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danielrg 04-25-2012 04:52 PM

Elaborate Plan for wiring my theater lighting
4 Attachment(s)
This is kind of a complicated question, but I think I have figured out how to do it right. I wanted to run it by some folks here before going to the city code enforcer. See the attached diagrams for details.

I am planning a fairly elaborate lighting scheme for my home theater area, mostly because I plan for the theater automation to be a hobby for me. (I'm an electrical engineer)

I want to have banks of lights that I could later choose to group differently onto dimmer switches. For example, I have six can lights. Some people I have talked to think I should dim the front four together and back two separately. Some think I should dim the front two together and back four separately. Some say I should dim them all together.

So I decided I'd run each group of two cans to a junction box, run the switches to a junction box, and then wire the switches to the lights in the junction box - then I could later change it if I decided it should work differently. In addition, this would keep the junction boxes the dimmers were in free from extra wires, since I plan to buy nice dimmers that are fairly deep and would take more space in the switch boxes. And if I find that using switches differently would make it more intuitive, I can change which switch controls which lights easily after the fact. This would also allow me later to possibly control the lights with an automated system.

There are some track lights and rope lights, as well as a couple receptacles that would all come back to the junction box where they'd be connected to the switches/dimmers.

I am bringing in power from two circuits to balance the lighting. I plan to put some of the lights on one circuit and some on the other. The second circuit has some other stuff on it already, so it has less load left over, so most stuff will go on the first circuit.

Also to save on wiring and make running wire easier, I was planning to use 14/3 wiring where possible. Any given 14/3 wire would always be connected to only one of the circuits (no shared neutrals).

The attached files show my exact plan for each circuit. Note they both share the junction box in the upper right corner of the pictures, they also share the switch banks. This allows me to decide which switches control which lights, as well as decide which lights will be powered on which circuit to balance them properly. Note that the track lights are each 2 circuit track, that's why I'm running 14/3 to each.

See the attached files for circuit #1 and circuit #2

I am running 14/3 NM to the switches. I was planning to have two switches share one 14/3 cable. I am also running 14/3 to each group of two light groups that I want to control separately.

I've also attached a diagram from the perspective of the junction box.

I also attached an example circuit on how I plan to use the 14/3 wire.

Here are some other decisions I made:

- The junction box will be PVC 8x8x4 (256 cu. in.) All the wires coming into the box add up to 70 cu in. so the box should be plenty large.
- All the grounds from both circuits will be tied together
- The neutrals for both circuits will always be kept completely separate (NO shared neutrals)
- No 14/3 wire will ever carry power from more than one circuit (this would violate the shared neutrals anyway)

Even though this is kind of elaborate and for hobby, I want to be sure to do it safely and up to code. Does anyone see anything wrong with my plan?



gregzoll 04-25-2012 05:46 PM

Just pull all 12/2 & 12/3 for everything. Unless you know exactly to the T what the loads will be for each lighting circuit, the #12 runs of Romex will give you breathing room. Also use a sub-panel for this space, because you will thank me later, when you actually realize the shear number of circuits you will need for this space alone.

curiousB 04-25-2012 05:46 PM

You might want to consider EMT conduit for this and run all the fixtures back to a central junction box in a utility room (or under an access panel). EMT is a bit of a pain for the initial install but is fabulous for changes down the road because you can fish additional wires in the tube or change pairing of fixtures to control element. Bending is pretty easy for 1/2" tube and you save a bit on wire as you don't need NM cable nor do you need a ground wire (tube acts as ground).

It sounds like your needs may evolve over time so keeping you options open is always good.

Jim Port 04-25-2012 05:57 PM

ENT would offer the same ability to make changes as EMT and is easier to work with. It would require a grounding wire.

JulieMor 04-25-2012 06:09 PM

I did a boardroom for a major corporation as part of their new corporate office. We installed Lutron's GRAFIK Eye system to control lighting, shades and give them the ability to create "scenes" at the push of the button. The wall switches were simple 4-gang boxes but could do everything you are looking to do here and more. These systems are not cheap but they are very impressive. Lutron makes them for residential applications too. I'm not sure what you are planning to spend.

