I'm installing some track 12 in a customers home and was wondering if I could use 16-2 (w outer jacket,like speaker wire)that I have left over from another job. This question is not about wire size and watts or amps either.

As a wild guess, NO.
Substantiation....not enough information, and yes, watts, amps is pertinent to your question along with more details.

BTW, what is "track-12"

John

I was wondering that, too. I googled it, and came up with:
I'm still trying to figure out what you use the 16-2 for.

Track-12 is a small low voltage track from Juno. It is fed from a 12 volt transformer and low voltage lights can be connected directly to the track with out the use of individual transformers.

If this wiring is going to be installed in the walls or ceiling article 411 requires a chapter 3 wiring method (NM, MC, EMT, ETC.). If this wiring is not goi9ng to be concealed low voltage cable could be used but remember the proper overcurrent protection must be used to protect the wire. Most magnetic transformers use at least 15 amp circuit breakers so a minimum of 14 AWG wire must be used.

Edited to add link: http://www.junolighting.com/productinfo/trac_t12_intro.asp

Curt


[This message has been edited by caselec (edited 12-03-2004).]

No you can't use 16-2........once you hit the transformer and switch to DC the farther away you get the more problems you have. The more lights you put on your load the more amps you draw. The farther you get from the transformer the dimmer the lights get from voltage drop. You can solve these problems by using the correct wire size. Should be 12 minimum.....but better to go with 10 gauge if your anywhere near 15 or 20 feet away from the transformer.

bot540


Why do you think that?

Low voltage does not mean low current and many times it means high current.

I followed the link to the Track 12 components and they show transformers for it capable of 2.5 to 20 amps of output power. Which one are you using, how many VA?

At a minimum you must size the wires for low voltage lighting the same way as line voltage.

As a design issue you also should consider voltage drop as kinetic has pointed out.

Wire size aside as has been pointed out you must use a chapter 3 wiring method (NM, MC, etc) if you will be concealing the wire.


There is a change coming in 2005 in this section for class 2 power supplies.

Bob

kinetic


I would say you shouldn't use 16/2 but you can with the proper OCP. The NEC does not care if there is voltage drop only that the conductor is protected at or below the conductors rating.

Voltage drop is strictly a design issue.

As a side note most, if not all low voltage lighting systems run AC power.

Bob

I often use remote transformers for low voltage lighting and will most often use #12 - #8, and once #6. Depending on the fixtures and collective load/wattage/amperage of each circuit section, and especially voltage drop. (Not to mention tranformer type and dimmer types.) Your best tool for installing LV lighting is a calculator. Granted you're probably refering to a small section of track, and only a few lamps on it, with the transformer relitively close. Dare I say it, its the same animal. It might look really cool when you turn it on, but you'll feel really silly calling the fire department.

My inspectors for this area would have you pull out anything short of chapter 3 methods. But as far as any method you use I would suggest a 90 degree or better wire, as the fittings on these have a tendancy to get hot if anything short of properly torqued. I often will leave them on for a while and check the fittings for heating after installation.

And iwire, voltage drop is not a design issue it is a safety issue. These little do dads (meaning the fixture itself) will self destruct with improper voltage. I've seen some that have nearly caught fire, and completely melted. This particular track type of design, the fittings will often fuse together from the heat if improperly seated. And, they give you a handy VD calculation reminder with the listed transformers you must use with this fixture. http://www.junolighting.com/pdf/spec/D3_1_2.pdf

Scott


Well I strongly disagree and that is supported by the NECs silence on voltage drop.

FPNs are strictly suggestions, good ones, but voluntary none the less.

Two questions

1)Show me where voltage drop for any lighting system is referenced in the NEC other than 110.3(B).

2)I have no idea what you mean by self destruct with low voltage.

All the lamps I see in the link for track 12 are incandescent type lamps, they run cooler, draw less current and last longer supplied by less voltage.

Shoot, you can dim these lamps with a dimmer matched to the power supply.

An argument could be made that the lamps and fixtures are safer run under voltage. (Not the power supplies)

For what it's worth we we use 10 to 8 AWG MC cable depending on distance and load when feeding low volt lighting.

