Low Voltage or Line Voltage Lighting - How to Choose? - AVS Forum
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post #1 of 19 Old 05-10-2012, 10:17 PM - Thread Starter
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I couldn't find what I thought was a really good thread on low voltage vs line voltage lighting for cans/accent lighting. This is what I have read so far:

LINE VOLTAGE LIGHTING

PROS:
  • Easy to know how to wire
  • Doesn't need a transformer
  • Less expensive to start
  • Uses less expensive easier to find dimmers

CONS:
  • Doesn't have as crisp a color as most low voltage lighting
  • Filaments are more fragile, lights don't last as long
  • Lights don't come in as many colors and beam widths

LOW VOLTAGE LIGHTING
This is pretty much the converse of the above list, but I'll put it down for verbosity.

PROS:
  • Can find almost any color or beam width - more bulb options
  • Bulbs can be smaller and put out more light
  • Focus of light is better
  • Bulbs have stronger filament and usually last longer

CONS:
  • More expensive than line voltage initially
  • Uses transformers - either magnetic or electronic - and you have to find the right dimmers
  • Transformers in each light (or an outside transformer) mean more parts to break
  • Buzzing, especially when dimming, is more likely to be a problem

So, for a home theater, when would you choose low voltage lighting? Is there a good reason to? Dimming is a big thing in theaters - how do you get low voltage lighting and make sure it doesn't buzz? Does line voltage ever buzz?

I would think there would only be rare cases where you'd want to go low voltage:

- very specific task lighting
- very specific effects on walls or screen
- artistic lighting

Otherwise, it doesn't seem like it would be worth it. Screen wash lighting for example - could that be a gray area? For some, line voltage flood halogens is plenty while others may prefer a narrow beam low voltage whiter lamp?

I am thinking this - assume line voltage unless you can convince yourself you must have low voltage. Is that a good approach?

Electrical engineer by education. Currently a system engineer. I like home automation, theaters, and blinking lights.
Someday it'll be more of an actual hobby - if my employer would ever let me go home!

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post #2 of 19 Old 05-11-2012, 03:23 AM
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Wow! Electricity in Salt Lake. What an advancement! (I'm from Utah so I have poetic license.)

Line Voltage vs Low Voltage isn't really the best selection criteria. What you should be doing is selecting the fixtures/lamps based upon what you want to achive from a lighting design criteria. Most lamp colors are available both ways. In the ideal world, you'd want all lamps to be 6500 Kelvin but that's not likely to happen outside of RGB LEDs or dimming fluorescent lamps (they are also the only lamps which maintain color temperature when dimmed.)

"Buzzing" can be a consideration; however, using quality transformers (not necessarily 'expensive') and staying away from cheap, poor quality dimmers will prevent that issue. It is also worth pointing out it is more often the filament in the lamp which creates the buzz.

Dennis Erskine CFI, CFII, MEI
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post #3 of 19 Old 05-11-2012, 05:39 AM
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I went with low voltage puck lights due to space constraints. Due to duct work in my soffits, there isnt enough clearance for cans. I bought a 250w magnetic transformer for around $100 so i could dim them with my Grafik Eye. Im pretty sure with a magnetic transformer you could use most other 'standard' dimmers also. The transformer does buzz very slightly, but only when dimming. I built an enclosure for it out of 3/4" plywood and now I cant hear it at all, ever. I know the instructions said not to enclose it, but it has a fair amount of air space around it and it doesn't ever get very warm, probably because Im not drawing anywhere near its rated wattage. Cost wise, for me it was actually slightly cheaper to use the low voltage pucks. Originally i was going to use wall sconces, that would have been around $200 for the room. 10 low voltage puck lights and a transformer came in at around $150


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post #4 of 19 Old 05-11-2012, 08:56 AM - Thread Starter
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Running line voltage circuits is straightforward. But let's say I went low voltage for some reason or another.

1) Would it be better to:
  • buy a separate, high quality transformer, house it in my equipment closet, and run low voltage wiring to the lighting
OR
  • buy lighting with transformers built in?
2) Which are better in most cases? Electronic or Magnetic transformers?