I'm seeing banks of switches on the wall that could become hard to remember what controls what, even for the installer. In my basement I installed 6-gang switches and after 25 years I still have trouble remembering which switch controls what. You have 13 switches. You may want to look at other options. Maybe other manufacturers have other less expensive room controls then Lutron's.

If you do decide to use separate switches, you can go up to 6 switches in a box and still find coverplates. To give you extra wiring room in the boxes, you can use masonry boxes that go up to 3-1/2" deep. Garvin makes solid ones up to 6-gang but you can get gangable boxes too.

I see one 3-way dimmer. Most 3-way dimmers only allow dimming control at one location. The ones I installed when I built my home wouldn't dim if the switch at the other end was in the wrong position. I later replaced those with Lutron Maestro dimmers and now have complete dimming control at both switches. Again, not cheap but I love having the control.

It looks like you're running romex or some other flexible wiring rather than installing conduit. (conduit is code here) I don't see anything wrong with how you're wiring things but you'll have a lot of fun keeping track of what is what. You may want to look into wire markers or just use a felt pen to mark all the wires as you install them.

The only thing that concerns me is you didn't give the loads, existing or new. You have (2) 15A circuits and you are adding a lot of load to them, unless your lamps are LED. You should get an amp probe and turn on everything on the existing circuits and amp probe it so you know your maximum load. Code says total load should not exceed 80% of the breaker rating. 15A breaker = 12A max. load. You'll then need to calculate the added load and make sure you don't exceed the 80% rule. And no, I won't tell you there may never be a time when everything is on so you can stretch the rule! :no:

Your plans are certainly ambitious. The lighting should be pretty cool. When you're done, post some pics of the new room and all the different scenes you can create. I'd love to see the finished result.

danielrg 04-25-2012 06:28 PM

I have done a load calculation for each circuit.

The recessed lights are rated max 90 watts. I assumed 100 watts each. Sconces are rated 75 watts I assumed 100 watts each. I assumed 75 watts for each rope light - they should be more like 30 watts. I assumed 100 watts off each dimmable receptacle. I assumed 100 watts per circuit on the track lighting - I expect 50 watts per circuit.

All in all, I show 1400 watts on Ckt 1, and 1300 watts on Ckt 2. I can go up to 1440W with each 15 Amp circuit, right?

I really don't want to run 12 gauge - costs more and harder to run, I'd rather add a 3rd circuit. I may run an extra 14/2 to the panel just in case these ever overload.

Running conduit sounds like a neat idea, I'll have to think about if I have the time or inclination...

Thanks so far for the input - any other ideas?

gregzoll 04-25-2012 06:42 PM

Actually when you compare the costs, using 12 will end up in the long run cheaper. Never go with cheap and lower end, especially with electrical. If you look at most commercial lighting installs, all they use is #12 for lighting.

JulieMor 04-25-2012 07:11 PM


Originally Posted by danielrg (Post 907548)
All in all, I show 1400 watts on Ckt 1, and 1300 watts on Ckt 2. I can go up to 1440W with each 15 Amp circuit, right?

I really don't want to run 12 gauge - costs more and harder to run, I'd rather add a 3rd circuit. I may run an extra 14/2 to the panel just in case these ever overload.

Running conduit sounds like a neat idea, I'll have to think about if I have the time or inclination...

Thanks so far for the input - any other ideas?

You mentioned one of the circuits you planned to use already has a load. Do your calcs include the existing load? If so you're OK. And yes, 1440 watts for a 15 amp breaker is max.

You don't need #12. #12 is rated for 20 amps. You don't have 20 amp breakers and you don't have any problems with voltage drop (none of your runs are long enough) so #14 is fine.

If you decide to go conduit, you'll need to consider conduit fill. If you pull in #14 THHN you can get a lot of wires in a 1/2" conduit but code restricts you to 9 current carrying conductors. Grounds and neutrals are not included in that count. Usually local codes don't require a ground in an all metal raceway system.

Bending pipe is pretty easy if you have a decent mechanical aptitude. The artistry comes in the planning... and using a tape measure and a level. :whistling2:

When you run conduit from can to can, you run different switch legs through them. The only problem comes if you want to access it later. You have to remove the can first. It's kind of a pain to access the box but I've done it many times. And when properly run, conduit looks so much better.

