Dimming Wiring

[steve66]

Can 0-10 Volt dimming wires be ran in the same conduit with 208V power conductors? Can someone provide a code reference?

Is this one of the cases where the low voltage wiring can be reclassified as power wiring, and treated as such?

This is for LED outdoor lighting, so I'm dealing with long underground conduit runs.

While we are on the subject, I'm not sure where the 0-10V signal comes from. Is it supplied by the light fixtures?

That seems odd, because every light would be putting voltage on the same pair of wires.

Maybe each one outputs a constant current, and the voltage developed across the dimmer is the signal the light uses to determine its brightness? But again, adding more than one light seems like it would change everything. Two light would develop twice the voltage of one.

 

[richie921]

Whether or not the dimming conductors can be run in the same raceway as the power conductors depends on the classification of the dimming circuit. Class 1 can run with the power conductors while class 2 can not. Class 1 or 2 depends on sink/source assignment of the control and ballast/driver. Many class 2 ballasts/drivers can be installed as a Class 1 circuit as long as its rated as such, your jurisdiction allows it, and you follow the NEC requirements. I would refer to the literature provided by the mfg of the equipment you are using.

Sent from my SM-G935P using Tapatalk

 

[Dennis Alwon]

I know that Southwire has an mc cable that is made specifically for this application.

 

[steve66]

Whether or not the dimming conductors can be run in the same raceway as the power conductors depends on the classification of the dimming circuit. Class 1 can run with the power conductors while class 2 can not. Class 1 or 2 depends on sink/source assignment of the control and ballast/driver. Many class 2 ballasts/drivers can be installed as a Class 1 circuit as long as its rated as such, your jurisdiction allows it, and you follow the NEC requirements. I would refer to the literature provided by the mfg of the equipment you are using.

Sent from my SM-G935P using Tapatalk

So does anyone know what class this would be? I have never seen specs for a LED dimmer that state if the dimming wiring is class 1, 2, or 3. Class 1 is 30-1000V, so it can't be class 1.

I know that Southwire has an mc cable that is made specifically for this application.

Yes, and that makes me think they need to be separated from the power conductors.

 

[RB1]

As I understand it 0-10V dimming circuits are Class 2 circuits. Section 725.130 Exception No. 2 permits Class 2 circuits to be reclassified and installed as Class 1 circuits where the marking required in 725.124 are eliminated. That might be an issue with a listed dimming panel.

The Southwire MC cable has a flexible tubing around the Class 2 circuit conductors as permitted by 725.136(I)(2).

 

[Fnewman]

Most of the 0-10 v dimmable LED floodlights I have seen have the driver integrated into the housing in such a way that separating the power and dimming leads is not really possible. I suppose the external wiring could be run separately, but sooner or later they will be in a common enclosure.

 

[GoldDigger]

As I understand it 0-10V dimming circuits are Class 2 circuits. Section 725.130 Exception No. 2 permits Class 2 circuits to be reclassified and installed as Class 1 circuits where the marking required in 725.124 are eliminated. That might be an issue with a listed dimming panel.

The Southwire MC cable has a flexible tubing around the Class 2 circuit conductors as permitted by 725.136(I)(2).

My understanding is that Class 2 has two areas of application:
1. Sources: A Class 2 voltage/power source has a strict limit on voltage/current/wattage and must be NRTL listed and marked as Class 2.
2. Sinks: A device that accepts input (control or power) over a low voltage circuit can be listed for use ONLY with a Class 2 source or it may be listed for use with either a Class 1 or a Class 2 source. These ratings are based on the ability of the device to safely tolerate different levels of applied power. (It may fail when exposed to Class 1 voltages, but if so it will at least fail safely. Without that Class 1 testing and listing there is no assurance of safety.)

If you remove the Class 2 markings from a source you can then reclassify the circuit that it drives as Class 1 and use Chapter 3 wiring methods and combine the low voltage limited power wires with power and lighting wires subject to a few more Code constraints.
But if the controlled devices (sinks) are listed only for use with Class 2 drivers you cannot make that reclassification.

The premise, as I understand it, is that by relaxing the wiring requirements from Class 2 to Class 1 you are increasing the risk that the sinks will be subjected to a higher than Class 2 input, and that is not allowed as long as the device itself is NRTL listed only for Class 2 environments.

 

[steve66]

All good responses. Thanks for the replies.

It looks to me like reclassifying the wiring allows it to be ran with the power conductors. I think this makes sense, because the 0-10 V signal is derived from the power to the lights (anywhere from 120 V to 480V), so it seems more likely that a driver failure would energize the wiring, than a short inside the conduit.

I'm still a little vague on how multiple lights all share the same pair of 0-10V wires.

 

[ptonsparky]

All good responses. Thanks for the replies.

It looks to me like reclassifying the wiring allows it to be ran with the power conductors. I think this makes sense, because the 0-10 V signal is derived from the power to the lights (anywhere from 120 V to 480V), so it seems more likely that a driver failure would energize the wiring, than a short inside the conduit.

I'm still a little vague on how multiple lights all share the same pair of 0-10V wires.

I believe the 0-10 comes from a different source. The dimmer.

 

[steve66]

I believe the 0-10 comes from a different source. The dimmer.

Right, that makes sense. Power goes to the dimmer and then to the lights. So the dimmer can generate the 0-10V signal.

The need for the power to go through the dimmer quashed my plans to use 3 phase lighting circuits.

