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How to disperse avail. amperage?

I am going to soon be the proud papa of a designated listening room. Yes, it is the culmination of a 30+ year dream, but that's another thread. My question is : how exactly do I "divvy-up" the available electric into the room? I am converting a 13' x 18' detached garage which started out as uninsulated studs on the interior only shell, on a concrete slab. The exterior walls are approx 3/4" planking (built in the 1940's) with recent vinyl siding. I built a shed to house all the important stuff and ditched the rest. I had a new roof put on, as well as new leaders and gutters. I also had a side entrance door installed. I plan on removing the worn main 'big' door and removing the interior tracking for it, then i nstall a new dummy door, permanently affixed. Inside that I'll stud out an interior shell wall , then insulate and drywall it. I am well on my way with much of this already. I'm having an electrician come today to discuss running a 125amp sub panel from my main house's [recently upgrade] 200amp panel, out to the garage. this will include an 18" trench to run the cable, and I'll probably add a "cable box" cable too...When I have the box installed it'll be 125 amps. I'm expecting the main breaker on the house side of it to probably only be 100 amps? as well as the main breaker on the sub panel to only be 100 amps too... mostly because the 100 amp breaker is 1/3 the $300 cost of the 125 and I can't imagine I'd be drawing that much current all at one time?
I would like to have a separate breaker for "all lighting", as I plan on using dimmer switches and a reasonably extensive amount of light.
I will also be installing at a later time, when $$$ allows, a ductless A/C & heating system that can use a 15amp service (draws 11amps max). I was thinking it would be nice to actually provide a 20 amp line to this if I had the extra available.
I want a dedicated line for my analog pre, turntable, and analog misc (my electronic crossover)
I need a dedicated digital (multi players, Dacs , jitter boxes, SACD, etc
And since I am TRI-amping my speakers I need a dedicated for my tubed monos
A dedicated for 2 sub amps
A dedicated for my mid/tweeter amp
At 20 amps for each, except the lights,this adds to 120 plus the lights. Can I use a 10 amp on the lights for a total of 130 and be OK? Should I lessen the digital or analog only to a 15A for one of them? Any combination you can imagine would be a helpful suggestion. Thanks! Happy Lissn'n
lissnr

Showing 6 responses by jea48

jea48
4,672 posts
 
Lissnr,
You did not mention how far from the house the garage is.
Distance from the house main electrical panel, to the new audio room sub panel? You may need to take into account voltage drop.

You stated the new sub panel feeder will be buried 18" below grade.
Direct burial cable or PVC conduit with single conductors?

I would recommend PVC conduit over direct burial.

Copper or aluminum feeder conductors?
Copper will cost you an arm and a leg.....

And I hope you are not thinking of an isolated dedicated equipment ground rod.

The equipment grounding conductor shall occupy the same raceway or cable as the feeder conductors and shall terminate in the same panel as the feeder conductors, NEC.

I'm expecting the main breaker on the house side of it to probably only be 100 amps? as well as the main breaker on the sub panel to only be 100 amps too... mostly because

First off you do not need a main in the sub panel, that is unless your local code requires it. If your local code does not require a main then all you need is a main lug only panel.

The sub panel and sub panel feeder will be protected by the breaker at the main electrical panel for the new feeder.

As for the sub panel what brand are you looking at?
I would use a panel with copper bus. If you have the money I would go with a Square D NQOB panel board. The bus is copper and the breakers are bolt on.

I'm expecting the main breaker on the house side of it to probably only be 100 amps? as well as the main breaker on the sub panel to only be 100 amps too... mostly because the 100 amp breaker is 1/3 the $300 cost of the 125 and I can't imagine I'd be drawing that much current all at one time?
I do not believe you could install a 125 amp breaker in the main 200 amp electrical panel anyway. It might fit but the panel is not approved for that large of a breaker.
Curious, did the electrician say he could?
jea48
4,672 posts
 
The overall [cable length] distance from main box to sub panel will be about 50'
That's a far cry from 110' you posted earlier......
If the run is only a total of 50' then #4awg copper should be fine.

As for the separate ground...I'll ask my electrician (who came highly recommended from a contractor friend of mine)and who claims to be fully licensed...what I will do there.
Ya, post back his response if you would.

The Hubbell I/G outlets can still be used anyway, yes? Even if they're simply grounded back to the sub panel's standard grounding bar?
Unless you just like the orange color of the receptacle why did you spend the extra money for isolated ground receptacles?
Isolated ground receptacles are used in commercial and industrial facilities where EMI noise on conduit, metal studs and steel are a problem. I assume you will be using wood studs with MN-B cable and plastic rough-in boxes.

Essentially the non IG Hubbell will work just as an IG ground type in your instance.

