Home Theater Electrical Help

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  #1  
Old 10-31-05, 11:09 AM
thylantyr
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Home Theater Electrical Help

This is a DIY project. I need to install 8 outlets on a wall
in the home theater for amplifiers and misc. electronics.

I will have eight 4000w pro audio amplifiers each
recommending a 20A circuit, but the amplifier specification
claim up to 30A draw at full load, 15A typical.

The wiring run length for each outlet is ~ 50 feet away
from the electrical service panel {breaker box}.

I don't feel comfortable running 8 seperate Romex 10/2
lines, each with a 30A breaker. For some reason, I feel
that it's not enough current capability to minimize
voltage drops at full load.

Questions:
1. Is there such a thing as stranded 8/2 Romex?

2. If no to question 1. Can I just run THHN #8 stranded wire bundled and only use 1 bigger ground wire for safety?
 
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  #2  
Old 10-31-05, 11:28 AM
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You may not run 30-amp circuits. You must run 20-amp circuits as specified by the manufacturer.

50 feet is not far enough to worry about. You don't need #8. You don't even need #10. Regular #12 will be plenty.

8 times 15 amps is a significant load (60% of the total capacity of a 100-amp service, or 30% of the total capacity of a 200-amp service). Make sure your house service will not be overloaded.
 
  #3  
Old 10-31-05, 11:55 AM
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Consider connecting a "sub-panel", supplied by a 3-wire "Feeder" ( + Grounding-wire ) which is located as near as possible to the "center" of where the loads are physicaly located to mimimized the lenth of the individual Branch-Circuits that extend from the S-P to the individual connection- points.

As to the rating of the Branch-Crcuits, how is the load-connection to the Branch-Circuit conductors effected? A cord-plug inserted into a receptacle? For such connections, the receptacle should conform to the cord-plug that the load was equipped with.
 
  #4  
Old 10-31-05, 01:00 PM
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You are really installing 32kW of audio amplifiers in your home? I'm glad you aren't my neighbor! Do your amps have a cooling system? That kind of gear will heat up the room in a hurry.

As John said, you need to install the type of circuit specified by the manufacturer of the amplifiers. You are not allowed to have a 30A general purpose receptacle in your home. If you do install 20A receptacles, then 12/2 romex is totally acceptacle over 50 feet. If you want to waste the money on it, you can run 10/2 romex to the 20A receptacles to minimize voltage drop, but you still must use a 20A breaker.
 
  #5  
Old 10-31-05, 01:10 PM
thylantyr
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Originally Posted by John Nelson
You may not run 30-amp circuits. You must run 20-amp circuits as specified by the manufacturer.

50 feet is not far enough to worry about. You don't need #8. You don't even need #10. Regular #12 will be plenty.

8 times 15 amps is a significant load (60% of the total capacity of a 100-amp service, or 30% of the total capacity of a 200-amp service). Make sure your house service will not be overloaded.
My mistake. The manufacturer doesn't specify what
service to use, they just tell you what the amplifier draws
under three difference conditions.

The amplifier has two seperate circuit breakers on
the chassis of 15A each, one for each channel of a 2ch
amp.

Power consumption;
8 ohms typical= 6.4, full= 12.5, maximum= 25.5
4 ohms typical= 10.0, full= 20.1, maximum= 42.2
2 ohms typical= 14.5, full= 30.6, maximum= 65.7

Current Consumption Notes:Typical- 1/8 power, pink noise, represents typical program with occasional clipping. Full- 1/3 power, pink noise, represents severe program
with heavy clipping. Maximum- continuous sine wave at 1% clipping.

http://www.qscaudio.com/pdfs/rmx3ru.pdf

****

I'm estimated the worse case to be the 2 ohm operation
which is rated to draw 30.6A. I pretty sure I won't push
the amplifier hard, but I wanted to over-engineer the needs.

Here is my fuzzy math

#10 [black] hot wire run 50' = 0.049 Ohms.
#10 [white] neutral wire run 50' = 0.049 Ohms.

Total resistance in the loop is 0.099 Ohms.

Pass 30A though this and you get 2.99V as the drop
and 88 watts of losses, 2.5%? Is this acceptable?

The part I don't understand is how this calculator located
here; gives me 3.6V drop with 3% loss ???
http://www.powerstream.com/Wire_Size.htm

If the amp draws 30A, would the 30A breaker trip exactly
at 30A or is there some headroom before it trips?

 

Last edited by thylantyr; 10-31-05 at 02:33 PM.
  #6  
Old 10-31-05, 01:13 PM
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What type of plug is on the end of the amp's cord?
 
