Theater electrical! Opinons please!

Discussion in 'Home Theater Projects' started by JohnGil, May 14, 2003.

  1. JohnGil

    JohnGil Stunt Coordinator

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    Hi all this will be my first post on this forum. I have been a long time reader here.

    I have a 12'W x 20'L concrete block detached garage. It has no interior framing accept the trusses which are built old school perfect pyramid so I have many options as far as proposed interior room hight. There is no electricity to it so basically I have a bare bones room to start with. I have been planning on developing this into a Theater room for years now and have finally started buy digging a trench and running conduit for the future electrical which will be my first step.

    So question at hand. If you were starting from scratch in this stuation how many breakers and what amperage would you use for your power.

    I will be using 3 B&K ST140 amp's, Panisonic Rp91 DVD player, and a B&K ref.20 processor pre amp, 3 klipsch fortes for LCR and Klipsch KG2's for suround and rear and 2 Klipsh SW12's. The projector will be determined latter but it will be a DLP or LCD. I intend to also have at least 1 butkicker shaker, lighting with dimmers, an alarm system and im sure Im missing several other items.

    I just want to get off on the right step and this is my first one after the internal framing which is a diff. issue.

    Thanks for any help you can provide.
     
  2. Ken-Ha

    Ken-Ha Extra

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    I am in the planning stage to turn a partial of my unfinished basement into a HT. The size of the HT will be 14X20. I am using 3-15AMP circuit breakers just for the HT Room.
    Best regards
    Ken
     
  3. MikeWh

    MikeWh Second Unit

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    John--

    My advice (worth 2 cents) is to just do the math-- add up the watts of all the A/V equipment, the lights, etc... and determine how many amps you'll need (amps = watts/volts). In the US, 120V is standard. Circuits are designed to carry a continuous 85% load, so for simplicity (and safety) the formula is approximately: amps = watts/100V.

    So a 15 Amp circuit can carry 1500W continuously; a 20 amp circuit can carry 2000W continuously. Figure out what you have and what you need from there. FWIW, I have a dedicated 15-amp circuit for A/V and another 15-amp circuit for all the lighting and wall outlets. Your mileage may vary. [​IMG]

    I highly recommend segregating A/V components onto a dedicated circuit, especially if dimmers are going to be used for lighting.

    I also highly recommend going to the local library and getting a book or two on household wiring. They are invaluable (and FREE!!), especially if you're unsure about something like circuit loads. I seem to remember a Time-Life one and a Reader's Digest Guide were both very good. If you plan on doing anything like a 3-way switch(for controlling a light from two different places in the room), then you definitely should read read read... [​IMG]
     
  4. JohnGil

    JohnGil Stunt Coordinator

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    Thanks very much guys for the advice. I'll read up and keep ya posted as the theater progresses.
     
  5. Chad Anson

    Chad Anson Second Unit

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    Also, FWIW, a 20-amp circuit is marginally more expensive than a 15-amp circuit. Even if you decide to go with a 15-amp circuit, I'd wire it with 12-ga wire so that you could go to a 20-amp circuit later if you need the additional capacity.

    Here's what I've got going to my HT and adjacent woodworking workshop:

    20A - for lighting - 3 cans, 2 track lights, 4 sconces
    20A - for equipment closet
    20A - for projector and subwoofers
    20A - for mini-fridge and dust collector in the woodworking room
    20A - for power tools in the woodworking room
     
  6. Drew Eckhardt

    Drew Eckhardt Stunt Coordinator

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    1. Stick to 20A circuits - they don't cost any more, and give you more capacity.

    2. Put the light circuit(s) on the opposite leg from the equipment circuit(s)

    3. I don't know where multiple circuits would be required. For example, my power amplifiers are placarded for 3240W - although power consumption at idle is just 225W, and the combination of reference level audio + other equipment is not enough to trip even a 15A breaker.
     
  7. Gary Silverman

    Gary Silverman Stunt Coordinator

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    I would bring a 60 amp 115/230 volt circuit out to your garage and terminate it in a small circuit breaker panel. That would allow for more flexibility and for any future expansion of the system. You may upgrade your system later on, add heat or a/c, or countless other possibilities.
     