For the Power Amp/s I personally would go with the Hubbell HBL8300H ("H" stands for non plated)
jea48
4,672 posts
 
I would recommend "Lutron" Dimmers!
jea48
4,672 posts
 
I didn't even realize that the ground wire was supposed to return to connect to the main house panel!!
Yes it does, as per NEC.

I thought we were going to run a ground wire from the sub-panel via a #6G bare copper wire to an 8'-10' pole hammered into the ground at least 8' from the garage and that was THE ground..
Have your electrician read NEC 2005 250.54 Supplementary Grounding Electrode. Page 70-103

Do I still do that, even with the #6G returning to the main house panel [underground and in the soffit] along with the 2 hots and 1 neutral #2G's? BTW, if I use a PVC tube to encapsulate the underground wires will that be a different type of wire/can it be the same as the "in-house/soffit type" as compared to an "underground feeder cable"? I was checking prices on #2AWG copper cable and we're up to at least $2.50 per foot! Does that mean 65' + 45' = 110'x3 runs (2hot,1neutral) for a total of 330' x $2.50ea = $825 plus the 110' of #6 ground @ $xx? per foot? WOW...

I said it would cost you an arm and a leg.....
You could use aluminum. You would need to increase the size to #1 awg, and the equipment ground wire to a #4 awg.

The wire from your main electrical panel in your home to a junction box mounted on the house above the earth could be insulated THHN/THWN copper installed in 1 1/4" EMT metal conduit. You could use 1" EMT per code but trust me it is a bitch pulling 3 #2 and a #6 in 1".... From the JCT box through the earth to the new sub panel XHHW insulated copper wire in
1 1/4" PVC conduit.

Also, when you say the dedicated branch circuit will have 1hot,1neutral,1gnd... you are referring to the individual wire of 12/2 or preferably 10/2 Romex which attaches to the outlet? When you say "No sharing of neutral" what does this imply?

Multi wire branch circuits.

You can have two 120V separate branch circuits sharing the same neutral.
Each Hot conductor must be connected to opposite Lines, legs, in the sub panel. One on L1 the other one on L2. With this wiring configuration only one neutral conductor and one equipment grounding conductor are required. Two separate circuits..... But not two dedicated circuits.

I was thinking of running 2 x 5362 Hubbels next to each other 9for a total of 4 plug in points0 per 20A dedicated line...
Sounds fine. Many will recommend using plastic rough-in boxes instead of metallic.
jea48
4,672 posts
 
I also bought the optional ISOLATED grounding bar for it.

Why? An isolated ground bar will serve no purpose. I imagine the panel enclosure will be mounted to wood studs and the branch circuit wiring will be NM-B cable. (Romex is an example of NM-B).

How does your electrician plan bonding the panel enclosure to the main electrical systems equipment ground? Is he going to install two equipment grounding conductors from the main electrical panel to the sub panel? One for the isolated equipment ground bar and one for the panel enclosure?

The most serious deviation from all our discussion is that because I'm only running a 70Amp main breaker (into the 125A panel) my electrician and the guys at the electric supply store told me 2G wire is way overkill and that 4G can handle 100A service so I shouldn't waste my $$$ on the 2G and just get the 4G... which, although I was hesitant not to continue with "over-overkill everything"... I decided to do the 4G.

NEC 2005 Table 310.16
#4awg 60 C is good for 70 amps, not 100......
Because of the distance from the main electrical panel to the sub panel I would have stuck with the #2awg minimum.

my electrician and the guys at the electric supply store told me 2G wire is way overkill and that 4G can handle 100A service

The guys at the electrical supply store are not electricians.

Did you ask to see your Electrician's Electrical License?

You are not installing an electrical service. You are installing a feeder and a sub panel. NEC does allow # 4awg for a 100 amp electrical service. But in most cases the service entrance conductors are less than 25 ft.

In your case the larger feeder wire is for voltage drop due to the air conditioning load, small refrigerator, as well as the dynamic demand your audio system's Power Amp/s
may present on the feeder. You want the voltage not to fluctuate with load changes as much as possible.

I also didn't skimp on the ground for it... while everyone told me the ground cable can be one size smaller than the main ones,


I think they confused the neutral, (The Grounded Conductor), with the equipment ground, (The Grounding Conductor).

NEC 2005 Table 250.122 Minimum Size Equipment Grounding Conductors for Grounding Raceway and Equipment.

70 amp breaker - minimum #8 awg copper.

I said go with a #6 but I think for an audio system a larger wire would probably be better.
jea48
4,672 posts
 
I'll let you know what my electrician says about the isolated grounding bar/from the I/G outlets. Thanks again.
Lissnr


It is a Myth that the earth has some mystical magical power that sucks RFI/EMI noise from an audio system.

Though I do not advocate lifting the equipment ground , no equipment ground for an audio system seems to be the best.

More and more audio equipment manufactures are building their equipment with double insulated AC power wiring thus eliminating the need for the safety equipment ground.
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