  #7  
Old 10-31-05, 01:16 PM
thylantyr
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Originally Posted by PATTBAA
Consider connecting a "sub-panel", supplied by a 3-wire "Feeder" ( + Grounding-wire ) which is located as near as possible to the "center" of where the loads are physicaly located to mimimized the lenth of the individual Branch-Circuits that extend from the S-P to the individual connection- points.

As to the rating of the Branch-Crcuits, how is the load-connection to the Branch-Circuit conductors effected? A cord-plug inserted into a receptacle? For such connections, the receptacle should conform to the cord-plug that the load was equipped with.
I checked out my main panel. Square D breaker box
with a center main circuit breaker of dual 125A with 16
positions for additional breakers, plug in type circuit breakers. I have 6 unused slots available and the existing
load isn't high. Oven, dryer, couple rooms, etc. Seems over-engineered.

This electrical panel was upgraded a few years ago when
the previous home owner did remodeling. I'm assuming
the service is higher than 125A x 2 = 250A ? in order
to support dual 125A breakers?

I'm positive that the upgrades were signed off by city
inspectors, but I don't know if my service is really 200A or
greater?

Consider connecting a "sub-panel",

When I looked at this panel, I don't really know how
I can tap off of it with three heavier gauge wires to
feed a subpanel in the house, otherwise that would be cool,
hence just wiring eight 10/2 lines to the box idea.
 

Last edited by thylantyr; 10-31-05 at 01:28 PM.
  #8  
Old 10-31-05, 01:20 PM
thylantyr
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Originally Posted by John Nelson
What type of plug is on the end of the amp's cord?
That is where the comedy begins. To make the amplifier
user friendly with home owners and what not, they [manufacturer] installs an ordinary 15A cord like so.
http://www.weisd.com/store2/CABPWR-1000-06.jpg

Most people that run these amplifiers don't get optimum
performance when they run 15A power cords at great
distances as they create too much voltage drops. I was
going to use a 3 foot [or less] cord to keep losses low.
 
  #9  
Old 10-31-05, 01:27 PM
thylantyr
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You are really installing 32kW of audio amplifiers in your home?

That is the plan.

Do your amps have a cooling system? That kind of gear will heat up the room in a hurry.

Pro amps have fans.

You are not allowed to have a 30A general purpose receptacle in your home.

I think what I will do violates code, but I need my music

I don't get it though. I already have 40A breaker {dual} for
the oven, another 30A {dual} for the dryer, and another
30A {dual} for a garage oven that we removed which frees
up space for me

Why not just use this and install more 30A? I noticed the
wire awg for the 30A circuits are #10 and this was signed
off by the city? The 40A is #8 .

So, if I add more 10/2 on 30A and don't exceed service,
why is that bad?

 
  #10  
Old 10-31-05, 01:28 PM
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Originally Posted by thylantyr
This electrical panel was upgraded a few years ago when
the previous home owner did remodeling. I'm assuming
the service is higher than 125A x 2 = 250A ? in order
to support dual 125A breakers?
Your service is a 125A, 240V service. That means you can get a total of 30,000W. These days 100A is the minimum size service allowed for a residence, so yours is normal but not have a lot of room for expansion.

When I looked at this panel, I don't really know how
I can tap off of it with three heavier gauge wires to
feed a subpanel in the house, otherwise that would be cool,
hence just wiring eight 10/2 lines to the box idea.
If you were to install a subpanel, you would likely install a 60A double pole breaker and run #6 wires from the breaker to the subpanel. If you do take this course of action, you should get a good home wiring book and read it. There are a lot of details to get right, and a book will do a better job than the postings here.
 
  #11  
Old 10-31-05, 01:40 PM
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I think what I will do violates code, but I need my music
This is the wrong way to think; the code is written for safety. There have been at least two code legal solutions to your problem posted already.

Originally Posted by thylantyr
I don't get it though. I already have 40A breaker {dual} for
the oven, another 30A {dual} for the dryer, and another
30A {dual} for a garage oven that we removed which frees
up space for me

Why not just use this and install more 30A? I noticed the
wire awg for the 30A circuits are #10 and this was signed
off by the city? The 40A is #8 .

So, if I add more 10/2 on 30A and don't exceed service,
why is that bad?
The oven and dryer are not "general purpose" receptacles. The use special large plugs that only ovens and dryers can plug in to. This is allowed because these large appliances are designed to handle that much power.