Bob



[This message has been edited by iwire (edited 12-04-2004).]

"Scott"-Hehe
(Despite evidence here at ECN to the contrary, not everybody from CA is named Scott- It just seems that way. )

BTW, bots are worms (fly larvae) that grow in the stomach and intestines of a horse, and they'd love to get a load of Track 12, a feed supplement.
(no offense meant to bot540)



[This message has been edited by electure (edited 12-04-2004).]

DOH!

e57 I am sorry about that.

Bob

Mornin, Bob!
I'm only funnin'-got to go to work now

Thanks for the replies. I wasn't asking about watts or amps because the track was only going to have three heads a total of 105 watts or close to 10amps(16 awg being good for 12.5a). The reason I asked this question is because the track will be installed in a kitchen with a fancy exposed beam ceiling. The wire run is about 10' and would have to go through at least 5 beams. I don't want the wire to be that noticeable. Has any one had an installation like this or have any ideas? Also what kind of wire would you recommend? Thanks.

bot is short for botanist, which is my hobby

Bob did you think I screwed up your off-line name again? (You must be flashing back to the last I actually DID do that. )

I occasional get to see the results of others work, where they have not considered voltage drop, or apmerage on these types of track, and it is not pretty. For instance a GC didn't like what we would have charged him for remoting 300 watts @ 100 feet. So he did it himself with 14/2 romex. Called us back to fix it for him. Each track head melted the connection in the track to the point of being charred, and melted the 14/2 until it shorted. None the less, it was not to be saved, as the job could not be re-pulled. And, I have also seen the results of "Designers" do it yourself work as well, also not pretty. One ran about 24' of track with 10 50Watt heads on it, and remoted 50' on #12. They think, "Its low voltage, its a DYI job." They call to ask why it is smoking!

And if you look at the spec sheet for most of the transformers that this track is listed to use (Using other transformers is a listing violation. They tied the track and tranny in the listing....), it clearly states: "Note: Remoting more than 5' is not recommended due to voltage drop." under the picture of each one. For the transformers capable for longer remoting it has an example of VD calc's for choosing the transformer. (bottom of the page) http://www.junolighting.com/pdf/spec/D3_1_2.pdf

bot540, personally I would suggest taking 120v to the location and using this transformer: Catalog Number TL547WH, TL547BL. Or remoting with a TL549BL, and using #12 or larger. Track is an invitaion to the customer to add more heads without concern about load limitations. Or, you can switch to 24v and have fewer worries about remoting with a TL551-24V. One should also take care in choosing a dimmer for this as well. Some (non-clipping types) will lower the voltage slightly in the proccess of dimming, and put you over the limitation of 16ga.

Well we will have to agree to disagre, because reducing the voltage to incandescent lamps will not damage the lamps, sockets, fixtures, or track.

If it did dimmers would be out of the question.

When you reduce the voltage to incandesent lamps the current also drops.

On the other hand overloading the supply cable will lead to heating.

300 Watts at 12 volts is 25 amps so a 14/2 will be warm.

I do agree we should (and must) follow the instructions that come with the lighting system.

Bob

At 100 feet, they barely turned on, just melted.

300W / 12V = 25A

2 X 100' X 3.07 (Table 8) X 25a / 1000 = 15.35 / 12 = 1.279 = 128%VD

The circuit would have required #6, and should have been boosted at the transformer a few volts.

As I said it is a design issue only.

I do not know why your fixtures had a problem but it was not caused by voltage drop.

Less volts at the fixture means less current and heat at the fixture.

We just are not going to see eye to eye on this.

If this was a safety issue don't you think the NEC would address it?

Here is just a wild guess, you said this had been installed by an amateur. Is it possible incorrect installation and loose connections where the culprit and you just assumed it was caused by voltage drop?

I do not mean any disrespect in that.

I am very curious how you would explain why my dining room light (line voltage) does not self destruct when I reduce the voltage to it with a wall dimmer. Or why low volt lighting systems I have installed worked fine on dimmers that reduce the voltage to the fixtures?


Bob

I replaced some selfdestructing t-12 not long ago. Customer had called fire department because of smoke in the kitchen. The juno flex corners were not tight or loosened then thens started melting. There flex corners use a pretined #12 wire. IMO the tinned wire does not have any compression under the small screw where stranded copper has some squish.

