C anyway I thought I
might as well run a 240volt line although it was
MUCH harder to work with (it was a 75 foot run from
the fuse box) and alot of cursing and swearing went
down as I fished it through the PVC and into the
home theater. I hope it'll be worth it!
Thanks again,
Dan

 

[Daniel_M]

Sorry make that Cinepro model number
3K6 III. It's six channels, not 3.
Cheers,
Dan

 

[Rob Roth]

Anybody (Wayne P.?) have an opinion on wiring for dedicated circuits? The standard method is romex wherein the wires run parallel. The alternative is using 'raceway' and running separate wires which can be twisted together. Twisting the hot and neutral together supposedly reduces common mode interference (the ground stays separate). I know lots of electronics use twisted pair technology to reduce noise- unsure how much it helps in our applications.

 

[Wayne A. Pflughaupt]

Rob,
quote: The alternative is using 'raceway' and running separate wires which can be twisted together. Twisting the hot and neutral together supposedly reduces common mode interference (the ground stays separate).[/quote]
This practice is relevant to balanced audio signal applications, not electrical power. (Actually, there is more to the superior common mode rejection properties of balanced signals than merely twisting the signal wires, but there’s no reason to get in to that here.)
There is no reason to give dedicated home theater circuits any treatment of this sort, as common mode interference is not an issue with electrical power. The primary issue with electrical service, if any, is “dirty” or less than pure AC voltage, a problem that will not be addressed with special wiring techniques.
The main electrical concerns for home theater are:[*]A certain amount of isolation from other appliances in the home (total isolation cannot be achieved without a dedicated power transformer).[*]An adequate current supply that is not compromised or diminished by sharing a circuit with lighting or other appliances.
These goals can be easily realized with one or more dedicated circuits, and to a greater extent with isolated ground circuits.
Regards,
Wayne A. Pflughaupt
[Edited last by Wayne A. Pflughaupt on July 27, 2001 at 01:27 PM]