Appliances with standard cords on them are only designed to be plugged in to a 15 or 20A circuit. That means if the appliance has an electrical failure, it can withstand up to 20A without bursting into flames. If you had a 30A breaker on that circuit, you have a serious house fire risk.

It is very unsafe and illegal to put a standard 15 or 20A receptacle on a 30A breaker.

EDIT: I just looked at the PDF file you posted, and a 20A circuit is correct for this device. Run 12/2 or 10/2 Romex from a 20A breaker to a 20A simplex receptacle for each amplifier.
 
  #12  
Old 10-31-05, 01:42 PM
thylantyr
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Your service is a 125A, 240V service. That means you can get a total of 30,000W.

.. so I need to turn on the stereo when the dryer, oven
and others stuff is off

If I were to ask the electrical company to upgrade
to 200A, what do they do? Beef up the wires from
the pole to box and install 200A breakers instead of 125A
or do they install a whole new box/meter to support
this ?

If you were to install a subpanel, you would likely install a 60A double pole breaker and run #6 wires from the breaker to the subpanel. If you do take this course of action, you should get a good home wiring book and read it. There are a lot of details to get right, and a book will do a better job than the postings here.

Subpanel inside the room? If so, is that normal for
people to do this? Install a dual 60A breaker on the main
panel, run four #6 wires {or beefier} from main to subpanel?
 
  #13  
Old 10-31-05, 01:49 PM
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The power company won't upgrade your service. You have to have an electrician do that. It usually costs between $1000 and $2000.

If the amps have standard 15-amp plugs, then they should work just fine on a 20-amp circuit. Note that a 30-amp circuit will have exactly the same voltage drop as a 20-amp circuit, given that you are using the same size wire. So voltage drop is no reason to make your installation hazardous.
 
  #14  
Old 10-31-05, 01:52 PM
thylantyr
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It is very unsafe and illegal to put a standard 15 or 20A receptacle on a 30A breaker.

Hypothetical;
If eight 30A receptacles were installed on the same wall
in a room, would that be considered an unusually
installation to have so many circuits so close?

Under these conditions, would Romex 10/2 for each
receptacle be normal for a 50 foot run?
 
  #15  
Old 10-31-05, 01:55 PM
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Originally Posted by thylantyr
If I were to ask the electrical company to upgrade
to 200A, what do they do? Beef up the wires from
the pole to box and install 200A breakers instead of 125A
or do they install a whole new box/meter to support
this ?
A service upgrade is the responsibility of the homeowner. A 200A service requires a new meter box, conduit riser, and panel box. This almost always should be done by a professional electrician and will cost between one and two thousand dollars.

This is probably an overkill, but you can do a demand load calculation to determine how much capacity you have in your service. Google the term and you will find a procedure.

Subpanel inside the room? If so, is that normal for
people to do this? Install a dual 60A breaker on the main
panel, run four #6 wires {or beefier} from main to subpanel?
Subpanel installation is a very common home wiring task. You should be able to find numerous good descriptions of the process in the archives of this board and numerous how-to books at home centers.
 
  #16  
Old 10-31-05, 02:03 PM
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Originally Posted by thylantyr
If eight 30A receptacles were installed on the same wall
in a room, would that be considered an unusually
installation to have so many circuits so close?
It would be extremely rare. Devices that actually require 120V 30A circuits are very rare. Eight circuits of any size on one wall would be very rare outside of commercial or industrial buildings.
 
  #17  
Old 10-31-05, 02:04 PM
thylantyr
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Originally Posted by John Nelson
The power company won't upgrade your service. You have to have an electrician do that. It usually costs between $1000 and $2000.
When the electrican upgrades your main panel, how
does he know if the wires from the pole to house
is adequate for the upgrade, in this example going
from 125A to 200A ? Does he just look at wire gauge
from pole to house and say "yeah, that will work it's big
enough? "

If it is not, does he contact the electrical company to
beef up these wires first before he proceeds with the
upgrade or do I have to call the electrical company?

I'm not familiar with procedure

Do you think the electric company over-engineers the
pole-to-house wiring, ie if your box is 100A service,
will the mains coming in from the pole be rated much
higher?
 
  #18  
Old 10-31-05, 02:06 PM
thylantyr
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Originally Posted by ibpooks
It would be extremely rare. Devices that actually require 120V 30A circuits are very rare. Eight circuits of any size on one wall would be very rare outside of commercial or industrial buildings.
Would having such a system meet code for residential ?
 
  #19  
Old 10-31-05, 02:15 PM
thylantyr
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EDIT: I just looked at the PDF file you posted, and a 20A circuit is correct for this device. Run 12/2 or 10/2 Romex from a 20A breaker to a 20A simplex receptacle for each amplifier.