  8. MikeWh

    MikeWh Second Unit

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    Drew-- Are you confusing total RMS watts/channel with line consumption? (3240W?) They're related, but RMS output per channel shouldn't be used when figuring A/C line amps.

    John-- FWIW, I did the math on these components. Some were max. guesses, based on their fused capacity:
    3 B&K ST140 amp's (155W x 3)
    Panisonic Rp91 DVD player (16W)
    B&K ref.20 processor pre amp (60W)
    2 Klipsh SW12's (100W x 2)
    A projector (400-ish)
    -------------------------------
    That's 1140W, or approx. 11.4A

    That doesn't include the buttkicker, if you're powering it separately.
     
  9. Leo Kerr

    Leo Kerr Screenwriter

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    I dunno; if I were able to do some serious work like this, I'd probably try to split stuff up, too.

    Projector gets its own circuit.
    Power amps get their own circuit(s) (as needed.)
    the main rack (dvd player, processors, tape machines, et cetera,) might get their own circuit (or they might be tied into the power amps? Not sure. Circuits are cheap in the long run.)
    "effects" like the butt-kickers, subs, et cetera, get their own circuit,
    and allocate at least 2 20a circuits for lighting.

    And, a good recommendation is to bring in a seperate sub-panel, and if at all possible, bring it in at 240v. Then do some "sensible" things like make sure of the two lighting circuits, they're on different phases, and make sure you have stuff on both circuits.

    Not that I've ever done any of this...

    Of course this brings up another point: how stable is your neighborhood's power? In my area, if an air conditioner kicks on within about a mile, we all see it in the lights. When I power up my Yamaha DSP-A1, all the UPSs in the house beep.

    Leo Kerr
    [email protected]
     
  10. MikeWh

    MikeWh Second Unit

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    There's absolutely no reason to split up circuits more than is necessary. As I've said, it's straight math and a simple Law of Nature (W=VxA). Nothing mysterious here. You plan your circuit based on the power you need and the different devices you have or may have in the future.

    The reason for splitting the lighting circuit off (I referred to a "dedicated circuit"; Drew referred to "the opposite leg") is because of interference from the dimmer switches. Transformers, motors, neon signs, fluorescent lighting, and heating coils are some of the common devices that should be separated from A/V equipment in order to minimize EMF interference and/or voltage drops that could negatively effect the performance of the electronics.

    Leo-- if anyone experiences problems with an A/C compressor kicking in a half-mile away, it's time to raise some stink with the power company. There's absolutely no excuse for that. And as far as UPSs going off in your house, Leo, by the pictures of your LCD Theater, I can see why that happens. It may be time to call in the power company to bring in some extra power. [​IMG]
     
  11. Ken-Ha

    Ken-Ha Extra

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    Mike, you are correct. I bought the "Wiring 1-2-3" from Home Depot. I believed they use even a lower number 1440 Watt per breaker. Like my case I am planning to install 3-15 AMP. circuit breakers. I figured when I am watching movies or TV, the lights will be either turned off or in a dimming mode. I think the HT hardwares that draw the most juice is front projector, e.g. the Infocus X1 consumes about 240 watt, which means 2 AMP.
    But then if someone needs an air-conditioner in the garage may consider to have the fourth circuit just for the sucker.

    Best regards
    Ken
     
  12. JohnGil

    JohnGil Stunt Coordinator

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    Well seems and sounds, like there are allot of options. I do like the idea that was given about having a box located within the theater room. Then breaking it up from there and having more options for future upgrades. I will need at some point climate control.

    My main concern is making sure all the wires are run before any sheet rock is done and having plenty of power and as little electrical noise as possible.

    Once again thanks for ALL of your input it is very helpful.
    I will document and take pictures of the wiring as I go and keep you all posted on the progress.
     
  13. MikeWh

    MikeWh Second Unit

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    John-- bringing a secondary breaker box out is actually ideal. I had forgotten it was an out building. Good luck.
     