One more time.... (Basic ohms law)
300W / 12V = 25A
300W / 120V = 2.5A

Volts down = Amps up
Voltage up = Amps down

When the resulting amperage is applied to the Voltage drop calculation...

300W / 12V = 25A

2 X 100' X 3.07 (Table 8) X 25a / 1000 = 15.35 / 12 = 1.279 = 128%VD
(its over 100%, so at some point voltage hit zero under a 300W load, the result would be very high heat and amperage. 300W / 0.001v = ?)

The same with 120 Volts:

300W / 120V = 2.5A

2 X 100' X 3.07 (Table 8) X 2.5a / 1000 = 1.535 / 120 = .01279 = 1%VD A big difference from 128%.

Now for dimmers, most modern ones are "clipping" type, as opposed to resitance type. The peak voltage is relitively the same, as it only clips off part of the sine wave, creating a dimmed effect. The part of the sine wave it clips off is the area where voltage is lowest, that way the fixture never really sees that low voltage / high amperage part of the sine wave. Thats why dimmed lamps last longer, and your dining room light doesn't self destruct. They are simular to the sine wave on this: http://www.lutron.com/product_technical/pdf/LutronDimmingBasics.pdf

But, if you used an older resistance type dimmer, or incandesant dimmer on magnetic low voltage, you might have some problems.

As for the NEC 210.19 FPN #4, although not mandatory, is a clear warning about the issue. Seeing that the NEC deals offen with voltages 120 and above it isn't so much an issue. But at 12 volts voltage drop is ten times higher, I could see it being added to 411 in the future.

Mark,

The wattage of incandescent lamps changes with the amount of voltage applied. If you reduce the voltage the current does not increase. Sometime look at a package for 130 volt lamps which will list one wattage for 130 volts and a lower wattage if used on 120 volts. The same applies to any resistive load. A typical household range will have a higher wattage rating when connected at 240 volts than when connected to 208 volts. With inductive loads such as motors the current does increase as the voltage decreases.

Curt


[This message has been edited by caselec (edited 12-05-2004).]

Mark you are correct it is basic ohms law lets take a look.

Lets say the circuit is 300 watts at 12 volts

300 watts / 12 volts = 25 amps

12 volts / 25 amps = 0.48 ohms

Now we know that the collection of lamps has a total resistance of 0.48 ohms

Now drop the voltage to 10 volts

10 volts / 0.48 ohms = 20.8 amps

Drop the voltage to 3 volts

3 volts / 0.48 ohms = 6.25 amps.

Drop the voltage all the way down to 1 volt

1 volt / 0.48 ohms = 2.08 amps

As far as the dimmers, I understand how a modern dimmer works, it does not matter the effect is the same.

Bob

Bob, its apples and oranges, both are fruit.

Your describtion of the apple is fine. (What happens at the lamp)

I'm talking about the lemon. (The length of circuit between the source and load, which includes the track itself.)

I guess we will agree to dis-agree.....

[This message has been edited by e57 (edited 12-06-2004).]

Mark It is not apples and oranges (well our thoughts are )

You said


Not true for this load.

You also said the problem was melted fixtures

I have shown that the current and heat would be less at the fixture.

Now you say the problem is in the circuit feeding the fixture.

Yes 14 AWG NM is to small from a safety and design stand point for a 25 amp load of any voltage.

Change it to 10 AWG NM and the safety issue is gone even though the design issue is still there.

If we used 10 AWG for the circuit in question we would be NEC compliant even though we would have 6 volts or 50% voltage drop.

The fixtures would be very dim but there would be no safety issue, the tracks, fixtures and power supplies would be fine.

The lamps would last many years at this reduced voltage.

If you want to leave it as a disagreement that is fine. Perhaps some other members can chime in and explain it in a different way.

Bob

Bob's explanation is right on the money (and he and I have agreed to disagree from way back.)
There's nothing I could add that would make it any easier to understand.
btw-AC impedance DC resistance

You don't switch to DC with a transformer. All non-battery powered 12V lighting I've worked on has been AC.