Are all 'new' circuit breakers of the "Hydraulic/Magnetic Circuit Breaker" variety? not thermal based?

Does that mean the 20A breaker trips at 20A or does it
allow peak currents to pass without tripping?

My assumption is that you can peak more than 20A,
but if you sustain 20A it trips
 
  #20  
Old 10-31-05, 02:19 PM
thylantyr
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/General curiosity question;

General Purpose
20A breakers and under is 'general purpose',
30A/40A for large appliances. I've seen 25A breakers,
what application are those for? I can't recall seeing
equipment that uses 25A receptacles/plugs, which plugs
might those be
 
  #21  
Old 10-31-05, 02:58 PM
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The electrician will contact the power company to find out if the service wires need to be upgraded. It's a power company decision. They often approve the upgrade with no change to their wires, not always because the wires are adequate, but because the power company doesn't like to spend money.

The code doesn't care if you want to put 20 circuits on the same wall. And doing so would not suggest the need for larger wire.

The term "general purpose" is not precisely defined. Most but not all 15-amp and 20-amp circuits are general purpose. It is commonly used as the opposite of "dedicated".

Circuit breakers include both magnetic and thermal tripping mechanisms, and sometime even other mechanisms. Circuit breakers allow small overcurrents for quite a while (hours), large overcurrents for some period of time (minutes), and short circuits for almost no time at all (milliseconds).

Describing all the different kinds of circuits and what they are used for would make this already long thread ten times longer, and still wouldn't help with this situation.
 
  #22  
Old 10-31-05, 03:15 PM
thylantyr
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Thanks for the help.

Right now I guess I need to make a decision on
which methodolgy to use because drywall will be going
up soon.

Two ideas;

1. Run eight Romex cables from room wall to main
panel for now, don't connect them up until service is
verified.

2. Instead of running eight Romex cables, run a thicker
line from the room wall to main panel, don't connect them
up until service is verified. Install the subpanel inside
the room with eight dedicated breakers just for the home
theater and install those eight outlets on the wall.

Which idea is more 'normal' ? I don't know, I've never seen
a subpanel in a home before, is this more practical than
running eight Romex lines down a wall ?

If I chose the subpanel method with a thicker cable,
is there requirements on which cable to use? Do they make
#4 or #6 Romex? or do I just get THHN single wires and
run them as is through walls, attic , etc.

 
  #23  
Old 10-31-05, 04:19 PM
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What is the impedance of the speakers you are driving? 2 ohm speakers are pretty uncommon. What is the efficiency of the speakers? Or are you just putting in huge amplifiers without consideration of the overall system design? If your speakers are 8 ohm there's no point engineering the solution for 2 ohm speakers...

Is this for a 7.1 surround or for a multi-amped system (multiple amplifiers per channel)? In a 7.1 surround the effects channels usually carry a lot less signal than the mains or sub...

FWIW my main system has 1300W (six 150W amps and four 100W amps) in a two-channel setup (5 amps each left and right). I can't listen to anything on this system anywhere near full volume without causing permanent hearing loss...
 
  #24  
Old 10-31-05, 04:26 PM
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Here are a few items which have been confusing in all the posts:
1) You mention some breakers for each channel. These are probably at low voltage so the current rating is not directly related to the discussion of the input power to these amps.

2) All the discussions have assumed you are feeding 120 VAC as the input to these units. The largest general purpose receptacle for 120 is 20 amps. Are the amps actually 120 or are they set up for 240 input?
2a) There are specialized receptacles rated for 30 amps. I do not know if code allows them to be used in your situation.


3) Circuits are designed to operate on a continuous load not exceeding about 80% of the rating. All breakers will take full load current on occasion, and larger peak currents momentarily. Any equipment should specify on the rating plate the circuit capacity required to run it.

4) When you mentioned running indidual stranded conductors, this can be done but of course the conductors MUST be run in conduit.

5) You mentioned 32 KW of power. In my area this would cost $4.80 per hour to run, and the heat generated would heat a 3 BR house!

6) Please do not take likely the comments from the excellent professionals on this forum regarding safety and codes. These are serious issues.
 
  #25  
Old 10-31-05, 04:35 PM
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I looked at the specs for the amp. I read: "Full- 1/3 power, pink noise, represents severe program with heavy clipping. Maximum- continuous sine wave at 1% clipping."

Unless you are just going for decibels and don't care about sound quality, you won't be driving anywhere close to "full power". A system driven into clipping will sound like crap, plain and simple.