  14. Leo Kerr

    Leo Kerr Screenwriter

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    My general opinion on far more circuits than required is actually a fairly simple reflex reaction from my day-job. We're always in dire situations trying to find enough power in certain areas of the building. This way, there's room to expand. Very likely, yes, the entire project could be done on perhaps as little as 2 20amp circuits. Maybe less - depends on how tight you were willing to squeeze. Splitting the lighting over two different poles is merely a safety issue - actually, no, it was a stupidity move on my part. You can't loose one leg of a 240v power feed into a residential area - not really; I'm more used to not real 240v power, but 208 off of 3-phase where you can loose one leg at a time. But having the lighting on two different circuits gives you a fall-back when a lamp blows out and takes the rest of the circuit with it. (There are certain kinds of light-bulbs that are very prone to doing this; being on the order of better than 50% of the time. Fortunately, they are rare in the consumer market.)

    As for my neighborhood's power, well.. our service was wired in in the early 1950s. The base service hasn't changed, even though the housing density tripled, and I don't think any of the houses in the area have 50amp mains anymore... (Can you believe that?! A 50amp main on the breaker panel?! Sheesh!)

    Curiously, the power company is happier to replace the transformers that explode on a regular basis rather than do a real fix.

    Leo Kerr
    [email protected]
     
  15. WarrenHH

    WarrenHH Agent

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    John, you might also consider using plastic conduit runs to boxes where you plan to terminate your speaker runs, and the run to your projector. That way when they come out with some new type of interconnect for the projectors, and or if you decide to use some new top secret brew of unobtanium/kryptonite speaker cables, you can tie the new cable onto the old, and pull one set out, while pulling the new run in. Use sweeps (gradual bends) not 90 degree bends or you will never get the wire through it.
    It might save you many headaches in the future.
    Also don't forget to run power in the ceiling at the front if you are ever going to use a powered screen, and some way of running power & cables to the floor near your seating for electric chairs, game cables, rope lighting for your riser, chair shakers, telephone, computer, whatever. Conduit is cheap now, worse later.
    I am in the midst of planning now to, for a new construction HT, so going through the same planning process you are.
    Best of luck to you.

    Warren Holm
     
  16. JohnGil

    JohnGil Stunt Coordinator

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    Warren, thanks for the heads on the conduit that prob. just saved me many headaches very appreciated.
     
  17. Scott Sabin

    Scott Sabin Stunt Coordinator

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    Warren,

    I'll add in another set of suggestions.

    First, since you have no power running to that out building, make sure you run a 4-wire feed - 2 hots, a neutral and a ground. Additionally, you will need to install a ground rod at your garage, and make sure you keep the neutral and ground buses separate in your sub-panel. This is different than how it is done in your main panel.

    Next, don't skimp on your service feeder wires to the garage. Since these wires will carry ALL of the current going to the garage, you don't want them to suffer from significant IR drop (voltage drop caused by wire resistance). Bigger sized wire has less resistance. While it is certainly within code to wire a 30A 240V circuit to your garage with 10/3 cable, you should strongly consider going to 8 ga if you think you will be drawing anywhere close to the max capacity.

    Regarding light circuits, two points to mention. One, put your lighting on the opposite pole as your audio equipment. Dimmers are notoriously noisy and if placed on the same pole, can somtimes cause audible noise. Second, know that a dimmed lighting circuit draws the same power as a fully lit circuit. The dimmer itself wastes the extra power that doesn't go to the bulb. The only thing a dimmer "saves" you is light output, and bulb wear.

    If your garage is considered living space, you don't need GFI outlets, but otherwise you do. Note that you can daisychain GFI protection, so you only need 1 GFI outlet at the start of the chain. Also make sure any GFI outlets are rated properly for your circuit (GFIs come in 15A and 20A ratings).

    Finally, know that you can plan on utilizing 100% of the rated capacity of general use circuits, not 80%. This is simply what the NEC requires though, and I would advise against planning on utilizing 100% of a circuit's capacity. General use circuit are for lighting and the general use plugs located throughout your room. Speaking of which, you must have a receptacle every 12' of wall space for walls which are at least 2' long, and within 2' of every corner. Home theater equipment is considered general use, but I would shoot for more like 50% utilization on each circuit.
     

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