JulieMor 04-25-2012 07:20 PM


Originally Posted by gregzoll (Post 907560)
If you look at most commercial lighting installs, all they use is #12 for lighting.

The reason for that is local codes require it. The lighting loads still never exceed what a 15A breaker can handle. The big difference in commercial applications is distance from the panel. I've pulled runs over 300'. As the run from the panel gets longer, the distance creates a drop in the voltage. In order to compensate for that, you move up a wire size (or two).

gregzoll 04-25-2012 07:27 PM

Juliemor, nothing to do with codes. It is due to when you get to finally doing the lighting, you find out that the 15amp circuit with #14 will not work. At that point you end up either pulling more circuits, or have to rup it all out and start over again. Take it from someone who has experience this and knowing what the OP is doing, going with #12 for all runs, regardless if it will be 15amp or 20amp, they will quickly realize it, if they take time during the planning phase to look at the big picture.

Electronic lighting systems are not forgiving when you do it wrong at the beginning.

a_lost_shadow 04-25-2012 07:31 PM

Do you know what version of the NEC you're under? 2011 requires that you pull a neutral to the switch location in most cases.

JulieMor 04-25-2012 07:47 PM

Gregzoll, I really don't understand where you're coming from.

It is due to when you get to finally doing the lighting, you find out that the 15amp circuit with #14 will not work.
Are you talking about dimmed lights? Flickering? Please explain.

I've been an electrician for 38 years. The wire gauge and the insulation determine the maximum amperage of a conductor. 14ga wire is typically rated to handle 15 amps, unless there's some funky insulation on it. As insulation technology has improved the amperage ratings have gone up.

Usually, in residential, 15A is the smallest breaker allowed and 14ga is the smallest wire allowed. In this application, he's following the 80% rule so I can't see how 14ga wire would ever be a problem.

I know a lot of guys like #12 but most of the guys I know like that have never worked on a residential job in their lives. While most of my time has been on commercial jobs, I've done my fair share of residential work (it used to be required as part of the IBEW apprenticeship training). I've never seen a lighting problem using #14, as long as the 80% rule is followed.

danielrg 04-25-2012 09:36 PM


Originally Posted by a_lost_shadow (Post 907602)
Do you know what version of the NEC you're under? 2011 requires that you pull a neutral to the switch location in most cases.

Double thanks for making this point. Just the kind of tip I was looking for. Now that I think about it I remember looking at some of the fancier dimmers or other automation options and many of them require a neutral connection.

I think may at least run an additional 14/2 to each of the switch boxes so there is a neutral available, or two neutrals (with the black marked as neutral) if I divide switches between circuits.

Better yet, I should at least run conduit from the junction box to the switch boxes.

My thoughts about other comments:

I'll have to think about running conduit and/or moving to 12 gauge for the whole thing. I have been running 12 gauge for all my outlets in the basement, but was going to stick to 14 gauge for the lighting - now I think I may reconsider-- then I can move to 20A breakers in the future if desired.

I did consider all loads on these circuits - they are both completely new circuits (no loads other than those shown in the diagrams) so there is no existing 14 gauge wiring to worry about overloading.

Many thanks to everyone for the comments! :thumbup:

jbfan 04-25-2012 09:49 PM

The GRAFIK eye would be a good choice, and the cost will be close or less than having 13 dimmers scattered around the room.

Juliemor, what 80% rule are you talking about?
There is not an 80% rule in residential.

danielrg, if I'm not mistaken, receptacles can not be dimmed.

You can go up to 1800 watts on the lighting circuits on a 15 amp breaker.

You also have to remember that any junction boxes need to remain accessible.

danielrg 04-25-2012 10:13 PM

1 Attachment(s)
I have reworked the junction box diagram with neutrals.

I decided to run the power in the 14/2 and have the neutrals in the 14/3 be neutrals again.

The way I have it figured, I have "both" wires connected to the same circuit's hot, but might connect one of them to the other circuit's hot if I decide to control lights on separate circuits with two of the switches. Is it against code to carry the hots from separate circuits in the same NM wire? What about carrying the neutrals from two separate circuits in the same NM wire? Should I just run two 14/2 just in case?

If I do conduit to the switch boxes, then I don't have to care- I can just run what I need...

I'm still considering using 12 gauge, but I'm not going to update all my diagrams with it :whistling2:

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