Again, unless you are just trying to knock your walls down....

Oh yeah, a clipped input signal will destroy most loudspeakers...
 
  #26  
Old 10-31-05, 05:05 PM
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If those are standard IEC connectors, I doubt they will do more than 20A anyway. An you'll likely have to search high and low for 20A-120V IEC cords (in my collection of them, only one is a #16, the rest are #18),

You have to do the math to figure what is cheaper for you, running the circuits from the main panel, or a sub panel. At that distance, you are probably better off running to the main.

25A is for applcations that list them, like A/Cs and fixed heaters and such.
 
  #27  
Old 10-31-05, 10:51 PM
thylantyr
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re: speakers

It's a DIY system, four tower line array.

CAD sketch;
http://home.pacbell.net/lordpk/proto/Prototype-13_1.jpg

Eight 15" woofers
Sixteen 8" midranges
Sixteen 8" pro audio tweeters

Six pro amplifiers to drive this array, ideally eight would
be best plus two more pro amplifiers to drive two low
frequency subwoofers [not shown in sketch]. I can easily
use ten 4000w amps for this crazy rig.

There is eight to ten amplifiers already and I haven't even included the center and surround speakers/amps and other misc electronics.

I talked to the QSC engineer on their forum, he recommends a dedicated 20A circuit for each amplifier
for music, but if you were to bench test the amplifier
using sine waves, it has the potential to draw 65A. That's
nasty ...

If this was a normal system, the solution is easy, but
this is very abnormal audio system, hence why I'm thinking too much about over-engineered electrical system.
 
  #28  
Old 10-31-05, 11:08 PM
thylantyr
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1) You mention some breakers for each channel. These are probably at low voltage so the current rating is not directly related to the discussion of the input power to these amps.

Most home amplifiers have a fuse to protect itself, but
these pro amplifiers are beefy and have two 15A breakers built in them, according to the owners manual and drawing, they use one 15A breaker for one channel of the
amplifier, and another 15A breaker for the other channel.

That is the comedy. A 20A circuit for each on is recommended, but the amplifiers themselves are fused
at 30A. // hehe //

All the discussions have assumed you are feeding 120 VAC as the input to these units. The largest general purpose receptacle for 120 is 20 amps. Are the amps actually 120 or are they set up for 240 input?

I believe you can order or configure them for both. The discussion is based on 120v input though.

There are specialized receptacles rated for 30 amps. I do not know if code allows them to be used in your situation.

doh..


Circuits are designed to operate on a continuous load not exceeding about 80% of the rating. All breakers will take full load current on occasion, and larger peak currents momentarily. Any equipment should specify on the rating plate the circuit capacity required to run it.

Even if a 30A circuit was installed per amplifier, using
that 80% rule, that only gives me 24A continuous.

When you mentioned running indidual stranded conductors, this can be done but of course the conductors MUST be run in conduit.

Thanks for that tip.


You mentioned 32 KW of power. In my area this would cost $4.80 per hour to run, and the heat generated would heat a 3 BR house!

The only good news is that music is dynamic, low
duty cycle, unlike a dryer or oven. That's why the manufacturer claims that the 20A circuit is fine for music,
but not to play test tones through they amplifier otherwise
the amplifier can really suck current bad, up to 65A.
Maybe I can 'burp' some tones momentarily to make
the intestines vibrate when my friends come over to listen?
/// evil ///

Please do not take likely the comments from the excellent professionals on this forum regarding safety and codes. These are serious issues.

I think my line array will be more deadly than the
amateur house wiring
 
  #29  
Old 10-31-05, 11:51 PM
thylantyr
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More comedy.

For reference. The RMX4050 amplifiers I want to use is
'entry level' pro audio amplifiers, but very good for the
money.

I would love to get some of their older amplifiers to
drive the subwoofers, the QSC Power Light series 6.0
or 9.0, 7kw and 9kw respectively.

For the 120V version of these amplifier, they hardwire the
AC cord inside the amplifer and you need NEMA L5-30
receptacle. Page 9.
http://www.qscaudio.com/pdfs/pl60iimnl.pdf

QSC isn't the only manufacturer of pro audio amplifiers,
Crown audio has a 5kw monster amplifier that also has
the AC cord hard wired inside and they use a three
prong 30A plug, sorta looks like a dryer plug. Page 11.
http://www.crownaudio.com/pdf/amps/128313.pdf

Three different monster amplifers, one works with
20A service, the other two run off 30A service and each
uses a different plug.