3) How much thicker does my wire need to be for low voltage? I heard the gauge depends on the AMPERAGE, which will be much higher for 12VAC vs 120VAC (10x or so AMPs for the same wattage lamp?)

4) Do I dim BEFORE or AFTER the transformer? I would assume before..

5) What kind of dimmer do I look for for either a magnetic or electronic transformer?

6) For track lighting - is it better to have a line voltage track and heads with the transformers built in? What about if I am dimming?

Thanks in advance! Folks here have the best knowledge anywhere IMHO

Electrical engineer by education. Currently a system engineer. I like home automation, theaters, and blinking lights.
Someday it'll be more of an actual hobby - if my employer would ever let me go home!

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post #5 of 19 Old 05-11-2012, 10:09 AM
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1. i could be wrong, but i think pretty much anything with a built in transformer is going to be of the electronic variety. This is why I went with a separate transformer so I could use a magnetic one.

2. Electronic and magnetic transformers use different methods of dimming a light. I dont recall all the technical aspect of it though. Basically, if you use something like a grafik eye or standard dimmer switch, you cant just plug in an electronic transformer. You'd need and Electronic low voltage interface. This is not required for a magnetic transformer. The ELVI for a grafik eye was about the same cost as a magnetic transformer when I looked. If your not considering a grafik eye, this may not be important to you.

3. I didnt research this much and just used 12 gauge outdoor low voltage wiring. It stated on the package that it was to be used for certain distance of a run. Its also thicker than what came with the lights originally, but that was intended to be for a shorter run. The 12 gauge wire was reasonably cheap too. Keep in mind that with some low voltage systems, like my puck lights, the wiring is not to be permanently enclosed in a wall. this may vary depending on the fixture and wiring used. My wiring will be accessible through removable panels in the soffits.

4. dimmer goes in before the transformer. however, some low voltage lighting kits have built in dimming capabilities, but it cannot be controlled from something like a grafik eye or standard wall switch.

5. with a magnetic transformer, pretty much any standard dimmer switch should be fine. or use with a grafik eye. other autmated lighting systems like insteon might work too.

with an electronic transformer, i believe you need a dimmer designed for it or a special interface adapter.

6. i dont have much experience with track lighting, sorry. But Id say the same points regarding dimming a magnetic vs electronic transformer still stand.


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post #6 of 19 Old 05-11-2012, 10:11 AM
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I should also clarify. The primary reason I went with low voltage lighting was due to space constraints. My low voltage puck lights are only an inch thick. If not for that, Im sure I would have saved myself the trouble and went with line voltage as there are fewer issues to consider, especially when dimming.


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post #7 of 19 Old 05-11-2012, 10:59 AM
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Be very careful when designing with remote transformers on LV 12VDC systems. Gauge is a very, very big factor. You cannot wire like a normal line voltage ckt.


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post #8 of 19 Old 05-12-2012, 10:25 AM - Thread Starter
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Thanks so much for your comments so far! As a hobbyist, I want to try the low voltage, but I will probably go with line voltage for my lighting in the theater for the practicality.

Can anyone talk about any experiences you've had with buzzing while dimming, either line or low voltage, and what you found out to be the problem? How do you:

A) help prevent buzzing

B) Diagnose and fix it if it's a problem

Thanks!

Electrical engineer by education. Currently a system engineer. I like home automation, theaters, and blinking lights.
Someday it'll be more of an actual hobby - if my employer would ever let me go home!

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post #9 of 19 Old 05-13-2012, 02:58 AM
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We have 123 lights fittings in our place (some have 2 globes). All low voltage, in the 3 years we've been here I have replaced 4 bulbs. They use GE Constant Color Globes.

Spend the money upfront and forget about them.

Oh and nearly every fitting is hooked up to a dimmer and they're all silent

Peter the Greek


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post #10 of 19 Old 05-13-2012, 07:49 AM
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Tech Lighting has a wire size table here.