 

[Dennis Alwon]

Right, that makes sense. Power goes to the dimmer and then to the lights. So the dimmer can generate the 0-10V signal.

The need for the power to go through the dimmer quashed my plans to use 3 phase lighting circuits.

Usually with 0-10v the light gets a constant 110v and the dimming controls the intensity.

 

[Fnewman]

The LED world has many more variations than conventional lighting, but a common thread to remember is that LEDs are basically current (ma) driven with the driver packages functioning either as a source or sink. A typical wall mounted 0-10v dimmer (Leviton, Lutron, etc.) has a 120v power source. A 0-10v output and a switched 120v output to the fixture driver. It also usually has an integral off-on switch because 0v output does not always equal 0 light output and doesn't completely disconnect the driver. The number of fixtures that can be controlled by such a device is limited to the amount of current it can source or sink

 

[lordofthisworld]

Can 0-10 Volt dimming wires be ran in the same conduit with 208V power conductors? Can someone provide a code reference?

Is this one of the cases where the low voltage wiring can be reclassified as power wiring, and treated as such?

This is for LED outdoor lighting, so I'm dealing with long underground conduit runs.

While we are on the subject, I'm not sure where the 0-10V signal comes from. Is it supplied by the light fixtures?

That seems odd, because every light would be putting voltage on the same pair of wires.

Maybe each one outputs a constant current, and the voltage developed across the dimmer is the signal the light uses to determine its brightness? But again, adding more than one light seems like it would change everything. Two light would develop twice the voltage of one.

You probably want to get luminary wire where the mc has power conductors plus the 0-10V dimming wires.

 

[lordofthisworld]

Can 0-10 Volt dimming wires be ran in the same conduit with 208V power conductors? Can someone provide a code reference?

Is this one of the cases where the low voltage wiring can be reclassified as power wiring, and treated as such?

This is for LED outdoor lighting, so I'm dealing with long underground conduit runs.

While we are on the subject, I'm not sure where the 0-10V signal comes from. Is it supplied by the light fixtures?

That seems odd, because every light would be putting voltage on the same pair of wires.

Maybe each one outputs a constant current, and the voltage developed across the dimmer is the signal the light uses to determine its brightness? But again, adding more than one light seems like it would change everything. Two light would develop twice the voltage of one.

Also, As long as the insulation is the same rating as the power, you can have it in the same conduit.

 

[GoldDigger]

Also, As long as the insulation is the same rating as the power, you can have it in the same conduit.

Unless there is an issue with a strict Class 2 requirement.
The other suggested way to deal with it is to use a cable that has a separate internal sheath or shield that separates the control wires from the power wires.

 

[steve66]

Usually with 0-10v the light gets a constant 110v and the dimming controls the intensity.

Yes, and that had me thinking I could easily control lights on different circuits - even lights that are supplied with different voltages or phases, all from the same dimmer. So I thought I could connect a whole string of lights to a 208V, 3 phase breaker. I would just power the lights, and connect all the 0-10 V wires to a single dimmer.

But all the cut sheets show power going through the dimmer, and then to the fixture:

http://www.acuitybrands.com/product...roducts/Synergy/48057/document/ISD-BC_pdf.pdf

And they all seem to be slash voltage rated 120/277V, and they all show a neutral connection. None specifically state they work with 208V, and none that I have found say you can use them to control lights on different circuits.

The Leviton Renoir lists 120/230/277V, but not 208 or 240V, and it always shows a neutral wire:

http://www.leviton.com/en/docs/Selection+Guide-Renoir+II.pdf

So this kind of killed my plans to use 208V, 3 phase circuits.

 

[hbiss]

Can 0-10 Volt dimming wires be ran in the same conduit with 208V power conductors? ... This is for LED outdoor lighting, so I'm dealing with long underground conduit runs.

We've just come to terms with indoor dimming through the introduction of "luminary cable" as mentioned. Unfortunately this cable is not wet location listed so it doesn't help you. Keep in mind that it was because of Code prohibitions on running the 0-10v control wiring with line voltage that this cable was developed so if it could be done otherwise these companies wouldn't have spent the money to make this cable. So now you have a unique dimming application where the control wiring needs to be run with the line voltage underground through conduit. I think the only way to do that is to run a large enough conduit and pull UF for the line voltage and tray cable for the control. I would use luminary cable within the structure and transition to the UG in a junction box on the outside of the structure.

That said, it sounds like you have other concerns about the voltage and multiple dimming arrangements that you should have answered by the manufacturer of the drivers.

-Hal

 

[wwhitney]

Can Class 2 conductors be run as a Chapter 3 cable method inside conduit with individual power conductors? E.g. UF cable inside a conduit with THWN conductors. That seems comparable to what the "luminary" cable is doing.

Cheers, Wayne

 

[hbiss]

Yes. You could use UF for the line voltage and THWN conductors for the LV. I'm just thinking that 18/2 tray cable is easier to pull. Heck, you could use two runs of UF if you wanted to.

-Hal

 

[wwhitney]

Yes. You could use UF for the line voltage and THWN conductors for the LV.

I was proposing UF for the LV (or tray cable if you like) and THWN for the line voltage. Still OK?

I'm assuming that the line voltage conductors will be bigger/more numerous than the LV conductors, so conduit fill would be impacted less by putting the LV conductors into a cable, rather than putting the line voltage conductors into a cable.

Cheers, Wayne