So.................. I need to install 30A service and change
out receptables *if* I want to use those other amplifiers.



Maybe I should order these power amplifiers in 240V
AC input versions? But I have to figure out if they share
a common plug ? /hehe

/crazy
 
  #30  
Old 11-01-05, 08:16 AM
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I hesitate to offer any more advice than hiring a professional electrician to at least help you with the design and perhaps installation of your wiring. You're talking about maybe a service upgrade, maybe a subpanel installation, a lot of wiring, etc. My impression is that your electrical experience does not match a project of this scope.

I suggest this because you're planning on installing what would otherwise be a very large commercial-grade system in your home and as such you should have some professional oversight in the installation. This site is a great resource for typical home wiring projects, but what you are proposing is beyond the pale. Before you do something that could seriously damage or destroy your audio equipment, or more seriously, burn down your home with you in it, please have a professional look over your plans.

I would offer this advice to anyone looking to install commercial-grade equipment of any type in their home.

As a side note, I used to work technical detail for an auditorium, and we had 16kW of QSC amplifiers on 4 channels (4kW/channel). The sound was deafening in a 1,000 seat auditorium with the power half way up. I really think your system is far too large for the space you have, even running the amplifiers very low.
 
  #31  
Old 11-01-05, 08:53 AM
thylantyr
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Originally Posted by ibpooks
I hesitate to offer any more advice than hiring a professional electrician to at least help you with the design and perhaps installation of your wiring. You're talking about maybe a service upgrade, maybe a subpanel installation, a lot of wiring, etc. My impression is that your electrical experience does not match a project of this scope.

I suggest this because you're planning on installing what would otherwise be a very large commercial-grade system in your home and as such you should have some professional oversight in the installation. This site is a great resource for typical home wiring projects, but what you are proposing is beyond the pale. Before you do something that could seriously damage or destroy your audio equipment, or more seriously, burn down your home with you in it, please have a professional look over your plans.

I would offer this advice to anyone looking to install commercial-grade equipment of any type in their home.

As a side note, I used to work technical detail for an auditorium, and we had 16kW of QSC amplifiers on 4 channels (4kW/channel). The sound was deafening in a 1,000 seat auditorium with the power half way up. I really think your system is far too large for the space you have, even running the amplifiers very low.
My specialty is electronics as I've been doing it for
decades, it shares the same theory as electrical work
but being an electrician requires skill in meeting
electrical codes and knowing what products exist in the
market to accomplish such a task. That is what I don't
know, hence I'm here

After thinking about all these amplifiers and how they
come in different wiring flavors, the subpanel idea
seems to be the best. Bringing 240V/ ~ 100A service
into the room would make the scenario very flexible
and I can wire the outlets right below the subpanel
on the wall. Realistically, using dual 60A breakers
to feed the subpanel would be fine, but I want to over-engineer the wiring needs just in case I do upgrades later.
I don't want to tear down walls because I used skinny wire.

One idea;
I would like to run three #2 cables for this, two hot,
one neutral, if the cable is flexible enough for me to
squeeze through the framing. Someone mentioned it
has to be in conduit, is that one cable per conduit or can
I bundle all three cables inside one larger conduit? Or
can I pick one of those two options? Would this be THHN
cable? Does it come in different color sleeving or is it
all in black?

I really think your system is far too large for the space you have, even running the amplifiers very low.

Audio for me is 1/2 art, 1/2 audio, no different than
someone making a 1000 horse muscle car. It's a DIY
hobby to build crazy stuff.

Here is a sneak peak at an array I made for a friend. It's
what I call an entry level array.
http://home.pacbell.net/lordpk/robarray/

The sound is quite amazing and it gets driven by two
amplifiers, one being a 2400w QSC amp. I've blown
the 20A circuit breaker when I push this system hard.

The tweeters are wired for 0.8 ohms, the midwoofers
are wired for 2 ohms for maximim SPL.

This is a baby system compared to the one I have planned
so I'm taking the electrical serious, DIY style though. I do
like to tackle home projects myself until I hit a brick wall
and then I farm out the work. With help given so far,
I think I can get there eventually. I'd like to start wiring
in 2 weeks so I'm still researching.
 
  #32  
Old 11-01-05, 09:22 AM
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Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
In order to add a sub panel and/or to increase your incoming service will require a permit and an inspection. You will not pass inspection if you try to do this yourself until and unless you learn more. You will have to do some reading on your own, and have an electrician review your plans.

A sub panel requires four wires, not three. You need two hots, a neutral and a ground. Yes, the wires come in different colors. In fact, they need to be different colors. Individual wires run in conduit. They must all be in the same conduit. A cable assembly, such as NM or UF, does not require conduit.

