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 1 response by gs5556

Don't add up amps, it's not the way its done. I count 5 circuits for audio, one for lights and one for AC. Usually you assign 360 VA (watts) to each receptacle plus air conditioning plus lights. The AC (11 amps at 240 volts) is 2,640 VA. The lights are 1,500 watts at most. That adds up to 5x360 + 2,660 + 1500 VA = 6,000 VA. That's only 25 amps because you're bringing in 240 Volts to the subpanel. You're barely going to draw half that under normal circumstances.

Even if you maxed out all circuits at 1,800 VA per dedicated line, that's still (5x1800+2640+1500)/240 or 55 amps at the ridiculous most you can possibly plug into.

Use a 100 amp subpanel with a 60-amp main breaker. At the main panel in the house, pop in a 2-pole 60-amp breaker and run the appropriate wire size (use 100-amp #2 wire @ 60 C) with the appropriate feeders, mind your grounding, and you'll be fine.

Inside, use 20-amp breakers for the receptacle circuits, 15-amp for the lighting circuit and check the manufacturers literature for the maximum breaker size for the AC unit (important at 240 volts).

Finally, put trust only in your electrician. Good luck and have fun towards your new project.

BTW - you'll have enough power this way for a well-stocked woodworking shop. Would add a ton of value to your house.