12 volt 300 watt:
5 ft = 10 ga.
6-15 ft = 6 ga.
16-20 ft = 4 ga.
21-40 ft = 1 ga.
41-60 ft = 1/0 ga.
61-90 ft = 3/0 ga.

That assumes THHN wire and 3% voltage drop.

Those are some big wires. Landscape wire is not rated for in-wall use.

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post #11 of 19 Old 05-13-2012, 12:46 PM
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The trick is to home run each 50w fixture so you can use normal gauges and get decent distances. Star config instead of daisy chain.


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post #12 of 19 Old 05-13-2012, 12:47 PM
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Quote:
Originally Posted by Elill View Post

We have 123 lights fittings in our place (some have 2 globes). All low voltage, in the 3 years we've been here I have replaced 4 bulbs. They use GE Constant Color Globes.

Spend the money upfront and forget about them.

Oh and nearly every fitting is hooked up to a dimmer and they're all silent

Not familiar with them. Link?


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post #13 of 19 Old 05-14-2012, 08:26 PM - Thread Starter
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Quote:
Originally Posted by GetGray View Post

Not familiar with them. Link?

You mean the fixtures, or the GE constant color bulbs?

I found this on the GE bulbs:

Very Long GE Lighting URL

This seemed to give some info also:

http://www.blocklighting.com/c-605-g...16-lights.aspx

Electrical engineer by education. Currently a system engineer. I like home automation, theaters, and blinking lights.
Someday it'll be more of an actual hobby - if my employer would ever let me go home!

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post #14 of 19 Old 05-14-2012, 08:59 PM
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Yep, the globes not the actual fittings. I cant seem to access those links.

3 things with lights:
- Fitting
- Globes
- Transformers

Poor fittings will cause problems between the globe and the transformer, regardless of how good the other parts are.

I think Dennis mentioned that you just need good quality transformers, I cant recommend on for you as in Australia the best thing is called a "possum" which is a local product.

The GE Globes we use wont change colour as they heat up, this is a common point of failure in cheap globes. Problems with the filaments etc.

Best of luck with it.

Peter the Greek


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post #15 of 19 Old 05-15-2012, 03:31 PM
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Quote:
Originally Posted by Elill View Post

We have 123 lights fittings

I meant the fixtures. But I didn't notice before you were in AU so nevermind


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post #16 of 19 Old 05-15-2012, 04:27 PM
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Quote:
Originally Posted by GetGray View Post

I meant the fixtures. But I didn't notice before you were in AU so nevermind

Well if you're ever planning on a move , speak with Tovo Lighting - superb products and even better people

Peter the Greek


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post #17 of 19 Old 05-10-2013, 09:38 AM
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and where is the most common and code approved location to mount the power supply for low voltage lighting systems?

are y'all putting them in the;
soffit
A/V rack
within a hidden electrical panel
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post #18 of 19 Old 05-10-2013, 10:06 AM
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My 12V transformer (and my Lutron Dimmers as well) is inside my soffit. My soffit has a fabric bottom and I have a matching fabric covered access panel that works like a drop ceiling tile to get to it. In other theaters I work on I'd say the more common place is either individual transformers located with the fixture(s), or a common transformer loated in an equipment closet or adjoining utility room. You have to be careful with LV wiring lengths though, they are a big factor you need to consider. FOr similar wattage requirements, due to the low voltage, the amperage is much higher and wire losses are significant.

Edit: I see I mentioned that before but can't hurt to repeat.


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post #19 of 19 Old 08-06-2013, 03:44 PM - Thread Starter
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Quote:
Originally Posted by Andy611 View Post

and where is the most common and code approved location to mount the power supply for low voltage lighting systems?

are y'all putting them in the;
soffit
A/V rack
within a hidden electrical panel

I have a 16x20x4 junction box that I pulled all my lighting runs and switch runs to, so I could modify which switches controlled which lights. I made it bigger so I could put the transformers in the bottom of it if I decide to go 12V. My soffits are drywalled so that isn't an option for me.

Electrical engineer by education. Currently a system engineer. I like home automation, theaters, and blinking lights.
Someday it'll be more of an actual hobby - if my employer would ever let me go home!

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