There are plenty of other things you need to know as well, more than any of us can remember to tell you in one sitting. You won't get it right if you don't do enough work ahead of time.
 
  #33  
Old 11-01-05, 09:28 AM
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Join Date: Sep 2000
Location: United States
Posts: 18,497
A subpanel does offer some flexibility, but it brings in a whole additional set of complexities that we haven't even begun to deal with yet. It strikes me that this project is not lacking in complexity already.

Permits have been mentioned several times, but I really think you need one, for your own protection. It will add a bunch of hoops you need to jump through, but each of those hoops increases the safety of your installation. We can give you lots of advice, but we can't look over your shoulder like the inspector can.
 
  #34  
Old 11-01-05, 09:35 AM
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Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,342
Originally Posted by thylantyr
I would like to run three #2 cables for this, two hot,
one neutral, if the cable is flexible enough for me to
squeeze through the framing. Someone mentioned it
has to be in conduit, is that one cable per conduit or can
I bundle all three cables inside one larger conduit? Or
can I pick one of those two options? Would this be THHN
cable? Does it come in different color sleeving or is it
all in black?
1) Subpanels must have four wire feeders, not three (hot/hot/neutral/ground). If you use THHN conductors, then they must be in conduit for the entire run from the main panel to the subpanel. If your locality allows it, you can use NM style or SER style cable assemblies to feed an interior subpanel.

2) If you install a 60A subpanel, you need to feed it with #6,#6,#6,#10 (black/black/white/green) THHN in 3/4" minimum conduit or 6/3 NM-B cable. If you decide on a 100A panel, you need to feed it with #3,#3,#3,#5 (black,black,white,green) THHN in 1-1/4" conduit minimum or 2-2-2-4 SER cable or 2/3 NM-B cable. I'm talking all copper conductors here, the gauges would be all different for aluminum. If you choose to run conduit, I would not run less than 1-1/4" so you always have the option of increasing to 100A.

3) The grounds and neutrals must be isolated in the subpanel. Meaning, you need to remove the bonding screw or strap in your subpanel and purchase an add-on ground bar kit. The instructions that come with the panel

4) The subpanel does not need a main breaker, although having one is optional.

5) You should get a permit and electrical inspection of this work.
 
  #35  
Old 11-01-05, 10:02 AM
thylantyr
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Posts: n/a


Thanks for the good stuff.

3) The grounds and neutrals must be isolated in the subpanel.

The reason for this is because? -> when there is an
equipment short they want the return path to go
directly to the main panel via that dedicated ground cable
and not back through the subpanel neutral cable even
though the ground and neutral cable are physically
connected at the main panel ?

One conduit with four cables sounds like a good idea
vs. running tons of smaller cables. I'm assuming it's
normal to drill a 1.5" hole in studs to get this conduit fed?

I'm also assuming building code would require this
conduit to be tied down to studs instead of just laying
there in the attic ?

When the #3 or #2 wires are fed to the main panel,
they connect the hots directly into the breaker that
feeds the subpanel, in this case perhaps a 60A - 100A
breaker?
 
  #36  
Old 11-01-05, 12:03 PM
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Location: United States
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The reason is to keep current off of the grounding wire between the panels except in the case of a fault.
 
  #37  
Old 11-01-05, 12:43 PM
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Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
A Sub-panel ( S-P ) can be any "size", where size is the # of circuit-breaker (C-B) positions, as long as the amp-rating of the panel equals or exceed the rating of the C-B that protects the Feeder Conductors.

If your are considering Non-metallic cable which is routed under/over joists , these are the pertinate Code Articles--

(C), Un-finished basements--- " ------ it (iS) permissible to secure cables not smaller than (#6) directly to the lower ( bottom) edges of the joists"

Accessible attics, 320,23------"Where run across the top of joists, the cable shall be protected by guard-strips" This means the cable would be laid between two 2x4's.

As to Grounding concerns in the S-P, many panels are now equipped with an Isolated-from-Ground Neutral terminal bar, and a seperate terminal bar for the connection of Grounding conductors.
 
  #38  
Old 11-01-05, 01:21 PM
thylantyr
Visiting Guest
Posts: n/a
A few years back, the airport did free home improvement
projects for the surrounding neighbors as a way to bribe
'us' into voting for their airport expansion which means
lots of bigger planes and noise. It was a big project.

Basically, they installed double pane windows, new
solid core doors, free air conditioning with new heaters,
and if needed, more insulation. The idea was to keep
noise down when all windows/doors were closed.

When they did this, they upgraded the main electrical
panel with the 240V/125A service. A box with a dual
125A breaker and 16 free slots. I have no idea if the
wires from the pole were upgraded, I doubt it.

This is what the CB power distribution looks like;

****
CB 1 & 2 - 220V, 40A - oven [one outlet]
CB 3 & 4 - Air conditioning/heater [heater = gas]
CB 5 - family room, garage, kitchen counter, fridge,
microwave, dining room, dining room lights
CB 6 - garbage disposal only
CB 7 - kitchen lights, kitchen counter, garage door opener,
tablesaw circuit.
CB 8 - Three bedrooms, 2 bathrooms, living room
CB 9 & 10 - 220V, 30A - Dryer [one outlet]
CB 11 - Family room
CB 12 - Washer only
CB 13 - free slot
CB 14 - free slot
CB 15 - free slot
CB 16 - free slot

****

The house was remodeled 15 years ago, hence the
wierd wiring schemes seen on CB5, lots of stuff.

Tid bits;
1. The oven rarely gets used.
2. Two fridges used.
3. Dryer used alot.
4. AC or heater used alot, but heater is gas.
5. Tablesaw only used for DIY projects.
6. The last heavy hitting item is the microwave.

When the home theater is complete, the circuit
on CB11 may never get used, so that will be 5 free
slots.

///

Based on this data, a dual 100A breaker could be installed
in two free slots [lets say slot 15/16] which in turn feed
the 100A subpanel right?

If you decide on a 100A panel, you need to feed it with #3,#3,#3,#5 (black,black,white,green) THHN in 1-1/4" conduit
I think that is the plan. But I'm thinking that I would
like to run #2, #2, #2, #4 THHN only because it's alittle
overkill. You don't get code violations for using thicker
wire in a smaller wire scenario?

////

I went to the home center to get a visual on all this
'stuff'. I saw a Square D 100A panel with six CB slots.
Looks like a nice fit for my narrow wall. yay/nay ?

re: Conduit.

Do you run the flexible conduit the full run from main
panel to sub panel or do you install stiff pipe at the panel
too then connect the flexible pipe to the stiff pipe?
 
  #39  
Old 11-01-05, 01:59 PM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,342
Originally Posted by thylantyr
Based on this data, a dual 100A breaker could be installed
in two free slots [lets say slot 15/16] which in turn feed
the 100A subpanel right?
Correct.

I think that is the plan. But I'm thinking that I would
like to run #2, #2, #2, #4 THHN only because it's alittle
overkill. You don't get code violations for using thicker
wire in a smaller wire scenario?
Nope, just wasted cash. The only advantage to thicker wire is less voltage drop under heavy loads; that may be worth the extra money to you.

I went to the home center to get a visual on all this
'stuff'. I saw a Square D 100A panel with six CB slots.
Looks like a nice fit for my narrow wall. yay/nay ?
That would be acceptable. Usually, I recommend a subpanel with a lot more slots than you think you will need. Personally, I wouldn't install a 100A 6 slot panel, but at least a 12 or even more.

Do you run the flexible conduit the full run from main
panel to sub panel or do you install stiff pipe at the panel
too then connect the flexible pipe to the stiff pipe?
The typical conduit for this job would be 1-1/4" PVC schedule 40 rigid. I would not recommend flex unless you absolutely must use it. You will find it very frustrating trying to get the thick conductors through more than a couple feet of flex. There are a myriad of pre-made fittings available for PVC conduit, and it is pretty cheap.

Conduit tips:

1) Assemble the whole conduit, let it cure, then pull the conductors in. Wet PVC cement melts wire insulation.

2) Minimize the number of bends. Code requires a pull box (or LB fitting) between each 360 degrees of bends. It would be very difficult to get these conductors through even 3 bends though.

3) Use a generous amount of a pulling lubricant, available in the electrical aisle.

4) Get a buddy to help; pulling wires into conduit is almost always a 2 person job.
 
  #40  
Old 11-01-05, 02:42 PM
thylantyr
Visiting Guest
Posts: n/a
That would be acceptable. Usually, I recommend a subpanel with a lot more slots than you think you will need. Personally, I wouldn't install a 100A 6 slot panel, but at least a 12 or even more.


Due to space restrictions, the box I found at the home
center is a Murray box, 125A with 8 slots, almost a perfect
fit between my 2x4 studs and it has a door.

A trip to the electric store is next.
 

Last edited by thylantyr; 11-02-05 at 08:37 AM.
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